School Science Lessons
Topic 16 Organic chemistry, tests for organic compounds
2012-05-17 SPwp
Please send comments to: J.Elfick@uq.edu.au See: IUPAC, Nomenclature of Organic Chemistry (website) Table of contents 16.1.0 Organic chemistry 16.4.5.0 Tests for organic compounds 16.1.5.7 Acid anhydrides, acyl anhydrides, anhydrides,
[RCO-O-COR' (R(C=O)O(C=O)R')] 16.1.5.5 Acyl halides, group: (-CO.X), X = halogen
atom, acid chloride, acid chlorides group: (-COCl), Suffix: -oyl, chloride 16.1.5.6.1 Acrylamide, 2-propenamide, ethylene
carboxamide, acrylic amide, vinyl amide 16.1.1 Acyclic hydrocarbons, alkanes, alkenes,
alkynes 16.1.01 Addition reactions 16.1.3.0 Alcohols, phenols, thiols 16.1.3.1a Alcohol, Ethanol safety 16.3.1.0 Aldehydes, ketones, quinones, Aldehydes
group: -CHO, Suffix: -al 16.1.5.6 Amides, acid amides group: (-CONH2,
RCONH2), Suffix: -amide 16.1.5.6.01 Physostigmine 16.2.4.3 Amines, aliphatic amines, (RNH2-),
R = alkyl group, ionization reaction of methylamine Carbamates 16.2.3.1 Carbides (C4-), (carbon + metal) 16.3.8.0 Carboxylic acids and fatty
acids 16.4.1.01 Carbonyls 16.2.4.3.2 Chloramines in swimming
pools 16.2.10 Coal tar products, creosote 16.2.4.2.1 Cyanamides, inorganic, (CN22-),
ionization reaction of methylamine, cyanic acid, melamine 16.2.4.7 Cyanocrylates [(CH2)C(CN)COOR],
"Superglue" 16.4.4 EDTA, ethylenediaminetetraacetic
acid, C10H16N2O8 16.5.1.0 Esters, derivatives
of fatty acids (RCOOR'), esters group: (-COOR), Suffix: (-oate) 16.1.1b Ethane, (C2H6),
prepare ethane 16.2.4.3.1 Ethylenediamine 16.3.5.0 Fluorescent liquids 16.2.2 Halogen compounds, haloalkanes, (alkyl halides),
halogen derivatives 1.0 Chlorine 16.14.0 Dioxins, Agent orange, polyvinyl
chloride 2.0 Iodine 3.0 Bromine 12.19.5.2 Methyl bromide, bromoethane,
CH3Br 4.0 Fluorine 16.1.5.8 Imides, imido group: (-CONHCO-), (R1CO-NH-COR2) 16.2.4.3a Imines, imino group: -NH- in a ring,
or =NH 16.2.4.2 Nitriles (acid nitriles, alkyl cyanides,
cyanides), (-CN, RC≡N), (note triple bond), Cyanide ion: CN- 16.2.4.5 Nitrites, (NO2-), dioxonitrate
ion, salts or esters of nitrous acid, (O=NOH), Nitrites group: -C=N, Suffix:
-nitrite 16.2.4.4 Nitroalkanes, (nitroparaffins), (CnH2n+1NO2) 16.2.4 Nitrogen compounds, one atom of nitrogen 16.2.5 Nitrogen compounds, two or more nitrogen
atoms 16.2.5 Nitrogen compounds,
two or more nitrogen atoms 16.2.5.1 Azide compounds 16.2.5.2 Azo compounds 16.2.5.3 Diazo compounds 16.2.5.4 Phenylhydrozone compounds
16.2.3 Organometal compounds,
prefix the metal with: organo- 16.1.03 Oxidation reactions, loss of electrons 16.2.4.6 Oximes (hydrox-imino-alkanes), Group:
(C:NOH) 16.2.6 Phosphorous compounds, organophosphorus
insecticides 16.1.00 Prepare organic compounds: addition,
substitution, oxidation, reduction 3.32.0 Prepare gases with a gas generation
apparatus 16.6.1.1 Proteins, peptides, amino
acids 16.1.5.3 Salts, organic salts, e.g. sodium ethanoate,
(sodium acetate, CH3COONa), (ammonium acetate, CH3COONH4) 16.2.8 Sulfur compounds 16.1.1 Acyclic hydrocarbons
16.1.1 Acyclic hydrocarbons, alkanes, alkenes, alkynes 16.1.1.1 Alkanes, (CnH2n+2),
paraffins 16.1.1.1b Arenes 16.1.1.1b Benzene 16.1.1d Butane (C4H10), prepare
butane, combustion of butane 16.1.1.1a Cycloalkanes 16.1.1b Ethane, (C2H6),
prepare ethane 16.1.1f Hexane, (C6H14) 16.1.1g Heptane, (C7H16) LPG (liquefied petroleum gas, LP gas) 16.1.1a Methane, (CH4), prepare methane
gas 16.1.1a.01 Methane, Prepare methane gas 16.1.1a.2 Methane with chlorine 3.39.1 Methane with steam Natural gas Natural gas (Methane) 16.1.1h Octane, (C8H18),
octane number Octadecan-1-ol, C18H38O Octanol 16.1.1e Pentane, (C5H12) 16.1.1c Propane, (C3H8)
3.41.4 Reduce copper oxide with natural
gas, methane 16.1.1a.02 Tests for methane gas, burn methane 16.1.1.2 Alkenes, (CnH2n),
olefins 16.1.1.2.1 Prepare ethene, (ethylene), C2H4 16.1.1.2.2 Dienes, isoprene units 16.1.1.3 Alkynes, (CnH2n-2),
acetylenes 16.1.1.3.1 Prepare ethyne (acetylene) 16.4.6 Tests for gases from burning hydrocarbons,
oxyacetylene welding
16.1.1.1b
Arenes, benzene 16.1.1.1d Friedel-Crafts reaction 16.1.1.1c Nitration 16.1.3.0 Alcohols,
phenols, thiols
16.1.3.0 Alcohols, phenols, thiols, ethers, epoxy compounds, acetates
(ethanoates), benzoyls, acetals 16.1.3.A Propanol, propyl alcohol, (C3H7OH) 16.1.3.B Butanol, butyl alcohol, (C4H9OH) 16.1.3.0.1 Dihydric alcohols, glycol 16.1.3.0.2 Trihydric alcohols, glycerol 16.1.3.0.3 Nitroglycerine (UK), nitroglycerin
(USA) 12.12.4 Oxidation of glycerol by potassium
permanganate 16.1.3.1.1 Alcohols, primary, secondary and
tertiary aliphatic alcohols, rubbing alcohol 16.1.3.1.2 Prepare sodium ethoxide 16.1.3.2 Phenols, group: (OH-C), in a benzene
ring, Phenol = (C6H5O6) 19.1.0.4 Polyhydric alcohols 16.1.3.2a Pyrogallol 16.1.3.2.1 Carbolic acid, phenol, TCP, Dettol 16.1.3.2.2 Naphthols 16.1.3.2.3 Cresols 16.1.3.2.4 Resorcinol 16.1 3.2.5 Triclosan, organohalogens 16.1.3.3 Thiols, mercaptans,
thio alcohols, Thioalcohols group: (-SH), Suffix: (-thiol), (SH in an organic
compound) 16.1.3.4 Ethers, group: (-O-), in organic compound 3.4.3.1 Epoxy compounds, (O atoms
in CCO ring), Epoxy resin polymers, thermoset plastics 16.1.3.6 Acetates, (ethanoates), ROAc 16.1.3.7 Benzoyl group, benzene carbonyl group:
(C6H5CO-) 16.1.3.8 Acetals, (alcohol + aldehyde), RCH(OR')2 16.1.12 Fractional distillation
of crude oil 16.1.13 Prepare triodomethane, (iodoform) 16.1.14 Prepare trichloromethane, (chloroform) 16.1.14.1 Reaction of acetone with bleaching powder 16.1.14.2 Reaction of ethyl alcohol with bleaching powder 16.1.12 Fractional distillation
of crude oil
16.1.12 Fractional distillation of crude oil 16.1.12.1 Petroleum gas, (methane, ethane, propane,
butane), LPG 16.1.12.2 Naphtha, (ligroin), processed to make
gasoline 16.1.12.3 Petrol, "gas", gasoline, motor fuel 16.1.12.4 Kerosene, kerosine, paraffin oil, jet
engine fuel, tractor fuel 16.1.12.5 Diesel oil, gas oil or diesel distillate,
diesel fuel, heating oil 16.1.12.6 Lubricating oil, motor oil, grease 16.1.12.7 Paraffin wax, heavy gas, fuel oil 16.1.12.8 Residuals, bitumen, "tar", asphalt,
waxes, petroleum jelly 16.2.8 Sulfur compounds
16.2.8 Sulfur compounds, (For the "thio" prefix, replace oxygen by sulfur,
e.g. thiobenzamide [PhC(=S)NH2])
16.2.8.1 Isothiocyanates, (old name: mustard oil), (RN=C=S), Mustards:
[X(CH2.CH2)2S] 16.2.8.2 Sulfides: RSR, (R not equal to H), Old
name: thioethers
16.2.8.3 Sulfonic acids, group: R-SO2OH, e.g. methanesulfonic acid, CH3SO2OH,
Salts or esters: sulfonates
16.2.8.4 Sulfonium compounds: R3S+, e.g. trimethylsulfonium
chloride [(CH3)3S]+Cl-
16.2.8.5 Thiocyanates: [RC(=O)SN], Salts and esters of thiocyanic acid,
HSCN, e.g. methyl thiocyanate (CH3SC≡N)
16.2.8.6 Silicones: polymeric unbranched siloxanes, Formula: (-OSiR2-)n,
(R not equal to H) 16.2.8.7 Siloxanes 16.2.8.9 Sulfoxide, e.g. dimethyl sulfoxide,
DMSO, (CH3)2SO, C2H6OS, propanethial
S-oxide 16.1.3.3 Thiols, thio-alcohols 16.3.1.0 Aldehydes,
ketones, quinones
16.3.1.0 Aldehydes, ketones, quinones, Aldehydes group: (-CHO), Suffix:
(-al) 16.3.1a Aldehydes, alkanals, (aliphatic aldehydes),
ketones, quinones Metaldehyde 16.3.1 Prepare ethanal, (acetaldehyde), with potassium
dichromate 16.3.2 Prepare ethanal with potassium manganate
(VII) 16.3.3 Oxidation of methanol to methanal using
platinum catalyst 16.3.7.2 Oxidation of glucose with
sodium hydroxide and methylene blue, blue bottle experiment 16.3.7.3 Silver mirror tests for
aldehydes, Tollens' test 16.3.7.0 Fehling's tests for aldehydes
in solution 16.3.7.1 Reducing sugars and nonreducing
sugars 16.3.8 Ketones, Group: (>C=O), Suffix: -one 16.3.9 Diacetyl, 2,3-butanedione 16.3.10.0 Quinones 16.3.10.1 Pindone 9.140 Tests for reducing sugars and
aldehydes, tests for simple sugars, Fehling's test 16.3.5.0 Fluorescent liquids 16.3.5.1 Aesculin, (Escalin) 16.3.5.2 Amido phthalic acid and amido-tarephthalic
acid 16.3.5.3 Eosin, (Eosine) 16.3.5.4 Fluorescein 16.3.5.5 Fraxin 16.3.5.6 Magdala red 16.3.5.7 | Quinine 16.3.5.8 Safranin, (safranine, safranin O, basic
red 2) 16.4.5.0 Tests for organic
compounds 16.3.7.3 Tests for aldehydes, Silver
mirror tests for aldehydes, Tollens' test 9.137 Tests for fats and oils 16.4.6 Tests for gases from burning hydrocarbons,
oxyacetylene welding 16.4.1.0 Tests for organic acids
and alcohols 16.4.5 Tests for proportion of fats
in foods 16.4.7.0 Tests for saturated hydrocarbons,
bromine water test 16.4.8 Tests for saturated hydrocarbons,
alkaline potassium manganate (VII) solution 16.4.9.0 Tests for saturated hydrocarbons,
acidified potassium manganate (VII) solution 16.1.0 Organic chemistry, preparing different compounds See diagram 16.0.0: Organic chemistry functional
groups See diagram 16.0.1: Tetrahedral geometry
of carbon, methane molecule, isobutyl alcohol
Organic chemistry is the chemistry of carbon compounds. Hydrocarbons
contain carbon and hydrogen only. The main types are the alkanes, alkenes
and alkynes. In alkenes and alkynes, addition reactions occur at the double
bonds, =, or triple bonds, ≡.
Be careful! When heating organic chemicals, do not point the test-tube
towards anyone! Organic compounds may suddenly vaporize and spurt out of
the test-tube!
1. Classification by molecular framework
1.1 Acyclic compounds have chains of unbranched or branched carbon atoms
1.2 Carbocyclic compounds have rings of carbon atoms
1.3 Heterocyclic compounds have rings of carbon atoms with one atom in
a ring not carbon, e.g. O, N, S
2. Classification by functional group, e.g. hydroxyl group, OH, is characteristic
of alcohols 16.1.00 Prepare
organic compounds 16.1.01 Addition reactions
Atoms are added to the two atoms of a double bond or triple bond in an
unsaturated compound, also when no atoms are replaced but extra covalent
bonds are formed.
Alkenes (olefins) or alkynes (acetylenes) --> haloalkanes (alkyl halides),
or primary alkanols (alcohols), or secondary alkanols (alcohols)
Example: HCl + CH2CH2 --> CH3CH2Cl 16.1.02 Substitution
reactions (displacement reactions)
Replacement of an atom or group in a molecule by another atom or group Alkanes (paraffins) --> haloalkanes (alkyl halides) --> amines Haloalkanes (alkyl halides) <--> primary alkanols (alcohols), (-CH2-OH) Alkanoic acids --> esters --> amides
Example: CH4 + Cl2 --> CH3Cl + HCl
[chlorination produces chloromethane (methyl chloride) and
HCl.] 16.1.03 Oxidation
reactions - loss of electrons Primary alcohols can be directly oxidized to aldehydes or carboxylic
acids Primary alkanols (alcohols), (-CH2-OH) --> alkanals (aliphatic
aldehydes)
Example: CH3OH + ½ O2 --> CH2O + H2
(Pt catalyst) [Oxidation of methanol to methanal using a platinum catalyst] Alkanals --> alkanoic acids, e.g. butanoic acid, CH3(CH2)2COOH Secondary alkanols (alcohols), (CH3)2CHOH -->
alkanones 16.1.04 Reduction
reactions - gain of electrons Alkanals (aliphatic aldehydes) --> primary alkanols (alcohols), (-CH2-OH)
Example: Add drops of formalin to a test-tube one quarter filled with
Fehling's A and B solutions and heat to boiling. Note the yellow then orange
then red precipitate of copper (I) oxide. The copper from the copper (II)
sulfate solution has been reduced from copper (II) to copper (I). 16.1.1 Acyclic hydrocarbons, alkanes, alkenes,
alkynes
See diagram 16.1.1: Alkanes, alkenes, alkynes | See 10.6.3: Distil crude oil and collect
the fractions
Alkanes, alkenes, alkynes or their derivatives are aliphatic compounds,
i.e. non-cyclic organic compounds.
Acyclic molecules have carbon atoms in chains but not in rings. The chains
may be unbranched or branched. Aromatic compounds contain a benzene ring
in the molecule. Hydrocarbon compounds contain only hydrogen and carbon.
Hydrocarbons are usually colourless and have low solubility in water. Crude
oil is a mixture of hydrocarbons. Hydrocarbons may be saturated, i.e. have
only single bonds, or
unsaturated, i.e. contain multiple bonds, e.g. double
bond =, triple bond ≡.
The iodine value is the number of grams of iodine absorbed by 100 g of
fat or oil to indicate the amount
of unsaturated acids. 16.1.1.1 Alkanes (CnH2n+2),
paraffins
The first 10 unbranched alkanes and molecular formula: methane (CH4),
ethane (C2H6), propane (CH3H8),
butane (CH4H10), pentane (CH5H12),
hexane (CH6H14). heptane (CH7H16),
octane (CH8H18), nonane (CH9H20),
decane (CH10H22).
Alkanes burn in oxygen to give
carbon dioxide and water. Candle wax is a mixture of different alkanes
that are solid at room temperature. Alkanes are usually associated with
natural petroleum deposits and can be distilled from petroleum.
1. Alkanes (paraffins) are saturated hydrocarbons, i.e. all single bonds
between C atoms, have formula CnH2n+2
and names end in "ane". The names of unbranched alkanes come from the number
of carbon atoms. The name of branched alkanes come from the longest chain
of carbon atoms. The hydrocarbon branches, alkyl groups, symbol R, are
formed by removing one hydrogen atom from the alkane and named by changing
the "ane" to "yl", e.g. methane, CH4 to methyl, CH3-,
also "Me". The carbon atoms of the longest continuous name are numbered
starting at the end of the chain closest to the first branch, e.g. an eight
carbon chain with an ethyl group attached to carbon 5 and a methyl group
attached to carbon 3 and carbon 4 is called 5-ethyl-3, 4-dimethyloctane. 16.1.1.1a Cycloalkanes
Cycloalkanes are saturated hydrocarbons with a ring of carbon atoms, e.g.
cyclopropane (the simplest) cyclobutane, cyclopentane, cyclohexane, cycloheptane,
cyclooctane. The position of branches depends on the alphabetical order of
the branch names so that highest in order is attached to carbon 1, e.g. 1-ethyl-2-methylcyclopropane. 16.1.1.1b Arenes, benzene See 16.3.4.0: Aromatics, aromatic
compounds, benzene derivatives, arenes See diagram 16.8.1: Benzene compounds Benzene, C6H6,
has a stable six-sided ring structure. Arenes, e.g. benzene, naphthalene, anthracene, phenanthrene. Arenes do
not mix with water, but they do mix with hydrocarbons and all non-polar
solvents. Arenes usually burn with a smoky flame, as do most aromatic compounds,
because of the high carbon: nitrogen ratio. So when they burn in air, some
carbon soot usually remains in the air. Arenes are called aromatic compounds because the first arenes were isolated
from fragrant oils. However, nowadays aromatic refers to the structure not
the smell. 16.1.1.1c Nitration
The reaction substitutes a hydrogen atom in an arene ring by a -NO2 group.
For example:
Heat benzene with a mixture of nitric and sulfuric acid catalyst in
a Liebig condenser at 330 K.
benzene + HNO3 --> benzene-NO2 + H2O
benzene + NO2+ --> benzene-NO2 + H+
Also, some 1,3-dinitrobenzene may form.
16.1.1.1d Friedel-Crafts
reaction
The reaction substitutes a hydrogen atom in an arene ring of a halogenalkane
by an organic group, R, using aluminium chloride catalyst.
RCl +AlCl3 --> R+ + AlCl4-
For example, benzene with chloromethane forms methylbenzene.
benzene + CH3+ --> benzene-CH3 + H+
CH3Cl +AlCl3 --> CH3+
+ AlCl4- 16.1.1a Methane (CH4), prepare methane
gas See diagram 16.0.1: Tetrahedral geometry of
carbon, methane molecule, isobutyl alcohol
Methane is the simplest alkane. It is colourless and odourless and found
in natural gas and bubbles of methane in swamp water. Fire damp, which causes
explosions in coal mines, is a mixture of methane and air. Methane is found
in large quantities usually associated with petroleum. It has largely displaced
town gas produced from coal. Methanogenic bacteria live in swamps and in
the human gastrointestinal tract where they liberate methane causing flatulence.
After carbon dioxide, methane produced by bacteria in rice paddies may be
the second most important greenhouse gas made by man. They produce methane
gas anaerobically (without oxygen) by removing the electrons from hydrogen
gas. The electrons and H+ ions from hydrogen gas are used to
reduce carbon dioxide to methane. H+ ions combine with the oxygen
from carbon dioxide to form water and electrons move through the steps of
an anaerobic electron transport system to the phosphorylate of ADP to form
ATP. Methane, is a simple asphyxiant. 16.1.1a.01 Prepare methane
gas See diagram 3.32: Collect insoluble gases over
water
Heat 20 g of sodium acetate-3-water in a Pyrex test-tube until the salt
becomes anhydrous. Grind the cooled salt with an equal amount of soda lime
[NaOH + Ca(OH)2] granules in a mortar and pestle. Mix thoroughly
and place the mixture in a Pyrex test-tube. Heat the test-tube and collect
the gas over water.
Be careful! If you do not pull out the delivery tube, heating the water
stops or the water will be "sucked back" into the hot test-tube! For safety,
wrap the test-tube in wire gauze.
CH3COONa + NaOH --> CH4 + Na2CO3
sodium acetate + sodium hydroxide --> methane + sodium carbonate 16.1.1a.02 Tests for methane
gas, burn methane
Light the gas in the test-tube with a glowing splint. The gas burns with
a clear flame.
CH4 + 2O2 --> CO2 + 2H2O
3. Repeat the experiment using glacial acetic acid soaked in glass wool
+ soda lime. 16.1.1a.2 Methane
with chlorine
When a mixture of an alkane and chlorine gas are stored at low temperature
in the dark no reaction occurs. At high temperatures or in sunlight, a
substitution exothermic reaction called chlorination occurs to produce chloromethane,
methyl chloride and HCl.
CH4 + Cl2 --> CH3Cl + HCl
Excess chlorine can produce dichloromethane (methylene chloride) trichloromethane
(chloroform) and tetrachloromethane (carbon tetrachloride). A mixture of
chlorine and methane explodes violently in direct sunlight forming hydrogen
chloride and free
carbon. BE CAREFUL! Do not mix chlorine and
methane!
CH4 (g) + 2Cl2 (g) --> C (s) + 4HCl (g) + energy 16.1.1b Ethane (C2H6), prepare
ethane
Colourless and odourless gas which has properties similar to methane. See 3.32.0: Prepare gases with a gas
generation apparatus | See diagram 16.1.1:
Ethane
Collect insoluble gases over water. (This experiment was called the "wet
asbestos method" because asbestos wool, now not allowed in schools, was
used to soak up the methyl iodide in the test-tube.) Pour 2 cm methyl iodide
in a test-tube. Add 5 g of copper turnings and push it down firmly with
a spatula. Set up the apparatus and heat the mixture.
2CH3I + 2Cu --> C2H6 + Cu2I2 16.1.1c Propane (C3H8)
Colourless liquefied petroleum gas, a bottled gas, b.p. -42.2oC,
catalytic cracking forms propylene 16.1.1cc LPG (liquefied
petroleum gas, LP gas)
LPG is a clean burning fuel and is stored in gas cylinders as bottled
gas. LPG is a simple asphyxiant. It consists of propane (about 95%) together
with varying proportions of butane, propylene and butylene. A bad smelling
compound is added so that the presence of the gas can be easily detected.
Incomplete combustion forms carbon monoxide. Do not search for a gas leak
with a lighted match or lighted taper. Use a soap solution. 16.1.1d Butane (C4H10), prepare
butane, combustion of butane
b.p. -0.5oC, relative density 0.60 at 0oC, is stored
as liquid under pressure in steel cylinders giving Calor gas and cigarette
lighter gas, cigarette lighter fuel is 90% butane, isomer isobutane. See diagram 3.32: Collect insoluble gases over
water, See 3. | See diagram 16.1.1: Butane formula
(This experiment was called the "wet asbestos method" because asbestos
wool, now not allowed in schools, was used to soak up the ethyl iodide
in the test-tube.)
Pour 2 cm ethyl iodide in a test-tube. Add 5 g of copper turnings and
push it down firmly with a spatula. Set up the apparatus and heat the mixture.
2C2H5I + 2Cu --> C4H10
+ Cu2I2
Combustion of butane See
pdf Butane / Oxygen combustion
2C4H10 + 13O2 --> 8CO2
+10H2O + energy 16.1.1e Pentane (C5H12)
b.p. 36.3oC, relative density 0.63, is made by distillation
of petroleum.
16.1.1f Hexane (C6H14)
b.p. 68.7oC, relative density 0.66, exists as five compounds
with same formula, normal hexane, n-hexane, in petrol and petroleum ether
solvent, colourless liquid ethereal odour. "Shellite" (Australia) is 60%
hexane and 40% heptane.
16.1.1g Heptane (C7H16)
b.p. 98oC, relative density 0.68, nine isomers, normal heptane
has similar properties to normal hexane.
16.1.1h Octane (C8H18), Octane
number See diagram 16.1.1h: Octane ratings
b.p. 126oC, relative density 0.702 at 20oC, exists
as eighteen compounds, in petroleum. Isomeric with iso-octane, 2, 2, 4-trimethylpentane
(CH3)3CCH2CH(CH3)2.
Octane number See: 32.5.5.5: Spark plugs, pre-ignition
Some hydrocarbons with unbranched carbon chains prematurely explode in
the cylinder and produce an audible knocking sound or "ping" sound (knocking,
pinking). A scale of "knock property" has isooctane (2, 2, 4-trimethylpentane)
at 100 (a good fuel) and heptane at 0 (a poor fuel). So gasoline with octane
number 80 has the same properties as a mixture of 80% isooctane and 29%
heptane. Octane number is the percentage of iso-octane normal heptane mix
with the same knocking behaviour of the fuel being
tested, so it indicates
the knock rating of a motor fuel. A high octane fuel has a longer self-ignition
delay in motor car engine. In Brisbane, most " family cars" use 91 octane
"unleaded petrol". This is the lowest octane rating of the different petrols
sold in garages.
A high octane rating of a fuel means that it has less tendency to pre-ignite
in a high compression engine. Pre ignition means that, before the spark
plug has fired, the fuel air mixture burns because of the heat created in
the cylinder by compression. Unleaded petrol has the octane rating 98.
Engine compression ratio
4:1
5:1
6:1
7:1
8:1
9:1
10:1
11:1
12:1
Octane number to be knock-free
60
73
81
87
91
95
98
100
102
Octadecan-1-ol, C18H38O,
octadecyl alcohol, 1-octadecanol, stearyl alcohol
Use octadecan-1-ol for melting point curve experiments. Octanol, CH3(CH2)7OH,
1-octanol, octyl alcohol, n-octyl alcohol, octan-1-ol, caprylic alcohol,
Flammable See 3.10.0 Toxicity, Poisons and First
Aid: See Octanol 16.1.1.2 Alkenes (CnH2n),
olefins
ethene (ethylene), (H2C=CH2), amylene, propadiene
(allene), (R2C=C=CR2), dienes buta-1, 2-diene
(CH3CH=C=CH2),
amylene See diagram 16.1.1: Cyclodienes, cis-trans
alkenes
1. Suffix: -ene for C=C (olefin, olefins, olefines) are unsaturated hydrocarbons
with at least one double bond between C atoms, C=C, have formula CnH2n.
Alkenes include ethene (ethylene, C2H4, CH2=CH2),
ethenyl (vinyl CH2=CH-), 3-propenyl (allyl, CH2=CH-CH2-),
e.g. vinyl chloride (chlorethene, CH2CHCl), allyl chloride (3-chloropropene
CH2=CH-CH2Cl). (In the textile trade "olefin" refers
to synthetic fibre, polyolefin fibre, that are long-chain polymers of ethylene
or propylene, i.e. polyethylene (polypropylene, PP). Alkenes decolorize acidified
potassium permanganate solution and bromine solution.
2. The cycloalkenes, cycloolefins, are closed chain, non-aromatic forms,
e.g. cyclopropene,
CH.CH.CH2, cyclobutene, cyclopentene, cyclohexene. 16.1.1.2.1
Prepare ethene (ethylene), C2H4 See 3.32.0: Prepare gases with a gas
generation apparatus
The preparation is an example of the dehydration of an alcohol.
1. Slowly add 10 mL of concentrated sulfuric acid to 5 mL of ethanol and
1 g of powdered aluminium sulfate in the gas preparation apparatus. Be careful!
Pass the gas formed through sodium hydroxide solution to remove sulfur dioxide
and carbon dioxide. Collect the gas over water. Heat only if necessary.
Pass through sulfuric acid as dehydrating agent.
CH3CH2OH -> H2C=CH2 + H2O
2. Add 3 mL ethanol to a plug of glass wool in a
boiling tube. Cover the glass wool with porous pot and heat the porous pot.
C2H5OH --> C2H4 (g) + H2O
3. Prepare ethene (ethylene) with ethanol, breakdown
of ethanol to ethene (ethylene, H2C=CH2). See 3.96: Breakdown of ethanol to ethene
(ethylene)
Alkanes (paraffins) are saturated hydrocarbons. Ethene (ethylene, H2C=CH2), gas is a plant growth
substance. It is produced in wounded, diseased and ripening tissues where
it reacts with auxins to induce fruit ripening and abscission of leaves
or diseased
parts. It is used to ripen stored fruit artificially, e.g.
bananas.
Put some cleaned and dried unglazed porcelain chips in a flask. Add 10
mL of pure ethanol (absolute alcohol). Slowly pour 30 mL of concentrated
sulfuric acid down the sides of the flask. Be careful!
Shake the flask gently
under cool water to avoid alcohol being carbonized because of increase in
temperature. Fit the flask with a thermometer and a delivery tube inserted
in a two-holes rubber stopper. Heat the flask to raise the temperature
quickly to 170oC, then control at 170oC. This heating
procedure is used to increase the use ratio of ethanol and decrease by-products.
Wait until exclusion of the air in the flask and then collect the produced
ethene gas over water. Concentrated sulfuric acid and sodium hydroxide solution
can be used to absorb and remove the small quantities of the ethyl ether
(sulfuric ether) vapour, carbon dioxide and sulfur dioxide present in the
produced ethene.
C2H5OH (l) -> C2H4 (g)
+ H2O at 170oC.
4. Prepare ethene (ethylene), with ethanol, alternative
method See diagram 16.10.3: Prepare ethene
Absorb ethanol in cotton wool and push this to the bottom of a hard glass
test-tube. Pack small pieces of unglazed porcelain in the middle of the
test-tube. Fit a delivery tube to collect ethene gas over water. First heat
the porous pot strongly and then heat gently the cotton wool to produce
some ethanol vapour. This vapour breaks down over the hot porous pot to
produce ethene gas and water vapour. The temperature should be above 170oC
otherwise the reaction produces dimethyl ether. Collect the ethene over
water. Be careful! Disconnect the delivery tube when you stop heating, to
avoid a suck back of water onto the hot porous pot.
16.1.1.2.2 Dienes, isoprene units See diagram 16.1.1.2.2: Isoprene
1. Dienes are alkenes with two double bonds in the molecule.
2. Cumulated dienes have double bonds next to each other.
3. Conjugated dienes have 2 double bonds separated by a single bond:
buta-1,3-diene (CH2:CH.CH:CH2)
Isoprene, 2-methyl-1,3-butadiene, CH2:C(CH3)CH:CH2
4. Cyclodienes
1,3-cyclohexadiene
1,4-cyclohexadiene
5. The 5-carbon isoprene units in natural products have a four carbon
chain and a one carbon branch at
C2, i.e. [C(CC)CC]
Terpenes have linked isoprene units as in natural rubber.
Rosin is a solid amber residue made by the distillation of turpentine
using pine stumps. Natural turpentine contains the terpene called pinene,
C10H16. 16.1.1.3 Alkynes (CnH2n-2),
acetylenes
1. acetylenes: ethyne (acetylene), (C2H2 (HC≡CH),
isoprene, methylene
Suffix: (-yne), for (C≡C), (acetylenes), are unsaturated hydrocarbons
with at least one triple bond (≡), between C atoms, include ethyne (C2H2),
acetylene, (HC≡CH), 3-propargyl (propargyl), (HC≡C-CH2-). Alkynes
decolorize acidified potassium permanganate solution and bromine solution.
2. The cycloalkynes, are closed chain, non-aromatic forms, e.g. cyclooctyne,
C8H12 (the smallest form). 16.1.1.3.1 Prepare ethyne (acetylene) See diagram 16.1.5: Prepare ethyne
The main hazard with calcium carbide is the ignition of air / acetylene
mixtures. A violent explosion may occur, depending on the proportions of
air and acetylene. Acetylene, when undiluted with air, burns with a smoky
flame. Before igniting acetylene, be sure that it is not mixed with air.
Commercial calcium carbide usually contains sulfur and phosphorus compounds
that react with water to form strongly smelling gaseous impurities that
act as a convenient indicator for the presence of acetylene.
1. In a fume cupboard, put a 2 g lump of calcium carbide in a 250 mL beaker.
Add water drop-by-drop. Calcium carbide reacts vigorously with water forming
acetylene gas (ethyne) and releasing a considerable amount of heat. Ignite
the resulting bubbles of acetylene.
2. On a metal tray or shallow container in a fume cupboard, add water
drop-by-drop to one lump of calcium carbide. The water will hiss and the gas
will be produced. The lump will fall to pieces to form a powder of calcium
hydroxide. Do not attempt to ignite the acetylene produced.
3. Put a < 5 g lump of solid calcium carbide in 500 mL of water and
ignite the ethyne produced. Do this experiment outside, with the observers
at least 2 metres away.
4. Formerly, bicycle "carbide lamps" used the following reaction. Put
sand in a dry test-tube and add pieces or lumps (not powder) of calcium dicarbide
(calcium carbide). Add water drop by drop. Collect the gas over water.
CaC2 + 2H2O -> C2H2 + Ca(OH)2
calcium dicarbide + water -> ethyne (acetylene) + calcium hydroxide
5. Collect acetylene from oxy-acetylene equipment
5. Tests for acetylene, (ethyne): Light the gas in the test-tube with
a glowing splint. The gas burns with a smoky flame. 16.4.6 Tests for gases from burning hydrocarbons,
oxyacetylene welding
Hydrocarbons burn in excess air to form carbon dioxide and water. The reaction
is exothermic. Methane burns with a clear flame. Ethene (ethylene) and
ethyne (acetylene) burn with a smoky luminous flame. This flame can be
seen above a chimney at many petrol refineries where excess ethene is burned
off.
Light a natural gas burner or pour drops of cigarette lighter fuel in
an evaporating basin and ignite it. Hold a dry test-tube containing ice over
the burning gas. Water from the combustion condenses on the test-tube. Add
limewater and shake. The milky precipitate shows the presence of carbon
dioxide.
CH4 (g) + 2O2 (g) ---> CO2 (g) + 2H2O
(g)
In insufficient oxygen, the poisonous gas carbon monoxide forms.
2CH4 (g) + 3O2 (g) ---> 2CO (g) + 4H2O
(g) Oxyacetylene welding (oxy-acetylene welding)
In excess air, acetylene (ethyne) burns with a hot white flame. If the
acetylene is mixed with oxygen from separate gas cylinders in an oxy-acetylene
torch, a temperature of 3 500oC can be produced to allow welding
of tubes and pipes. The two ends of the metal objects to be welded are
heated until they begin to melt. Rods of "filler" metal are melted along
the joint then the joint cools and solidifies. The oxyacetylene flame can
burn under water. Also, metal can be preheated with the oxyacetylene flame
then cut with a pure oxygen flame.
2C2H2 (g) + 5O2 (g) ---> 4CO2
(g) + 2H2O (g)
Commercial
Arc welding electrodes, Satin craft 13, 5 kg, 3.2 mm × 380 mm, pack
Arc welding electrodes, Satin craft 13, 5 kg, 2.5 mm × 300 mm, pack
Arc welding electrodes, GP 6012, 5 kg, 3.2 mm × 380 mm, pack
Arc welding electrodes, GP 6012, 5 kg, 2.5 mm × 300 mm, pack
Arc welding mig wires, automatic, autocraft LWI, 15 kg spool, 0.9 mm
Welding gloves, chrome leather, black and gold
Welding goggles, for oxy-acetylene welding, lift up front
Welding helmet, lift up front, head harness
Welding mats, anti-fatigue, non-slip mats, resistant to welding sparks,
700 mm × 800 mm centre piece
Welding mats, anti-fatigue, non-slip mats, resistant to welding sparks,
700 mm × 800 mm end piece
Welding safety apron, chrome leather, reinforced straps, 910 mm × 560
mm
Wire / scratch brush, four rows of steel bristles with wooden handle 16.1.3.0 Alcohols, phenols,
thiols, ethers, epoxy compounds, acetates (ethanoates) benzoyls, acetals
Alcohols are organic compounds with the functional group -OH, but when
attached to an aromatic ring called phenols.
Alcohols, alcohols group: (-OH) Suffix: (ol) primary, secondary and tertiary
aliphatic alcohols, e.g. Primary alcohol, methanol, CH3OH, Secondary
alcohol, propan-2-ol, (CH3)2CHOH, Tertiary alcohol,
2-methylpropan-2-ol, (CH3)3COH
Alcohols, R-OH, are compounds in which a functional group, the hydroxyl
group, -OH, is attached to a saturated carbon atom, e.g. R3COH,
"hydroxyl" refers to the radical HO-. The
"alcohol" in alcoholic beverages is ethanol, ethyl alcohol, CH3CH2OH See diagram 16.0.1: Tetrahedral geometry of
carbon, methane molecule, isobutyl alcohol
Alcohols (ROH), (-ol), alkanols, e.g. methanol (methyl alcohol), (CH3OH),
ethanol (ethyl alcohol), (C2H5OH) 16.1.3.1a Ethanol safety
Do not heat ethanol over an open flame but use a water bath. However,
ethanol may be use in small quantities in alcohol burners to measure heat
of combustion and for reaction with alkanoic acids to form esters.
Ethanol forms violently explosive mixtures with nitric acid and other
oxidizing agents.
Ethanol with acidified dichromate solutions is highly exothermic.
Ethanol reacts violently with potassium.
Alcohol flammability, ethanol > 70% (PG II), < 70% (e.g. 24%) (PG
III), < 24% not a dangerous good 16.1.3.A Propanol
(C3H7OH) has 2 isomers:
1. Propan-1-ol, 1-propanol (n-propyl alcohol), (CH3CH2CH2OH)
2. Propan-2-ol, 2-propanol (iso-propyl alcohol), [CH3CH(OH)CH3] 16.1.3.B Butanol,
butyl alcohol (C4H9OH) has 4 isomers:
1. Butan-1-ol, 1-butanol, n-butanol, n-butyl alcohol, (biobutanol), (a
primary alcohol), product of carbohydrate fermentation, common flavorant
2. Butan-2-ol, 2-butanol, sec-butanol, sec-butyl alcohol, (a secondary
alcohol), product of grain and hops fermentation
3. 2-methylpropan-1-ol, isobutanol, isobutyl alcohol, IBA, 2-methyl-1-propanol,
(CH3)2CHCH2OH, additive to reduce viscosity,
flavouring agent
4. 2-methyl-propan-2-ol, tert-Butanol, tert-butyl alcohol, (simplest
tertiary alcohol), paint remover solvent
5. 2-butoxyethanol, butyl glycol, butyl cellosolve, C4H9OCH2CH2OH,
pH11, in window cleaner "Windex", inks, paint solvents 16.1.3.0.1 Dihydric alcohols,
glycol
The dihydric alcohols, glycols, diols, have two hydroxy groups on different
carbon atoms, e.g. ethane-1,2-diol, ethylene glycol, glycol (HOCH2CH2OH)
butane-1,4-diol [HO(CH2]4OH]
CH2CH2 (oxidation) --> CH2OCH2
(+ water) --> HOCH2CH2OH
ethene (oxidation) --> epoxyethane (+ water) --> ethane-1,2-diol
(glycol, antifreeze) 16.1.3.0.2 Trihydric alcohols,
glycerol
The trihydric alcohols, have three hydroxy groups on different carbon
atoms,
e.g. 1,2,3-trihydoxypropane, glycerol [HOCH2CH(OH)CH2OH] 16.1.3.0.3 Nitroglycerine
(UK), Nitroglycerin (USA)
glycerol + cold mixture of conc. sulfuric acid + nitric acid --> CH2(NO3)CH(NO3)CH2(NO3),
C3H5(ONO2)3, nitroglycerine,
ester of nitric acid
Colourless, insoluble oil, solidifies on cooling, contact explosive,
used to make dynamite, cordite.
Nitroglycerine is a very unstable liquid that explodes if given a slight
shock. It freezes at 13oC but is more likely to explode if solid.
It is used to make safer explosives, e.g. dynamite. It is also used in
very small tablets for the heart condition angina pectoris where people
get out of breath and suffer pain in the chest from over-exertion.
16.1.3.1.1 Alcohols, primary, secondary and tertiary
aliphatic alcohols, rubbing alcohol
Primary alcohols RCH2OH, Secondary alcohols R2CHOH,
Tertiary alcohols R3COH See 3.38: Carbon dioxide and fermentation
for brewing See 16.5.10: Rubbing alcohol, surgical
spirit
1. Primary alcohols, e.g. methanol (methyl alcohol, CH3OH),
propanol (isomer propan-1-ol, n-propyl alcohol, CH3CH2CH2OH),
and butan-1-ol (1-butanol, n-butanol, CH3(CH2)3OH),
have two hydrogen atoms attached to the carbon atom attached to the hydroxyl
group (-OH). So they all have -CH2OH in their molecules. They
can be directly oxidized to aldehydes or carboxylic acids using oxidizing
agents.
(O)R1-CH(OH)-R2 --> R1-C(O)-R2(O)R-CH2OH
--> R-CHO(O)R-CHO --> R-COOH
1.1 Allyl alcohol, CH2:CHCH2OH, prop-2-en-1-ol, 2-propen-1-ol,
Highly toxic by all routes
2. Secondary alcohols, e.g. propan-2-ol (CH3)2CHOH,
rubbing alcohol, isopropyl alcohol and secondary butyl alcohol, butan-2-ol
(CH3CH2CH[CH3]OH), [ or CH3CH(OH)C2H5],
have one hydrogen atom attached to the carbon atom attached to the hydroxyl
group (-OH). So they all have (-CHOH), in their molecules. They can be
slowly oxidized to ketones.
(O)R1-CH(OH)-R2 --> R1-C(O)-R2
3. Tertiary alcohols, e.g. 2-methylpropan-2-ol, 2-methyl-2-propanol (CH3)3COH,
tertiary butyl alcohol has no hydrogen atom attached to the carbon atom
attached to the -OH group. So they all have -COH in their molecules.
4. To one drop of each alcohol in three test-tubes, add saturated potassium
manganate (VII) solution drop by drop with shaking. If decolorization occurs,
continue adding drops until pink coloration persists as shown by spot testing
on filter paper. Add one drop of concentrated sulfuric acid and resume adding
potassium manganate (VII) drop by drop. No decolorization occurs with tertiary
alcohols. The colour eventually fades with secondary alcohols, but persists
with primary alcohols.
16.1.3.1.2 Prepare sodium ethoxide
Sodium ethoxide is the salt of a weak acid, ethanoic acid, and a strong
base, sodium hydroxide.
Add a pinhead size piece of sodium to 1 mL of ethyl alcohol. Tests for
hydrogen gas:
Na (s) + 2C2H5OH (l) --> 2C2H5ONa
(s) + H2 (g)
sodium + ethanol --> sodium ethoxide + hydrogen
Evaporate the sodium ethoxide solution to form white crystals. Add drops
of water and tests for litmus that turns blue.
16.1.3.2 Phenols See diagram 16.1.4.3: Phenols, quinones,
naphthols, coniferyl alcohol (p-coumaryl alcohol), urushiol, organohalogens See diagram 16.1.4.4: Phenols, quinones See 19.2.1.6: Antioxidant phenols,
antioxidants, vitamin E, beta-carotene See 19.2.1.7: Cholesterol
1. Phenols, Ar-OH, are compounds with an hydroxyl group, -OH, firmly attached
to an aromatic ring, e.g. benzene, 2-naphthol, benzene-OH, hydroxybenzenes
Phenols (hydroxyl group -OH), connected to a carbon atom in a benzene
ring, benzene-OH, hydroxybenzenes
The -OH is so firmly attached that the O-H bond tends to break to lose
an H+ ion to form a weak acid.
2. Phenols divided into mono-, di-, tri- tetra-, and polyhydric phenols.
e.g. p-chlorophenol, C6H4ClOH, 2, 4, 6-tribromophenol,
C6H2Br3OH 16.1.3.2a Pyrogallol, C6H3(OH)3,
1,2,3-trihydroxybenzene, white crystals, reducing agent, alkaline solution,
(use sodium hydrogen carbonate not sodium hydroxide), reacts with oxygen
in the air to form a brown polymer. Pyrogallol is used in experiments where
oxygen must be eliminated from a gas or from the air. Pyrogallol is prepared
by heating gallic acid, C6H2(OH)3COOH,
(3,4,5-trihydroxybenzoic acid). 16.1.3.2.1 Carbolic acid,
phenol
Benzene compounds: See diagram 16.8.1
1. Carbolic acid, C6H5OH, "phenol" from coal tar
fraction 170oC to 230oC, colourless hygroscopic crystals.
Phenol is acidic so ionizes in water:
C6H5OH --> H+ + C6H5O- Do not wash off with alcohol because carcinogenic products or explosive
materials may form. To avoid carcinogenic byproducts, use sulfuric acid,
not hydrochloric acid, as a catalyst to prepare polymers.
2. "Phenol", carbolic acid (C6H5OH), is a pale pink
crystalline solid, solid because of the hydrogen bonds between the phenol
molecules. Pure phenol (carbolic acid) blisters the skin but it is still
used in carbolic soaps as an antiseptic. Formerly, it was used as an antiseptic
spray in early medical operations. Other antiseptics and disinfectants include
TCP (2.4.6-trichlorophenol), and Dettol
(4-chloro-3,5-dimethylphenol).
Phenol as a weak acid: phenol + H2O <=> H3O+
+ phenoxide ion-
Phenol reacts with alkalis: phenol + NaOH (aq) <=> sodium phenoxide
(aq) + H2O (l)
Halogenation of phenol: phenol + bromine --> 2.4.6-tribromophenol,phenol
+ chlorine --> chlorophenol
carvacrol, cymophenol, C6H3CH3(OH)(C3H7), monoterpenoid phenol, in oregano 16.1.3.2.2 Naphthols See diagram 16.1.4.3: Phenols, Quinones,
naphthols | See 12.11.5.7: Tests for
carbonates, Molisch's test (α-naphthol test)
1-naphthol, C10H7OH, a-naphthol, α-naphthol, naphthalen-1-ol,
tests for carbonates
2-naphthol, C10H7OH, b-naphthol, beta-naphthol,
naphthalen-2-ol, white solid, antioxidant in rubber products, antiseptic,
tests for primary amines 16.1.3.2.3 Cresols
Cresols, monomethylphenols, epoxy compounds, e.g. 1, 2-epoxypropane,
catechol [C6H4(OH)2],
pyrocatechol, 1,
2-dihydroxybenzene, 2-hydroxy phenol, urushiol (C6H4(OH)2). 16.1.3.2.4 Resorcinol See diagram 16.1.4.2: Resorcinol
Resorcinol, 1,3-dihydroxybenzene, benzene-1-3-diol, C6H4(OH)2,
dihydroxy phenol, colourless crystals, used for cold-setting adhesives
with formaldehyde
16.1.3.2.5 Triclosan,
organohalogens See diagram 16.1.4.2: Triclosan
Triclosan, 5-chloro-2-(2,4-dichlorophenoxy) phenol, C12H7Cl3O2,
is an organohalogen polychlorophenoxy phenol used in anti-bacterial and
anti-fungal products, and in low concentrations in many other products,
including toothpaste, mouthwash, deodorants, soap, scent, detergent dishwashing
liquid, at high concentrations is Harmful by inhalation, irritant, environmental
danger, and is suspected of causing bacterial resistance because of it
widespread use and occurrence in the environment and may weaken the immune
system. Other organohalogens include: 2, 4, 6-trichlorophenol, 2, 4, 6-tribromianisole,
2, 4, 6-trichloroanisole, chlorophenol compounds + filamentous fungi -->
2, 4, 6-trichloroanisole 16.1.3.3 Thiols See diagram 16.1.4.3: Thiophenol (phenyl
mercaptan), | See diagram 16.13.10: Metam,
zineb
Thiols, thio-alcohols (RSH, R not equal to H), (sulfhydryl group: -SH,
characteristic of thiols),
(Suffix: -thiol), [old name: mercaptans, because
react with mercuric ion to produce mercaptides (RS)2Hg], e.g.
methanethiol, methyl mercaptan (CH3SH), ethanethiol (MeCH2SH),
ethyl mercaptan (ethanethiol or ethan-ethiol or captan), (C2H5SH),
1-butanethiol, n-butyl-mercaptan (CH3CH2CH2CH2SH),
thiophenol, phenyl mercaptan Ph-SH, sodium thiolate: (RS-Na+),
thiols, RS-H, are oxidized to disulfides, RS-SR
Methanethiol from asparagus
The methylmethionine and asparagusic acid, α-aminodimethyl-γ-butyrothetin,
in asparagus may produce methanethiol, dimethyl disulfide and dimethyl
sulfone in people who eat asparagus. However, less than 50% of adults can
smell these compounds in the urine. 16.1.3.4 Ethers
Two hydrocarbon groups linked by one oxygen, compounds in the form: R1OR2
(R not equal to H), where R1 may or may not be the same as R2, e.g. the
anaesthetic diethyl ether. Ethers (ROR'), (CnH2n+2O),
alkyl ethers, ethoxethane ether, e.g. dimethyl ether (CH3OCH3),
diethyl ether, ether anaesthetic (C2H5OC2H5,
CH3CH2OCH2CH3). 16.1.3.6 Acetates (ethanoates), ROAc, salt or ester
of ethanoic acid (acetic acid)
As a salt: sodium acetate, sodium ethanoate (CH3COONa). As an
ester: ethyl ethanoate (CH3COOC2H5)
16.1.3.7 Benzoyl group, benzene carbonyl group
C6H5CO-
e.g. benzoyl chloride (C6H5COCl) 16.1.3.8 Acetals (alcohol + aldehyde), RCH(OR')2
Acetal, 1,1-diethoxy ethane [CH3CH(OC2H5)2],
smelly liquid, formed by reaction of acetaldehyde with ethanol
Hemiacetals: [RCH(OH)R'], Di-methyl acetals: [RC(OMe)2R'],
Di-ethyl acetals: [RC(OEt)2R'] (polyacetals, polyoxymethylene resin POM) 16.1.5.3 Salts, e.g. sodium
ethanoate (sodium acetate) (CH3COONa), ammonium acetate (CH3COONH4)
NaHCO3 + CH3COOH --> CH3COONa + H2O
+ CO2 (g) 16.1.5.5 Acyl halide, acid chloride, Acid chlorides
group: (-COCL), Suffix: -oyl chloride
acyl chloride (RCOCl), e.g. ethanoyl chloride (acetyl chloride), (CH3COCl) 16.1.5.6 Amides, acid amides (-amide), (amide group:
-CONH2, RCONH2) Carbamates
e.g. urea (H2NC=ONH2), [IUPAC: Do NOT distinguish
amides with NH2, NHR, NR2 groups by the terms "primary,
secondary, tertiary".]
(primary amides RCONH2), e.g. alkanamides: ethanamide (acetamide),
(CH3CONH2) propanamide (C2H5CONH2)
(secondary amides, N-substituted amides RCONHR')
(tertiary amides RCNR'R"), secondary or tertiary amides have the prefix
N, e.g. N-ethylethanamide CH3CONHCH2CH3,
N.N-dimethylmethanamide HCON(CH3)2 (the polymer group
-CO-NH-), (inorganic amides, e.g. KNH2) 16.1.5.6.01 Physostigmine
From Calabar bean, (Physostigma venenosum), alkaloid C15H21N3O2,
poison bean but used in pharmacy as ant-CNS depression, antidote for belladonna
poisoning, cholinesterase inhibitor 16.1.5.6.1 Acrylamide,
2-Propenamide, ethylene carboxamide, acrylic amide, vinyl amide, Toxic
if ingested:
Acrylamide, CH2CHCONH2, is the amide of acrylic
acid, propenoic acid, (CH2CHCOOH), an unsaturated liquid carboxylic
acid. It is a poison, harmful if swallowed, inhaled or absorbed through
skin, affects central and peripheral nervous systems and reproductive system,
causes irritation to skin, eyes and respiratory tract, suspected cancer
hazard depending on level and duration of exposure, possible birth defect
hazard, thermally unstable, can polymerize explosively if heated to the melting
point, most common
in overcooked french fries and potato chips, also burned
toast and burned high carbohydrate foods. 16.1.5.7 Acid anhydrides, acyl anhydrides, anhydrides
[RCO-O-COR' (R(C=O)O(C=O)R')]
e.g. ethanoic anhydride (acetic anhydride), [(CH3CO)2O],
ethanoic anhydride [CH3(C=O)O(C=O)CH3],
trifluoroethanoic
propanoic anhydride [CH3CH2(C=O)O(C=O)CF3]
16.1.5.8 Imides (R1CO-NH-COR2), (imido group: -CONHCO-),
e.g. glutemide (C13H15NO2),
the polymer
group (-CO-NR-CO), polyimides, N-(trichloromethylthio), cyclohex-4-ene-1,
2-dicarboyimide 16.1.12 Fractional distillation
of crude oil
A fractionating column is used to separate the distillates that boil within
a temperature range, i.e. the fractions. Fractional distillation of crude
oil: petroleum gas (LPG), naphtha, petrol (gasoline), kerosene (paraffin
oil), diesel oil, lubricating oil (motor oil), paraffin wax (fuel oil), residuals
(bitumen, "tar", asphalt, waxes).The word "asphalt" can refer to natural
bituminous pitch, e.g. the Trinidad Pitch Lake, or the fraction of crude
oil produced by distillation or the "hot mix" mixture of aggregate and bitumen
used to surface roads, paths and school playgrounds. 16.1.12.1 Petroleum
gas (methane, ethane, propane, butane)
Mix of 1 to 4 carbon atoms, boiling range < 40oC. Liquefied
under pressure as LPG (liquefied petroleum gas), a mixture mainly of propane
(C3H8), and butane (C4H10). 16.1.12.2 Naphtha
(petroleum naphtha, ligroin), processed to make gasoline
Mix of 5 to 9 carbon atoms, mainly aliphatic, e.g. alkanes, boiling range
120oC to 180oC, or < 200oC. The light
hydrocarbon cut between gasoline and kerosene. (Another naphtha can also
be produced from coal tar.) 16.1.12.3 Petrol,
"gas", gasoline, motor fuel
Mix of C6H14 to C11H24, 5 to
12 carbon atoms, alkanes and cycloalkanes, boiling range 40 to 205oC 16.1.12.4 Kerosene,
kerosine, paraffin oil, jet engine fuel, tractor fuel
Mix of C12H26 to C15H32,
10 to 18 carbon atoms, alkanes and aromatics, boiling range 175oC
to 325oC 16.1.12.5 Diesel
oil, gas oil or diesel distillate, diesel fuel, heating oil
Mix of C15H32 to C18H38,
12 or more carbon atoms, alkanes, boiling range 250oC to 350oC 16.1.12.6 Lubricating
oil, motor oil, grease
Mix of C16H34 to C24H50, 20
to 50 carbon atoms, alkanes and cycloalkanes and aromatics, boiling range
300oC to 370oC 16.1.12.7 Paraffin
wax, heavy gas, fuel oil, Mix of C20H42 and higher
hydrocarbons, 20 to 70 carbon atoms, alkanes and cycloalkanes and aromatics,
boiling range 370oC to 600oC 16.1.12.8 Residuals,
bitumen, "tar", asphalt, waxes
A mix of C24H50 and higher hydrocarbons, multiple-ringed
compounds, 70 or more carbon atoms, boiling range > 600oC
Petroleum jelly is a saturated semi-solid of crystalline
and liquid hydrocarbons, carbon numbers < C25, made by dewaxing paraffinic
residual oil. (naphtha, "Greek fire", was an inflammable bituminous substance used in
warfare.) 16.1.13 Prepare triodomethane (iodoform) See 1.6: Iodine solution | See diagram 16.2.2: Halogen compounds, haloalkanes
Add five drops of iodine solution to five drops of ethanol. Add drops
of dilute sodium hydroxide solution until the brown colour of iodine disappears.
Observe the crystals under a microscope.
C2H5OH + 4I2 + 6NaOH --> HCOONa + 5NaI
+ 5H2O + CHI3
ethanol + iodine + sodium hydroxide --> sodium methanoate (sodium formate)
+ sodium iodide + water + triodomethane (iodoform)
16.1.14 Prepare trichloromethane (chloroform) See diagram 16.1.7: Prepare chloroform | See 16.2.2: Chlorinated hydrocarbons, haloalkanes
Bleaching powder is usually a mixture of calcium chlorate (I) [basic calcium
chloride, calcium hypochlorite], calcium chloride and calcium hydroxide
prepared by passing chlorine gas through a calcium hydroxide solution. Calcium
chlorate (I) oxidizes ethanol to ethyl aldehyde. Aldehydes or ketones have
a hydrogen atom attached to the carbon atom attached to the carbonyl group,
C=O.
This hydrogen atom can be replaced by a halogen atom to form halogen compounds.
If a molecule contains three such hydrogen atoms, e.g. ethanol and propanone
(acetone) molecule, a trihalide may be formed, e.g. trichloromethane (chloroform,
CCl3).
H3C-C(O)-R + 3OX --> X3C-C(O)-R
ketone or aldehyde hypochlorite --> trihalide
The trihalide decomposes in a basic solution to a haloform (CHX3),
e.g.:
CHCl3C-C(O)-R (l) + OH- (aq) --> CHCl3
(l) + RCOO- (aq)
16.1.14.1 Reaction of acetone with bleaching powder
CH3COCH3 + 3Cl2 --> CCl3COCH3
+ 3HCl
2CCl3COCH3 + Ca(OH)2 --> 2CHCl3
+ (CH3COO)2Ca
Ca(OH)2 + 2HCl --> CaCl2 + 2H2O
16.1.14.2 Reaction of ethyl alcohol with bleaching powder
C2H5OH (l) + Cl2 (g) --> CH3CHO
(l) + 2HCl (aq)
ethyl alcohol + chlorine --> ethyl aldehyde
CH3CHO (l) + 3Cl2 (g) --> CCl3CHO
(l) + 3HCl (aq)
2CCl3CHO (l) + Ca(OH)2 (aq) --> 2CHCl3
(l) + (HCOO)2Ca (aq)
Be careful! Do not allow any flames in the laboratory!
Grind together in a mortar and pestle 5 g bleaching powder and 10 mL water.
Put the mixture into the test-tube of the gas preparation apparatus. Cool
the test-tube. Add either 4 mL ethanol in 2 mL water or 4 mL propanone (acetone)
in 2 mL of water. Swirl the contents of the test-tube and keep it cool. Use
an electric water bath to warm the temperature to 55oC. Water
and trichloromethane condense in the receiving test-tube leaving a calcium
salt solution in the test-tube. Add water to the distillate and separate
the trichloromethane with a separating funnel. 16.2.2 Halogen compounds, haloalkanes (alkyl halides),
halogen derivatives
Acyl halides, (acid halides; RCOX, where X = halide group and R = organic
group, e.g. acetyl = CH3CO-)
Haloforms, e.g. trihalomethanes CHX3 Alkanes react with chlorine and bromine in ultraviolet light to produce
haloalkanes, e.g. 2-chloropropane. See diagram 16.2.2: Chlorinated hydrocarbons,
methyl chloride, methylene chloride, chloroform, carbon tetrachloride See diagram: 16.13.5: Bifenox, dicofol, naled,
trichlorophon, tetrachlorvinphos See diagram 16.13.11: MCPA, 2, 4-D, 2, 4,
5-T, picloram
1.0 Chlorine: acyl chlorides,
acid chlorides (acyl = RC=O-), ethanoyls (-COCl), (-oyl chloride), ethanoyl
chloride (acetyl chloride), (CH3COCl), chloroform CHCl3,
chloromethane (methyl chloride), (CH3Cl), ethylene dichloride
(1,2-dichloroethane, Freon 150), (ClH2C-CH2Cl), chloroethene
(vinyl chloride) (CH2:CHCl), tetrachloromethane (carbon tetrachloride),
(CCl4), phosgene (carbonyl dichloride), COCl2, chlorine
+ sulfur: thiophosgene (thiocarbonyl dichloride), (CSCl2), chlorine
+ OH: dicofol, MCPA, 2, 4-D, 2, 4, 5-T, chlorine + N: Bifenox, chlorine
+ P: trichlorophon, tetrachlorvinphos
2.0 Iodine: iodoform (tri-iodomethane),
(CHI3), iodoethane (CH3CH2I)
3.0 Bromine: bromoform (CHBr3),
ethyl bromide (bromoethane), (C2H5Br), ethylene dibromide
(1:2-dibromoethane), Halons (fire extinguishers): Halon-1211 bromochlorodifluoromethane
(CBrClF2), Halon-1301 bromotrifluoromethane (CBrF3)
4.0 Fluorine: fluoroform (CHF3),
tetrafluoroethene (CF2CF2), polytetrafluoroethene
(PTFE, Teflon), (-[CF2-CF2]x-)
5.0 Magnesium with PTFE, polytetrafluoroethylene,
aircraft flares, heat-seeking missile decoys
2n Mg + (C2F4)n --> 2n MgF2(s) + 2n
C(s)
6.0 Chlorofluorocarbons, CFCs
(old name = Freons): CFC-11 trichlorofluoromethane (CCl3F),
CFC-12 dichlorodifluoromethane (CCl2F2)
See "Freons": 12.19.5.1 16.2.3 Organometal compounds (prefixing the metal
with organo-), e.g. organomagnesium compounds,
MeMgI iodo(methyl)magnesium,
Et2Mg diethylmagnesium
16.2.3.1 Carbides (C4-), (carbon +
metal), e.g. chromium carbide, Cr3C2, iron carbide
Fe3C (cementite), silicon carbide SiC, calcium dicarbide, (calcium
carbide, carbide, calcium acetylide, ethnide), (CaC2), tungsten
carbide ("carbide", WC)
Methanides + water --> methane, e.g. aluminium carbide, (Al4C3)
Acetylides (percarbides, C22-) + water --> acetylene,
e.g. Na2C2, CaC2
Sesquicarbides, e.g. Mg2C3
Iron carbide is formed with carbon monoxide when iron oxide is heated
with charcoal.
3Fe2O3 +11C --> 2Fe3C + 9CO (g) 16.2.4 Nitrogen compounds, one atom of nitrogen See 16.1.5.6: Amides 16.2.4.2 Nitriles (acid nitriles, alkyl cyanides,
cyanides), (-CN, RC≡N), (cyanide ion: CN-), e.g. ethane nitrile
(methyl cyanide, ascetonitrile) (CH3C≡N), 5-methoxyhexanenitrile,
[CH3C(OCH3)HCH2CH2CH2C≡N],
acrylonitrile for making Orlon (vinyl cyanide, 1-cyanoethene), (CH2=CH-C≡N) 16.2.4.2.1 Cyanamides, (inorganic, CN22-),
ionization reaction of methylamine See diagram 16.2.4.2.1: Melamine
cyanic acid (fulminic acid), (HOCC≡N), (cyanates, fulminates), Isocyanic
acid (H-N=C=O), isocyanates
(isocyanate group: -NCO, HN=C=O), isocyanides
(HN≡C), hydrocyanic acid (HC≡N)
CaCn2 + H2O + CO2 --> H2NCN
+ CaCO3
calcium cyanamide + water + carbon dioxide --> cyanamide + calcium
carbonate
(NH2)2CO --> HCNO + NH3
urea --> cyanic acid + ammonia
6HCNO --> C3H6N6 + 3CO2
(polymerization reaction)
cyanic acid --> melamine + carbon dioxide
6(NH2)CO --> C3H6N6 + 6NH3
+ 3CO2
Melamine, 1, 3, 5-triazine-2, 4, 6-triamine, is 66% nitrogen w/w and is
used in the plastics industry. Unfortunately, its high nitrogen content
has been the reason for its use as a powdered milk pollutant in China resulting
in death and kidney problems in young babies due to the formation of kidney
stones.
Commercial
Melamine crockery, green, virtually unbreakable, dishwasher safe, Not
suitable for microwave oven, plate, 18 mm diameter 16.2.4.3 Amines, aliphatic amines (RNH2-,
R = alkyl group), ionization reaction of methylamine
Primary amines: RNH2, NH2- = amino group,
e.g. mono-methylamine methylamine (CH3NH2), ethylamine
(CH3CH2NH2)
Secondary amines: R2NH, NH = imino group, e.g. di-methylamine
didimethyl amine [(CH3)2NH], diethylamine
Tertiary amines: R3N, trimethylamine [(CH3)3N],
triethylamine, methylamine hydrochloride Ionization reaction of methylamine
CH3NH2 + H2O <--> CH3NH3+
+ OH- Nitrosamines, produced by nitrous acid with secondary amines, can
be formed in the gut when nitrites react with amino acids. Nitramine, (acid-base indicator,
3.5), C7H5N5O8, tetryl. colourless-yellow crystals, explosive formerly used in munitions 16.2.4.3.1 Ethylenediamine
ClCH2CH2Cl + 4 NH3 --> H2NCH2CH2NH2
+ 2 NH4Cl
1,2-dichloroethane + ammonia --> ethylenediamine + ammonium chloride 16.2.4.3a Imines
Imino group = ring containing (-NH-), or (=NH), linked to C], (RN=CR',
where R = H or hydrocarbyl, e.g. (ethyl-), 0-benzoquinonedimine
Imine primary RC(=NH)R’ (imino-), (-imine)
Imine secondary RCH=NR’ (imino-), (-imine) 16.2.4.4 Nitroalkanes (nitroparaffins),
(CnH2n+1NO2)
Nitromethane (CH3NO2), nitroethane, urea (carbamide) 16.2.4.5 Nitrites (NO2-),
dioxonitrate ion, salts or esters of nitrous acid (O=NOH), e.g. sodium
nitrite and potassium nitrite as meat curing agents 16.2.4.6 Oximes (hydrox-imino-alkanes)
Formula R1R2C=NOH, where R1= organic side chain and if R2 = hydrogen,
aldoxime forms or if R2 = organic group, ketoxime forms.
(-CNOH group), (ketone or aldehyde + hydroxylamine - water), (RCNOHR'),
e.g. ethanal oxime (acetaldehyde oxime, AAO), (CH3CH=NOH) 16.2.4.7 Cyanocrylates
[(CH2)C(CN)COOR]
e.g. "Superglue": Me or Et ester
16.2.5 Nitrogen compounds, two or more nitrogen atoms 16.2.5.1 Azide
Azide compounds: (N3-), or (-N3), (-N=N+N-),
usually attached to carbon, e.g. sodium azide (NaN3), phenyl
azide or azidobenzene (PhN3), diazine (diimide), (HN=NH), also,
salts of hydrazoic acid, HN3, e.g. sodium azide (NaN3).
16.2.5.2 Azo
Azo compounds: derivatives of diazene (diimide), HN=NH, with both hydrogens
substituted by hydrocarbyl groups, e.g. azobenzene or diphenyldiazene (PhN=NPh).
hydrazone (ketone + hydrazine (N2H4) - water), (RC=NNH2R')
16.2.5.3 Diazo
Diazo compounds: (RN=NR'), e.g. diazomethane (CH2=N2),
diazonium compounds [(RN≡N+) Cl-]
benzenediazonium chloride + phenol --> 4-(phenylazo)phenol + NaCl
benzene-N+≡NCl- + H-benzene-OH + NaOH --> benzene-N=N-Benzene-OH
+ NaCl + H2O
4-(phenylazo) phenol is a yellow dye
Azo dyes of the textile industry use diazonium salts. The material is first
soaked in a soluble salt of phenol or naphthol then soaked in a diazonium
salt so that the dye forms in the cloth. 16.2.5.4 Phenylhydrozone
Phenylhydrozone [RC=N(NH), (Phenyl group) R'], (ketone or aldehyde + phenylhydrazine,
[C6H5(NH)NH2] - water),
2, 4-dinitrophenylhydrozone,
semicarbazone [RC=N(NH)CO(NH2)R']
16.2.6 Phosphorous compounds, organophosphorus insecticides
Organophosphorus insecticides (mostly thiophosphates), TEPP (tetraethylpyrophosphate,
no longer used as insecticide), parathion, maldison (Malathion), dimethoate
(Rogor), dichlorvos (dimethyl dichlorovinyl phosphate, DDVP, Shelltox strips),
demetron (Systox),
Organophosphates, acephate, dichlorvos, dimethoate, malathion (maldison),
parathion See diagram 16.13.6: Benomyl, captan, glyphosate,
paraquat
1. Phosphonic acid, orthophosphorous acid [HP(=O)(OH2) H3PO3]
2. Phosphonoglycine, N-(phosphonomethyl) glycine, glyphosate (in "Roundup"
weedicide), (C3H8NO5P)
3. Organic phosphates: acephate, diazinon, dichlorvos, dimethoate, malathion
(maldison) naled, parathion
16.2.8 Sulfur compounds, For the "thio" prefix,
replace oxygen by sulfur, e.g. thiobenzamide [PhC(=S)NH2] 16.2.8.1 Isothiocyanates
(old name: mustard oil), (RN=C=S), mustards [X(CH2.CH2)2S] 16.2.8.2 Sulfides: RSR
(R not equal to H), (old name: thioethers), e.g. diallyl sulfide (garlic
smell), [CH2=CHCH2)2S], or inorganic salts
of hydrogen sulfide. Most people who eat asparagus notice a smell, the over-boiled
cabbage smell, in their urine because of sulfur compounds, e.g. dimethyl
sulfide, dimethylsulfone, sulfimides (sulfilimines): (H2S=NH) 16.2.8.3 Sulfonic acids,
[HS(=O)2OH] 16.2.8.4 Sulfonium compounds:
R3S+, e.g. trimethylsulfonium chloride {[(CH3)3S]+Cl-}
16.2.8.5 Thiocyanates:
[RC(=O)SN] salts and esters of thiocyanic acid HSCN, e.g. methyl thiocyanate
(CH3SC≡N) 16.2.8.6 Silicones: polymeric
unbranched siloxanes, formula (-OSiR2-)n (R not
equal to H) 16.2.8.7 Siloxanes
Saturated silicon-oxygen hydrides with chains of alternating silicon and
oxygen atoms, e.g. unbranched [H3Si(OSiH2)nOSiH3],
branched [H3Si(OSiH2)nOSiH(OSiH2OSiH3)2].
"Volasil" is octamethylcyclotetrasiloxane. Dimethylpolysiloxane is an anti-caking
agent, emulsifier and anti-foaming agent.
16.2.8.8 Thiols, thio-alcohols
See 16.1.3.3 16.2.8.9 Sulfoxide, dimethyl
sulfoxide, (DMSO (CH3)2SO), (C2H6OS)
propanethial S-oxide, C3H6OS, lachrymatory factor
from cut onion cells, Allium cepa, formed when enzyme allinase reacts
wit S-1-propenyl-L-cysteine sulfoxide 16.2.10 Coal tar products, creosote
Chemicals produced from destructive distillation of coal when making coke
for steel production. Many organic compounds can be isolated by distillation
of coal tar but many are now made from petroleum or natural gas. The residue
of coal tar distillation is called pitch and is used for road tar and waterproofing
of roof material. The residue of petroleum distillation is called asphalt
but also called "tar". Coal tar paints resist heat and moisture. Coal tar
dyes, called azo dyes, are made from azobenzene and were used as food colourings.
Coal tar products include:
1. hydrocarbon oils, e.g. benzene, toluene, xylene
2. phenols, e.g. carbolic acid, and
3. bases. e.g. pyridine.
Coal tar is a creosol mixture that includes 2-hydroxytoluene, 3-hydroxytoluene,
4-hydroxytoluene. It sensitizes skin to sunlight, so use gloves because
it may cause skin cancer. It is used as a wood preservative of railway
sleepers, telegraph poles., fungicide, soap for treatment of skin diseases,
and sheep dip insecticide. However, wood creosote is a mixture of phenols of wood tar and is used
as a disinfectant, cough medicine, diarrhoea medicine, preservative, and
antiseptic. 16.3.1 Prepare ethanal (acetaldehyde)
with potassium dichromate
Add two drops of 0.1 M potassium dichromate solution to two drops of ethanol
and ten drops of dilute sulfuric acid. Heat gently. The orange potassium
dichromate solution turns green showing the presence of Cr3+.
The reaction forms ethanal then ethanoic acid (acetic acid). Note the odour
of an acetaldehyde.
C2H5OH + (O) --> CH3CHO + H2O
ethanol + (oxygen) --> ethanal + water
CH3CHO + (O) --> CH3COOH
ethanal + (oxygen) --> ethanoic acid
K2Cr2O7 + 4H2SO4 +
3CH3CH2OH --> K2SO4 + Cr2(SO4)3
+ 7H2O + 3CH3CHO 16.3.1a Aldehydes, alkanals (aliphatic aldehydes),
ketones, quinones
Aldehydes (-CHO), (-al) alkanals, e.g. methanal (formaldehyde), (CH2=O,
HCHO), ethanal (acetaldehyde), (CH3CHO)
Aldehydes are compounds in the form RC(=O)H, where a carbonyl group is
bonded to one hydrogen atom and to one R group. Aldehydes contain the aldehyde
group (-CHO), which is a carbonyl group (C=O), with a hydrogen atom attached
to the carbon atom. Methanal (HCOH, formaldehyde), and ethanal (CH3CHO,
acetaldehyde), are the simplest aldehydes (RCHO, alkanals). Aldehyde names
end with "-al". Aldehydes are reducing agents and can be detected with Tollens'
test or Fehling's test. Most
monosaccharides and disaccharides can act as
reducing agents, but not sucrose, and can be detected by Fehling's test
or Benedict's test.
16.3.5.1 Aesculin (escalin)
It is a glucoside from the horse chestnut Aesculus hippocastanum.
It is used to identify Enterococcus bacteria. It gives pale blue
colour by reflected light and straw colour by transmitted light. 16.3.5.2 Amido phthalic
acid and amido-tarephthalic acid
It gives pale violet colour by reflected light and pale yellow colour
by transmitted light. Amido-tarephthalic acid gives bright green colour
by reflected light and pale green colour by transmitted
light. 16.3.5.3 Eosin (eosine)
Eosin, bromoeosin, gives yellow green colour by reflected light and orange
colour by transmitted light. It is formed by reaction of bromine with fluorescein,
the potassium salt of tetrabromo-fluorescein, sodium-2,4,5,7-tetrabromofluorescein,
C20H6Br4O5K2. “Eosin
Y” has yellowish colour, and “eosin B” (Acid red), has bluish colour. It
is used as a counter stain to haematoxylin for microscopic examination.
Eosin, an acidic dye, stains cytoplasm stained orange-pink and haematoxylin,
a basic dye, stains nuclei
blue or purple where nucleic acids mainly occur.
Eosin stains red blood cells intensely red. 16.3.5.4 Fluorescein See diagram 16.3.1.1: Fluorescein
It gives intense green colour by reflected light and orange yellow colour
by transmitted light. It is 1, 3-dihydoxybenzene phthalein, [2-(6-hydroxy-3-oxo-xanthen-9-yl),
benzoic acid], C20H12O5, red crystals
that can dissolve in alkali to form a red colour and green fluorescence. 16.3.5.5 Fraxin
It gives blue-green colour by reflected light and pale green colour by
transmitted light. It is a colourless glucoside found in the bark of the
ash tree, Fraxinus. Fraxin and esculin are two coumarins found in
Actinidia chinensis and Actinidia deliciosa (kiwi fruit, Chinese
gooseberries). 16.3.5.6 Magdala red
It gives opaque scarlet colour by reflected light and brilliant carmine
colour by transmitted light. 16.3.5.7 Quinine
Quinine, C20H25N2O2, gives
a pale blue colour by reflected light and no colour by transmitted light.
It is an alkaloid from the bark of Cinchona and Remijia in
South America. It was formerly an anti-malarial medicine and is still used
for treatment of some heart conditions. As a medicine it was taken in carbonated
mineral water but nowadays is still taken as a beverage called "tonic water"
which is valued for its slightly bitter taste. Tonic water is not a medicine.
Fluorescence spectroscopy can be used to determine the
percentage quinine
content in commercial samples of tonic water or bitter lemon. by comparing
the fluorescence of a sample in ultraviolet light to the fluorescence of
a standard quinine sulfate solution containing 10 mg of quinine sulfate
in 1L of deionized water.
Large doses of quinine used to treat malaria infection may cause heart
problems but small doses, e.g. in a small bottle of tonic water, have
been effective in treating leg muscle cramps. 16.3.5.8 Safranin (safranine,
safranin O, basic red 2)
It gives yellow red colour by reflected light and crimson colour by transmitted
light. It is a biological stain colouring all cell nuclei red. It is used
as a counterstain in a Gram stain in microbiology. It can also be used for
the detection of cartilage and mucin and as a redox indicator in analytical
chemistry. Safranines are the azonium compounds of symmetrical 2, 8-dimethyl-3,
7-diamino-phenazine. 16.3.2 Prepare ethanal with potassium manganate
(VII) [potassium permanganate, Condy's crystals]
Add one drop of 1% potassium manganate (VII) to five drops of ethanol
and ten drops of dilute sulfuric acid. Heat gently. The purple colour disappears
as potassium manganate (VII) solution is reduced to manganese (II) sulfate.
Note the odour of an acetaldehyde.
CH3CH2OH + (O) --> CH3CHO + H2O
2KMnO4 + 3H2SO4 + 5CH3CH2OH
--> K2SO4 + 2MnSO4 + 8H2O
+ 5CH3CHO
16.3.3 Oxidation of methanol to methanal using a
platinum catalyst See diagram 16.3.3: Oxidation of methanol
Be careful! This experiment may be too dangerous for your school.
Test
the experiment in the science preparation room before demonstrating it
in the classroom. Do not let anyone look down into the flask if the experiment
appears not to be working!
Put 10 mL methanol in a flask and heat briefly with a Bunsen burner. Heat
a piece of platinum wire connected to a copper wire until it is red-hot.
Hook a copper / platinum wire inside the flask to start the reaction. You
can reheat the wire if the reaction does not start. The reaction continues
till all the MeOH is used up. To stop the reaction, remove the catalyst
platinum wire catalyst. Be careful!
The methanol is oxidized to methanal when the vapour reaches a certain
concentration accompanied by a loud "whoosh" sound as the vapour burn and
leaves the flask. The copper T-piece acts as a chimney allowing entry of
air when the vapour bums. The Pt wire changes from red-hot to silver.
CH3OH + ½ O2 --> CH2O + H2 (Pt
catalyst)
CH2O + O2 --> CO2 + H2O
(Pt catalyst) 16.3.8 Ketones
(=CO), (-one), e.g. propanone (acetone), (CH3C=OCH3)
Ketones have a carbonyl group (C=O), bonded to two carbon atoms in the
form R2C=O, but neither R may be H. Ketones contain the ketone
group (-CO-). It is a carbonyl group with two single bonds to other carbon
atoms. Propanone (acetone, CH3COCH3), and butanone
(CH3COC2H5, methyl ethyl ketone), are
the simplest saturated ketones (R1COR2). Ketone names end with "-one". Ketones
cannot be detected with Tollens' test or Fehling's test.
Muscone, C16H3O, methylcyclopentadecanone, is the
perfume fixative musk from musk deer but is now produced artificially. 16.3.9 Diacetyl, 2,3-butanedione
Diacetyl, CH3COCOCH3, is used in the popcorn industry
to give a butter or butterscotch flavour to popcorn sold in bags. However,
workers in the popcorn industry have reported medical problems with their
respiratory systems, particularly the lungs, leading to workers compensation.
If you heat bags of popcorn in a microwave oven similar problems may occur.
The popcorn industry is considering not using diacetyl in bagged products. 16.3.10.0 Quinones See diagram 16.1.4.3: Quinones See 16.3.5.0: Polycyclic aromatics
(Contains C=O group in unsaturated ring, C=O groups in an unsaturated ring, as 1,2-quinones and 1, 4-quinones,
(e.g. cyclohexandiene-1,4-dione), cyclic dione structure, conjugated diketones,
e.g. benzoquinone, by conversion of -CH= groups into -C(=O)- groups, "quinone":
cyclohexadiene-1,4-dione, 1, 4-benzoquinone is the simplest quinone, C6H4O2,
all are coloured, many are plant pigments, e.g. lawsone from Lawsonia inermis the orange dye henna,
and juglone from walnut shells, Juglans
regia, formed from oxidation of hydroquinone and in pecan nuts,
and are used in dyes, hydroquinone, 1,4-dihydroxybenzene, used in photography
developer, also coenzymes Q in animal and plant cells and plastoquinones
involved in photosynthesis, also vitamin K.
Juglone, C10H6O3,
is produced by some trees in the walnut family, e.g. black walnut, Persian
walnut, butternut, and pecan and is leached or released into the soil.
Juglone has fungicide and insecticide properties but it is toxic to many
plant species. 16.3.10.1 Pindone See 16.3.5.1: Pindone, sodium salt
Pindone, (ISO 1750), (2-pivaloylindan-1,3-dione), C14H13O3,
is an anticoagulant drug used to control rodents and rabbits, e.g. "Bunnybait"
is 0.5 g /kg sodium salt of pindone is used as an oat bait for rabbits,
C14H13NaO3.