School Science Lessons
Topic 16 Organic chemistry, hydrocarbons, food tests, biochemistry
Updated 2009-11-14
Please send comments to: J.Elfick@uq.edu.au
See: IUPAC,Nomenclature of Organic Chemistry (website)
See: IUPAC Gold Book (website)
See: Interesting websites
Table of contents
16.1.0 Organic chemistry
Preparing different compounds
16.1.01 Addition reactions
16.1.02 Substitution reactions
16.1.03 Oxidation reactions - loss of electrons
16.1.04 Reduction reactions - gain of electrons
3.32.0: Prepare gases with a gas generation apparatus
16.1.1 Acyclic hydrocarbons, alkanes, alkenes, alkynes
16.1.1b Ethane (C2H6) prepare ethane
16.1.3.0 Alcohols, phenols, thiols, ethers, epoxy compounds, acetates (ethanoates), benzoyls, acetals
16.1.5.3 Salts, organic salts, e.g. sodium ethanoate (sodium acetate), (CH3COONa), ammonium acetate (CH3COONH4)
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 Amides, acid amides group: (-CONH2, RCONH2), suffix: (-amide)
16.1.5.6.1 Acrylamide, 2-Propenamide, ethylene carboxamide, acrylic amide, vinyl amide
16.1.5.7 Acid anhydrides, acyl anhydrides, anhydrides [RCO-O-COR' (R(C=O)O(C=O)R')]
16.1.5.8 Imides, imido group: (-CONHCO-),(R1CO-NH-COR2)
16.2.2 Halogen compounds, haloalkanes (alkyl halides), halogen derivatives
16.2.3 Organometal compounds, prefixing the metal with: (organo-)
16.2.3.1 Carbides (C4-), (carbon + metal)
16.2.4 Nitrogen compounds, one atom of nitrogen
16.2.4.2 Nitriles (acid nitriles, alkyl cyanides, cyanides)(-CN, RC=-N), cyanide ion: (CN-)
16.2.4.2.1 Cyanamides, inorganic, (CN22-), ionization reaction of methylamine, cyanic acid, melamine
16.2.4.3 Amines, aliphatic amines (RNH2-), R = alkyl group, ionization reaction of methylamine
16.2.4.3.1 Ethylenediamine
16.2.4.3.2 Chloramines
16.2.4.3a Imines, imino group: (-NH-) in a ring, or (=NH)
16.2.4.4 Nitroalkanes (nitroparaffins), (CnH2n+1NO2)
16.2.4.5 Nitrites (NO2-), dioxonitrate ion, salts or esters of nitrous acid, (O=NOH), Nitrites group: (-C=N), suffix:(-nitrite)
16.2.4.6 Oximes (hydrox-imino-alkanes), group: (C:NOH)
16.2.4.7 Cyanocrylates [(CH2)C(CN)COOR], "Superglue"
16.2.5 Nitrogen compounds, two or more nitrogen atoms
16.2.6 Phosphorous compounds
16.2.8 Sulfur compounds
16.2.10 Coal tar products
16.3.1.0 Aldehydes, ketones, quinones,aldehydes group: (-CHO), suffix: (-al)
16.3.1.1 Carbohydrates
16.3.5.0 Fluorescent liquids
16.4.1 Test organic acids and alcohols
16.4.2 Prepare ethanoic acid (acetic acid), ionization reaction
16.4.3 Prepare ethanedioic acid-2-water (oxalic acid), ionization reaction
16.4.4 EDTA, ethylenediaminetetraacetic acid, C10H16N2O8
9.137 Tests for fats and oils
3.79 Make soap from fats
16.4.5 Tests for proportion of fats in foods
16.4.6 Test gases from burning hydrocarbons
16.4.7 Tests for saturated hydrocarbons, bromine water test
16.4.8 Tests for saturated hydrocarbons, alkaline potassium manganate (VII) solution
16.4.9 Tests for saturated hydrocarbons, acidified potassium manganate (VII) solution
16.5.1.0 Esters, derivatives of fatty acids (RCOOR'), esters group: (-COOR), suffix: (-oate)
16.6.1.1 Proteins, peptides, amino acids
16.1.1 Acyclic hydrocarbons, alkanes, alkenes, alkynes
16.1.1.1 Alkanes (CnH2n+2),paraffins
16.1.1.1a Cycloalkanes
16.1.1a Methane (CH4), prepare methane gas
16.1.1a.01 Prepare methane gas
16.1.1a.02 Tests for methane gas, burn methane
16.1.1a.1 Natural gas
16.1.1a.2 Methane with chlorine
3.41.4 Reduce copper oxide with methane, natural gas
16.1.1b Ethane (C2H6), prepare ethane
16.1.1c Propane (C3H8)
16.1.1cc LPG (liquefied petroleum gas, LP gas)
16.1.1d Butane (C4H10), prepare butane
16.1.1e Pentane (C5H12)
16.1.1f Hexane (C6H14)
16.1.1g Heptane (C7H16)
16.1.1h Octane (C8H18), octane number
16.1.1.2 Alkenes, (CnH2n), olefins
16.1.1.2.1 Prepare ethene, (ethylene), gas
16.1.1.2.2 Dienes, isoprene units
16.1.1.3 Alkynes, (CnH2n-2), acetylenes
16.1.1.3.1 Prepare ethyne, (acetylene)
16.1.3.0 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
16.1.3.1.1 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)
16.1.3.2.1 Carbolic acid
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
16.1.3.5 Epoxy compounds (O atoms in CCO ring)
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)
16.1.12 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, 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 called 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, dimethyyl sulfoxide, DMSO (CH3)2SO, C2H6OS
16.1.3.3 Thiols, thio-alcohols
16.3.1.0 Aldehydes, ketones, quinones, aldehydes group: (-CHO), suffix: (-al)
See: Metaldehyde
16.3.1a Aldehydes, alkanals (aliphatic aldehydes), ketones, quinones
16.3.1 Prepare ethanal (acetaldehyde), with potassium dichromate
16.3.2 Prepare ethanal with potassium manganate (VII) [potassium permanganate, Condy's crystals]
16.3.3 Oxidation of methanol to methanal using platinum catalyst
16.3.4 Oxidation of glucose with sodium hydroxide and methylene blue, blue bottle experiment
16.3.5 Silver mirror tests for aldehydes, Tollens' tests for acetaldehydes
16.3.6 Silver mirror tests for aldehydes, Tollens' tests for glucose
16.3.7 Fehling's tests for aldehydes in solution
16.3.8 Ketones, group: (>C=O), suffix: -one
16.3.9 Diacetyl, 2, 3-butanedione
16.3.10 Quinones, contains C=O group in unsaturated ring, e.g.cyclohexandiene-1, 4-dione
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)
16.1.0 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 bond or =-s bond.
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
Preparing different 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 + ˝ O2 --> CH2O + H2 (Pt catalyst) [Oxidation of methanol to methanal using a platinum catalyst]
alkanals --> alkanoic acids
secondary alkanols (alcohols), (CH3)2CHOH --> alkanones
16.1.04 Reduction reactions - gain of electrons
alkanals (aliphatic aldehydes) --> primary alkanols (alcohols), (-CH@@@2-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, alkyne
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.
Hydrocarbons may be:
1. saturated, i.e. have only single bonds, or unsaturated, i.e. contain multiple bonds, e.g. double bond, triple bond,
2. aliphatic (alkane), or aromatic (arenes, benzene). Crude oil is a mixture of hydrocarbons.
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.
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. Alkanes are usually associated with natural petroleum deposits and can be distilled from petroleum.
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.1 Natural gas
Natural gas consists of about 90% methane together with varying proportions of ethane, propane, butane, nitrogen and carbon dioxide. Methane is odourless but during manufacture a rotten egg rank smelling compound, usually a mercaptan, e.g. captan (ethane thiol or ethyl mercaptan) is added so that the presence of the gas can be easily detected. Incomplete combustion yields carbon monoxide. Natural gas should burn with a 90% blue flame. Check the colour of the flame in the pilot light. If the flame appears yellow, the gas is probably contaminated by condensates during manufacture so contact the gas distribution authority for advice. Similarly, see assistance if you find yellow condensate when you wipe the wall, or a shadow behind pictures on the wall, or a black smudge on the bottom of cooking pots. Be careful! Do not search for a gas leak with a lighted match or lighted tape! Use a soap solution.
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).
16.1.1b Ethane (C2H6), prepare ethane
Colourless and odourless gas which has properties similar to methane.
See diagram 3.32: Collect insoluble gases over water | See diagram 16.1.1: Ethane
(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 yields 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 rank smelling compound is added so that the presence of the gas can be easily detected. Incomplete combustion yields 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
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 diagram 16.1.1: Butane
(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
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 number: n-butane, propane, butene-1, cyclopentane, propylene, benzene, 0-xylene, toluene
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 a motor car engine.
A high octane rating of a fuel means that it has less tendency to preignite in a high compression engine. Preignition 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
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)
See 3.32.0: Prepare gases with a gas generation apparatus
1. Slowly add 10 mL of concentrated sulfuric acid to 5 mL of ethyl alcohol 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. 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.
3. 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. 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
Early bicycle lamps used this reaction. However, the calcium carbide used to decompose in moist air to produce the unpleasant odour of acetylene. This decomposition could be lessened by pouring petroleum over the calcium carbide to exclude air and moisture.
1. Put sand in a dry test-tube and add pieces 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
2. Tests for ethyne (acetylene): Light the gas in the test-tube with a glowing splint. The gas burns with a smoky flame.
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.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, (a primary alcohol)
2. Butan-2-ol, 2-butanol, sec-butanol, sec-butyl alcohol, (a secondary alcohol)
3. Isobutanol, isobutyl alcohol, 2-methylpropan-1-ol, IBA, 2-methyl-1-propanol
4. tert-Butanol, tert-butyl alcohol, 2-methylpropan-2-ol
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. propane-1, 2, 3, -triol, glycerol [HOCH2CH(OH)CH2OH]
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
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 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, 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, e.g. "phenol", carbolic acid (C6H5OH),
Phenols divided into mono-, di-, tri- tetra-, and polyhydric phenols.
p-chlorophenol (C6H4ClOH), 2, 4, 6-tribromophenol (C6H2Br3OH), p-nitrophenol.
16.1.3.2.1 Carbolic acid
Carbolic acid, C6H5OH, "phenol" from coal tar fraction 170oC to 230oC, colourless hygroscopic crystals, acidic so ionizes in water
C6H5OH --> H+ + C6H5O-
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 (alpha-naphthol test)
1-naphthol, C10H7OH, a-naphthol, alpha-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, deodorants, soap, scent, dishwashing liquid, at high concentrations is HARMFUL by inhalation, IRRITATING, ENVIRONMENTAL DANGER, and is suspected of causing bacterial resistance because of it widespread use and occurrence in the environment.
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 16.13.6.6: 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, alpha-aminodimethyl-gamma-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
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),
16.1.3.5 Epoxy compounds
Have an oxygen atom attached to two carbon atoms of a carbon chain or ring system, so are cyclic ethers, e.g. 1, 2-epoxypropane.
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, e.g. "acetal", 1, 1-diethoxy ethane [CH3CH(OC2H5)2], Hemiacetals: [RCH(OH)R'], Di-methyl acetals: [RC(OMe)2R'], Di-ethyl acetals: [RC(OEt)2R']
16.1.5.3 Salts, e.g. sodium ethanoate (sodium acetate), (CH3COONa), ammonium acetate (CH3COONH4)
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)
See diagram 16.13.4.7: Carbamates, carbaryl, methiocarb
See diagram 16.13.8.0: Deet, DMP dimethylphthalate
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)
carbamates: esters of carbamic acid [H2NC(=O)OH], methiocarb, urethanes [R2NC(=O)OR', where R' not = H, R= ethyl], e.g. polyurethane resins, cyanides, imidesisocyanates, quinines, carbamide (urea), [CO(NH2)2], carbazole C12H9N, Deet
16.1.5.6.1 Acrylamide, 2-Propenamide, ethylene carboxamide, acrylic amide, vinyl amide
CH2CHCONH2, 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 kerosine. (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 5.4.8: 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)
Reactions 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)
Decomposes trichloromethane to calcium formate
Ca(OH)2 (aq) + 2HCl (aq) --> CaCl2 (aq) + 2H2O (l)
Reactions of acetone with bleaching powder
CH3COCH3 + 3Cl2 --> CCl3COCH3+ 3HCl
2CCl3COCH3 + Ca(OH)2 --> 2CHCl3+ (CH3COO)2Ca
Ca(OH)2 + 2HCl --> CaCl2 + 2H2O
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
See diagram 16.2.2: Methyl chloride, methylene chloride, chloroform, carbon tetrachloride
See diagram: 16.13.5.0: Bifenox, dicofol, naled, trichlorophon, tetrachlorvinphos
See diagram 16.13.7.7: MCPA, 2, 4-D, 2, 4, 5-T, picloram
Acyl halides, acid halides (RCOX, RCO. halogen atom, R = organic group), (acetyl = CH3CO-), Haloforms: trihalomethanes CHX3, Alkanes react with chlorine and bromine (halogens), in ultraviolet light to give haloalkanes, e.g. 2-chloropropane.
1. 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. Iodine: iodoform (tri-iodomethane), (CHI3), iodoethane (CH3CH2I)
3. Bromine: bromoform (CHBr3), ethyl bromide (bromoethane), (C2H5Br), ethylene dibromide (1:2-dibromoethane), Halons (fire extinguishers): Halon-1211 bromochlorodifluoromethane (CBrClF2), Halon-1301 bromotrifluoromethane (CBrF3)
4. Fluorine: fluoroform (CHF3), tetrafluoroethene (CF2CF2), polytetrafluoroethene (PTFE, Teflon), (-[CF2-CF2]x-)
Chlorofluorocarbons, CFCs (old name = Freons): CFC-11 trichlorofluoromethane (CCl3F), CFC-12 dichlorodifluoromethane (CCl2F2)
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. aluminium carbide (Al4C3), chromium carbide Cr3C2, iron carbide Fe3C (cementite), silicon carbide SiC, also dicarbides (C22-), e.g. calcium dicarbide (calcium carbide, carbide, calcium acetylide, ethnide), (CaC2)
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), (HOC =-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 dioxiode
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.
16.2.4.3 Amines, aliphatic amines (RNH2-, R = alkyl group), ionization reaction of methylamine
Primary amines: RNH2, NH2-= amino group, e.g. methylamine (CH3NH2), ethylamine (CH3CH2NH2)
Secondary amines: R2NH, NH = imino group, e.g. dimethyl 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.
16.2.4.3.1 Ethylenediamine
ClCH2CH2Cl + 4 NH3 --> H2NCH2CH2NH2+ 2 NH4Cl
1,2-dichloroethane + ammonia --> ethylenediamine + ammonium chloride
16.2.4.3.2 Chloramines
See also 18.7.21.4: Chloramines in swimming pools
Chloramine, NH2Cl
Dichloramine, NHCl2
Trichloramine, NCl3
Organic chororamines, RNHCl, are quite stable and useful sources of chlorine for bleaching, disinfection and oxidation when necessary to kill bacteria. However, chloramine can be eliminated from pool water only by using activated carbon filters
In pure form an oily liquid that is highly reactive and explosive. Some chemists who first discovered it or first used it were badly injured. It may be formed in swimming pools when disinfecting chloramine reacts with urea from swimmers' urine to irritate mucous membranes.
4NH3 +3Cl2 --> NCl3 + 3NH4Cl
ammonia + chlorine --> trichloramine + ammonium chloride
In hot water ammonia forms
NCl3 + H2O --> NH3 + 3HOCl
trichloramine + hot water --> ammonia + hypochlorous acid (chloric (I) acid)
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)
(-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
1. 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).
2. 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')
3. Diazo compounds: (RN=NR'), e.g. diazomethane (CH2=N2), diazonium compounds [(RN =- N+) Cl-]
4. 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
Organophosphates, acephate, dichlorvos, dimethoate, malathion (maldison), parathion
See diagram 16.13.6.1: 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, dimethyyl sulfoxide, (DMSO (CH3)2SO), (C2H6OS)
16.2.10 Coal tar products
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 products include:
1. hydrocarbon oils, e.g. benzene, toluene, xylene, 2. phenols, e.g. carbolic acid, and
3. bases. e.g. pyridine.
Coal tar paints resist heat and moisture. Coal tar wood preservatives, e.g. creosote, are use for soap, sheep dip, railway sleepers, telegraph poles. Coal tar dyes, called azo dyes, are made from azobenzene and were used as food colourings
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 counterstain to haematoxylin for microscopic examination. Eosin, an acidic dye, stains cytoplasm stained pink-orange and hematoxylin, 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 16.3.1.1.2.1: 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 goosberries).
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 color by transmitted light. It is an alkaloid from the bark of Cinchona and Remijia in South America. It was formerly an antimalarial 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 fluorescece of a sample in ultraviolet light to the fluorescence of a standard quinine sulfate solution containing 10mg of quinine sulfate in 1L of deionized water.
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 + ˝ O2 --> CH2O + H2 (Pt catalyst)
CH2O + O2 --> CO2 + H2O (Pt catalyst)
16.3.4 Oxidation of glucose with sodium hydroxide and methylene blue, blue bottle experiment
In a sodium hydroxide solution, the aldehyde glucose is oxidized by oxygen gas (dioxygen), to gluconic acid (d-gluconic acid, CH2OH(CHOH)4COOH), and then forms sodium gluconate. Methylene blue acts as an oxygen transfer catalyst and is reduced to colourless leucomethylene blue. Leucomethylene blue is then oxidized by oxygen in the air to methylene blue again. Methylene blue is a thiazine dyestuff, C16H18ClN3S, 3, 7-bis-(dimethylamino)-phenothiazin-5-ium chloride. Methylene blue is blue when oxidized and colourless when reduced
1. Solution 1: Add 2.5 g glucose (dextrose) + 2.5 g sodium hydroxide + 1 mL 0.1% solution methylene blue to 500 mL water. Solution 2: Add 5 g glucose + 5 g NaOH + 1 mL 0.1% solution methylene blue to 500 mL water. Note that the blue colour of Solution 2 disappears faster than in Solution 1. The blue colour appears at the surface of the solutions because of oxygen in the air. Shake the flasks and the blue colour returns.
2. Solution 2: Dissolve 0.05 g of methylene blue in 50 mL 0.1% ethanol. Solution 2: Dissolve 6 g of sodium hydroxide (or 8 g potassium hydroxide), in 300 mL water in a conical flask at room temperature above 25oC. Stir to dissolve then the add 5 mL of Solution 1. The blue solution turns colourless. Close the flask and shake to dissolve air in the solution, or pour the solution from a height. The colour changes to blue then fades back to colourless. Repeat the shaking many times and note the colour changes. Leave the solution for some hours and shake again. The solution turns yellow and no colour change occurs after shaking.
Repeat the experiment but instead of shaking the flask, pass nitrogen gas or natural gas through the solution. No colour change occurs because oxygen was not dissolved as in the shaking.
3. Repeat with other dyes:
3.1 Phenosafranine solution is red when oxidized and colourless when reduced. Use 6 drops of 0.2% solution in water that becomes pink on shaking and colourless when standing, after some time.
3.2 Phenosafranine, 6 drops of 0.2% solution in water, and methylene blue, 20 drops of 0.1% solution in ethanol, becomes pink on shaking and purple with more shaking then blue. On standing the sequence of colours reverses.
3.3 Indigo carmine solution becomes red-brown on gentle shaking and pale green on more shaking. On standing the sequence of colours reverses.
3.4 Resazurin (red to colourless) is dark blue when first added to the solution to be tested then becomes pale blue then becomes purple-pink on shaking.
Resazurin has dichromatism (polychromatism), where the hue of the colour depends both on the concentration of the absorbing substance and the thickness of the medium the light passes through.
16.3.5 Silver mirror tests for aldehydes, Tollens' tests for acetaldehyde
See 5.1: Tollen's reagent
Be careful! Silver salts are expensive! Do not keep the Tollens' reagent after the test because it can explode on standing. Prepare the Tollens' reagent, just before doing the test and after doing the test wash the unused Tollens' reagent down the sink with lots of water. Do this test in a fume cupboard.
Clean a test-tube with water and acetone. Add Tollens' reagent then 3 drops of acetaldehyde. Warm the test-tube in a beaker of water and a silver mirror of silver deposits. You can "silver plate" small objects or coins.
CH3CHO (aq) + Ag2O (s) --> CH3COOH (aq) + 2 Ag (s)
16.3.6 Silver mirror tests for aldehydes, Tollens' tests for glucose
Dissolve 2.8 g of silver nitrate in 170 mL of deionized water to prepare an approximate 0.1 mol per litre solution. Dissolve 3.7 h potassium hydroxide in 85 mL of deionized water to prepare an approximate 0.8 mol per litre solution. Dissolve 0.75 g of glucose in 17 mL deionized water. Add drops of 880 ammonia to the silver nitrate solution in a test-tube until a brown precipitate forms. Continue adding about 5 mL of the 880 ammonia until the precipitate dissolves leaving a colourless solution of Tollens' reagent containing the ion Ag(NH3)2+ (aq). Add the glucose solution to the Tollens' reagent and shake the test-tube until the solution turns brown then forms a silver mirror on the inside of the test-tube. The aldehyde glucose reduces the Ag+ (aq) ions to silver metal. Pour the contents of the test-tube down the sink and flush it down the sink with plenty of water.
C6H12O6, i.e. as aldehyde CH2OH(CHOH)4CHO (aq) + 2Ag(NH3)2+ (aq) + 3OH- (aq) --> 2Ag (s) + CH2OH(CHOH)4CO2- (aq) + 4NH3 (aq) + 2H2O (l)
Show that this test reaction does not occur with propanone, a ketone.
16.3.7 Fehling's tests for aldehydes in solution
16.3.1a Aldehydes, ketones, quinones | See 16.3.8: Ketones
See diagram 16.3.7: Potassium sodium tartrate
1. Fehling's solution (Hermann von Fehling 1812-1835), should be made just before the estimation of sugar test as follows:
Fehling's A solution: 69.28 grams copper (II) sulfate pentahydrate dissolved in 1 litre of distilled water
Fehling's B solution: 346 grams Rochelle salt (potassium sodium tartrate tetrahydrate), and 120 grams sodium hydroxide in 1 litre of distilled water
Add Fehling's B solution to 1 mL of Fehling's A solution until the blue precipitate just dissolves to give a deep blue solution. Fehling's reagent is used as an oxidizing agent to detect reducing sugars, e.g. (+) glucose, fructose, and aldehydes, e.g. methanal (formaldehyde). After boiling, the deep blue Fehling's solution is reduced to a yellow-red (brick-red) precipitate of copper (I) oxide, Cu2O. Ketones (except alpha hydroxy ketones) do not react with Fehling's reagent.
Rochelle salt (potassium sodium tartrate tetrahydrate, Seignette's salt), is a double salt, [KNa(C4H4O6).4H2O], that has a cooling saline taste and is piezoelectric.
2. Add 3 drops acetaldehyde solution and boil the solution until the red copper (I) oxide precipitate indicates the presence of a reducing agent.
CH3CHO (aq) + 2CUO --> CH3COOH + Cu2O (s)
3. Add drops of methanal (formaldehyde) solution (formalin), HCHO, to a test-tube one quarter filled with Fehling's reagent 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). Methanal is a strong reducing agent. The ketones do not react with Fehling's reagent. Be careful! Formaldehyde as at concentrations above 0.1 ppm in air it can irritate the eyes and mucous membranes, cause headaches, difficulty breathing or aggravate asthma symptoms. Students should not do this test.
4. 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).
5. Repeat the experiment using acetaldehyde instead of formalin. Note the similar reaction. In this reactions, the aldehyde is oxidized to carboxylic acids and the Cu2+ ion (cupric ion), complexioned with tartrate ion is reduced to Cu+ ion (cuprous ion).
RCHO + 2Cu2+ + 4OH- --> RCOOH + Cu2O + 2H2O>
6. Benedict's test is more sensitive than Fehling's test, and is easier to do because only one solution is needed, but it may be more expensive.
7. A reducing sugar acts as a reducing agent by giving electrons to other molecules. Reducing sugars are monosaccharides or disaccharides with a free ketone group, -CO-, e.g. fructose, or a free aldehyde group, -CHO, e.g. glucose. So fructose is a ketose or ketohexose and glucose is an aldose or aldohexose. Sucrose is not a reducing sugar because of the linkage of aldehyde and ketone groups between the component sugars glucose and fructose.
Tests for reducing sugars use mixtures of mild oxidizing agents
Fehling's tests for reducing sugars and aldehydes uses a tartrate ion-Cu2+ complex
Benedict's tests for reducing sugars uses a citrate ion-Cu2+ complex. Nowadays, Benedict's test is used instead of Fehling's tests for detecting reducing sugars. Tollens tests for aldehydes, the silver mirror test, uses Ag+ in ammonia solution.
Oxidation of aldose sugars: RCH=O + 2Cu2+ (blue solution) + 5OH- --> R(C=O)O- + Cu2O (red precipitate) + 3H2O
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, C16H30O, methylcyclopentadecanone, is the perfume fixative musk from musk deer but is now produced artificially.
16.3.9 Diacetyl, 2, 3-butanedione
See: 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 ocur. The popcorn industry is considering not using diacetyl in bagged products.
16.3.10 Quinones
See diagram 16.1.4.3: Quinones
See 16.3.5.0: Polycyclic aromatics
C=O groups in an unsaturated ring, as 1, 2-quinones and 1, 4-quinones, 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 fungicidal and insecticidal properties but it is toxic to many plant species.