School Science Lessons
Topic 16b Amines and alkaloids, aromatic hydrocarbons, dioxins, esters. food molecules, oleoresins, organic chemistry terms, proteins, peptides, amino acids
2012-02-01a SP
Please send comments to: J.Elfick@uq.edu.au
Table of contents
See: Angiosperms, and other common plants, in School Science Lessons, common names first
16.3.6.2 Amines and alkaloids
16.8.0 Aromatic hydrocarbons
16.14.0 Dioxins, Agent orange, polyvinyl chloride
16.5.1.0 Esters, derivatives of fatty acids
19.2.24 Food molecules
16.3.5.1.0 Oleoresins "gums"
16.11.0 Organic chemistry terms
16.6.1.1 Proteins, peptides, amino acids
16.3.6.2 Amines and alkaloids
16.3.6.2 Amines and alkaloids
16.3.6.2.1 Pyridine-piperidine
16.3.6.2.2 Tropane
16.3.6.2.3 Pyrrolizidine
16.3.6.2.4 Isoquinoline
16.3.6.2.5 Quinolizidine
16.3.6.2.6 Quinoline
16.3.6.2.7 Phenethylamine
16.3.6.2.8 Indole
16.3.6.2.9 Indolizidine
16.3.6.2.10 Steroid
16.3.6.2.11 Purine
16.3.6.2.12 Thiazole
16.3.6.2.13 Capsaicin
16.3.6.2.14 Ephedrine
16.3.6.2.15 Muscarine
16.8.0 Aromatic hydrocarbons
16.8.1 Reactions of benzene, C6H6
16.8.2 Prepare ferric tannate with tea leaves
16.8.3 Extraction of caffeine and benzoic acid from soft drinks, e.g. cola and lemonade
16.5.1.0 Esters, derivatives of fatty acids
16.5.1.0 Esters, derivatives of fatty acids, (RCOOR'), Esters group: (-COOR), Suffix: -oate
16.5.1.1 Ethyl acetoacetonate, (ethyl 3-oxobutanoate)
16.5.4 Hydrolysis of esters
16.5.2 Prepare ethyl acetate, (ethyl ethanoate), See 1.
16.5.6 Prepare amyl acetate, (pear oil)
16.5.1 Prepare ethyl chloride
16.5.7 Prepare ethyl butyrate
16.5.8 Prepare ethyl acetate, (ethyl ethanoate), See 2.
16.5.9 Prepare methyl chloride
16.5.5 Prepare methyl salicylate, (oil of wintergreen)
16.5.10 Rubbing alcohol, surgical spirit
16.3.5.1.0 Oleoresins "gums"
16.3.5.1.0 Oleoresins "gums"
16.3.5.1.5 Amber
16.3.5.1.2 Balsams
16.3.5.1.3 Incenses
16.3.5.1.4 "Natural lacquer"
16.3.5.1.6 Phenolic resins
16.11.0 Organic chemistry terms
16.11.01 Alkyl group
16.11.1 Alkyd resin
16.11.2 Alkylation
16.11.3 Alkyne group
16.11.4 Catenation
16.11.5 Citric acid cycle, Krebs cycle
16.11.6 Conjugated
16.11.7 Denature
16.11.8 Epoxy, epoxy resin
16.11.9 Esterification
16.11.10 Fume cupboard, fume hood, fume cabinet
16.3.6.3 Glycoproteins
16.11.11 Hydrogenation
16.11.12 Hydrolysis
16.11.13 Peptides
16.11.14 Phosphorylation
3.6.0 Polymer terminology
16.11.15 Racemic
16.11.16 Sulfonation
16.11.17 Tautomer
16.6.1.1 Proteins, peptides, amino acids
16.6 17 Hydrolysis of urea with urease
16.6.9 Nitrogen in an organic compound, Kjeldahl method
16.6.3 Prepare protein solutions
16.6.12 Proteins are amphoteric
16.6.15 Reactions of urea with nitrous acid
16.6.16 Reactions of urea with soda lime
16.6.14 Reactions of urea with sodium hypochlorite
16.6.18 Urea acts as a base
16.6.13 Urea forms biuret
19.2.24 Food molecules
19.2.10 Albumen (egg white) and egg yolk
19.2.24 Butter
Caffeine
19.2.21a Choline
19.2.26 Custard
19.2.10.2 Egg in a cake mix
19.2.18 Iron from breakfast cereal
19.2.21 Fish smell, trimethylamine, choline
19.2.14 Food colouring liquids and detergent
19.2.27 Garlic
19.2.17 Glycoalkaloids, avoid bruised or green potatoes
19.2.28 Harmful substances in cigarette smoke
19.2.15 Heat starch, glycemic index
19.2.9.1 Jelly using fresh pineapple and tinned pineapple
19.2.22 Laundry starch
4.2.2 Make sauerkraut (activity for primary grade 4 students, about 9 years old)
4.2.1 Make yoghurt (activity for primary grade 4 students, about 9 years old)
4.2.1a Make yoghurt, a report from Turkey
4.3.17 Make yoghurt, test milk quality
19.2.23 Milk, Contents
19.2.23.1 Milk, Test for the fortification of milk with calcium carbonate
19.2.9 Pectin in jelly and jam
19.2.13 Prepare fruit salts
16.10.4 Prepare wood gas and wood tar
16.10.4.1 Distil wood, (destructive distillation)
19.2.12 Salad dressing and mayonnaise emulsions
10.5.5 Steam distillation to find water and fat content of food
19.2.29 Toxic effect of common drugs on Daphnia
19.2.30 Tests for chewing gum quality by comparing bubbles
19.2.22.1 Wheat starch and gluten
19.2.11 Yeast, fermentation, brewing, whisky, fish sauce
16.3.5.1.0 Oleoresins "gums"
Oleoresins come from gymnosperm trees from the nonvolatile diterpene residue called rosin.
16.3.5.1.2 Balsams, hard varnishes and fragrant perfumes have oleoresins containing volatile essential oils and nonvolatile resins, e.g. "Canada balsam", natural turpentine used in microscopy because the refractive index is similar to the refractive index of glass.
See 2.4: Canada balsam
16.3.5.1.3 Incenses containing strong-scented oleoresins, e.g. frankincense, myrrh,
16.3.5.1.4 "Natural lacquer", poison ivy, and shellac form from resinous excretions of the lac insect, (Tachardia lacca).
16.3.5.1.5 Amber is made of nonvolatile terpenes from subterranean deposits of resin from pine trees, a yellow, translucent, fossilized vegetable resin., (Hymenaea courbaril).
16.3.5.1.6 Phenolic resins of hashish the pure resin of marijuana, contain volatile monoterpenes and sesquiterpenes + phenolic cannabinoids, e.g. psychoactive delta-tetrahydrocannabinol, (THC), an alcohol.
16.3.6.2 Amines and alkaloids
See 16.3.6.4: Alkaloids produced by plants from amino acids
See diagram 16.20.0: Caffeine, cocaine, coniine, heroin, LSD, morphine, nicotine, quinine, strychnine, theobromine, theophylline
See diagram 16.20.1: Codeine, heroin, methadone, morphine, nicotine, pethidine
See diagram 16.21.7: Mescaline, dopamine, psilocybin, serotonin, ergine, LSD, tropane
See diagram 16.21.8: Tryptamine, THC, Tetrahydrocannabinol, marijuana
Amines are organic derivative of ammonia, NH3, where one, two or three hydrogen atoms are replaced by alkyl groups as a primary amine, secondary amine or tertiary amine, e.g. trimethylamine CH3NCH3CH3. Amines are weak bases that form ammonium salts that are more soluble in water than the original amine, e.g. cough medicine may contain the cough suppressants dextramethorphan hydrobromide or the decongestant, expectorant, pseudoephidrine hydrochloride and ephedrine. Alkaloids have the properties of amines and are natural bitter, alkaline, nitrogenous compounds, nitrogenous organic bases in plants They usually contain one or more N and a heterocyclic ring structure. The names of alkaloids usually end in "ine". Their function is probably to defend against grazing animals or being eaten by insects. Many alkaloids are plant metabolic by-products derived from amino acids. more than 10 000 different alkaloids may exist in over 300 plant families. Alkaloids often contain one or more phenolic or indole rings, usually with a nitrogen atom in the ring. The term alkaloid was first used to describe chemical bases from plants used in medicines, but now there is no exact definition of alkaloid. Some classifications of alkaloids are based on structure and some on origin.
Alkaloids
16.3.6.2.1 Pyridine-piperidine group of alkaloids: (single carbon ring with one nitrogen atom), arecaidine, coniine, guvacine, nicotine, pilocarpine, piperine, sparteine, trigonelline
16.3.6.2.2 Tropane group of alkaloids, tropine group of alkaloids
See diagram 16.20.0: Cocaine
(methylated nitrogen atom, N-CH3), 5-hydroxytryptamine, conotoxin, decaline, ecgonine, hygrine, hyoscyamine, novocain, pelletierine, scopolamine ("truth drug"), tetramine, tetrodoxin.
Atropine, C17H23NO3, from deadly nightshade, jimsonweed, mandrake, and atropine sulfate, used in anticholinergic medicines, cardiac arrest treatment, and to dilate pupils for eye examination.
Cocaine, C17H21ON4, from coca shrub
16.3.6.2.3 Pyrrolizidine group of alkaloids: e.g. retronecine a 2,4-D, 2,4,5-Th
16.3.6.2.4 Isoquinoline group of alkaloids
(2 carbon rings one containing a nitrogen atom), (morphine, codeine and thebane from opium poppy, (D-tubocurarine from curare, Chondodendron), berberine, diacetylmorphine, hydrastine, narceine, narcotine, papaverine, podophyllotoxin, reticuline, heroin, vinblastine, vincristine
16.3.6.2.5 Quinolizidine group of alkaloids
(2 carbon rings with one nitrogen atom), (cytisine from Cytisus and Sophora and Agave for tequila), erythroidine, (lupinine from Lupinus), sparteine.
16.3.6.2.6 Quinoline group of alkaloids
(2 rings containing one nitrogen atom), (quinine from Cinchona), echinopsone, atabrine, brucine, cevadine, chloroquine, primaquine, veratrine.
16.3.6.2.7 Phenethylamine group of alkaloids
See diagram 16.21.6: anthocyanin, catechin, catechol, mescaline, tyrosine, DOPA, (dihydroxyphenylalanine), | See diagram 14.03: Amphetamine, epidephrine
e.g. DOPA, (dihydroxyphenylalanine), catecholamines [CH4(OH)2 = catechol ring], e.g. dopamine, (3-hydroxy tyramine), adrenaline, (epinephrine), noradrenaline, (norepinephrine), substituted phenethylamines, e.g. catecholamine ether, guaiacol, (HOC6H4OCH3, 2-hydroxyphenol, 1,2-hydroxybenzene).
16.3.6.2.8 Indole group of alkaloids
Double ring containing an indole group of alkaloids
See diagram 16.21.8: THC, tetrahydrocannibinol, tryptophan
Ecstasy, methylenedioxymethamphetamine, MDMA, (ergine, d-lysergic amide, from ergot fungus, Claviceps), LSD (lysergic acid diethylamide), LSA d-lysergic acid diethylamide, bufotenine, (5-hydroxydimethyltryptamine), DMT, ergine, MDMA, (ecstasy), mescaline, methamphetamine, NMT, psilocybin, (reserpine from Rauwolfia), serotonin, strychnine, tryptamine, (vinblastine and vincristine from Catharanthus), (strychnine from Strychnos nux-vomica), (podophyllotoxin from may apple.)
Serotonin, 5-hydroxytryptamine, indole group of alkaloids, affects nerves in the brain, mood
See diagram 16.21.7
Dopamine and LSD affect the level of serotonin.
Ecstasy, MDMA, 3, 4-methylenedioxymethamphetamine, may cause long-term damage to the serotonin system.
16.3.6.2.9 Indolizidine group of alkaloids
Two rings including an indole ring, (swainsonine from Swainsona and locoweed, stagger weed, Astragalus)
16.3.6.2.10 Steroidal group of alkaloids
Two rings containing one nitrogen atom + 4 carbon ring steroid, solanidine, (from Solanum), triterpene, zygadenine
16.3.6.2.11 Purine group of alkaloids
Double carbon ring containing 4 nitrogen atoms
See diagram 16.21.0: Purines, purine, uric acid adenine, guanine, caffeine, theobromine, theophylline
16.3.6.2.12 Thiazole group of alkaloids
Single carbon ring containing one nitrogen atom and one sulfur atom
See diagram 16.21.11: Thiazole, thiamin, (vitamin B), penicillin basic structure.
16.3.6.2.13 Capsaicin group of alkaloids
Capsaicin from Capsicum chilli
See: Capsaicin | See diagram 16.21.12: Capsaicin
Capsaicin is used as a topical counter-irritant analgesic cream for osteoarthritis pain in adults only, e.g. "Axsain".
16.3.6.2.14 Ephedrine group of alkaloids
See diagram 16.20.0: Colchicine
Amine alkaloids: bufotenine, ficin, papain, bromelain
Ephedrine from Ephedra, (pseudoephedrine, isomer of ephedrine)
Mescaline from cactus species, e.g. Trichocereus
Colchicine, C22H25O6N, Extremely toxic by all routes
Colchicine, Solution < 0.1% Not hazardous
Colchicine alkaloid, from autumn crocus
Colchicine inhibits cell division because is a mitosis spindle poison and medicine for gout.
16.3.6.2.15 Muscarine group of alkaloids
Group one carbon ring and one nitrogen atom, e.g.  muscarine, muscimol, (muscimole), from agaric mushroom Amanita.
16.3.6.3 Glycoproteins
Glycoproteins are complex polypeptides + polysaccharides chains. They are involved in cell recognition in T-cells, blood cell antigens, antibodies and pollen recognition. Immunotoxins are conjugated proteins monoclonal antibodies with an attached lectin protein. Lectins called haemagglutinins occur in red kidney beans and may cause intestinal problems when eaten if the beans are not first soaked and cooked thoroughly.
16.14.0 Dioxins, Agent orange
See diagram 16.14.0: Dioxins
Dioxins are group of substances harmful to living things in small concentrations. The term dioxins generally refers to a series of chlorinated dioxins, e.g. 2,3,7,8-tetracholorodibenzo-p-dioxin, (2,3,7,8-TCDD), by-product of manufacture of herbicide 2,4,5-T and occurred in the Agent Orange defoliant used in the Vietnam War, 1954-75 . They are chlorinated hydrocarbon compounds called dibenzo-p-dioxins. They are very toxic and persist in the environment for long periods. They are produced during incineration of wastes and are a contaminant in chemical manufacturing processes. They interfere with the action of hormones and the genetic system even in very small concentrations. They accumulate in the fat cells but are not metabolized. They damage the immune system, leading to increased susceptibility to infectious disease. When chemicals and plastics are manufactured or burned, dioxin may be produced as a by-product and dumped into landfill. Landfill gas may include dioxins which may spread into the community if landfill gas, mainly methane is burned as a source of energy. An important source of dioxins is from burning polyvinyl chloride in incinerators. Agent orange was widely thought to be the cause of infant birth defects of children in Vietnam and in US military families.
16.5.1.0 Esters, derivatives of fatty acids, (RCOOR'), Esters group: (-COOR), Suffix: (-oate), Esters, (RCOOR', R(C=O)OR'), (-oate), derivatives of fatty acids: ethyl ethanoate, (ethyl acetate), (CH3COOC2H5, CH3C=OOCH2CH3), [glyceride, (acyl glycerol), fatty acid ester of glycerol: HOCH2CH(OH)CH2OH]
Esters include methyl buranoate apple, ethyl methanoate rum essence, ethyl butanoate pineapple oil, pentyl ethanoate banana, octyl butanoate orange, methyl salicylate oil of wintergreen, amyl acetate pear oil.
16.5.1 Prepare ethyl chloride
Ethyl chloride, (C2H5Cl), is an alkyl halide.
See 16.2.2: Halogen compounds, haloalkanes, (alkyl halides), | See diagram 1.13: Smelling chemicals
Pour ethyl alcohol or methylated spirit into a test-tube. Note the odour. Test the liquid with litmus paper. No colour change occurs. Add dilute hydrochloric acid. Heat the mixture gently by putting the test-tube in hot water. Smell any gas coming from the test-tube.
Be careful! Do not inhale gases directly from the test-tube. Fan the gas towards the nose with the hand and sniff cautiously. If no odour is detected, move closer and try again.
Cool the mixtures and add drops of concentrated sulfuric acid. Heat the mixture gently by putting the test-tube in hot water.
Be careful! Smell for not more than one second. The gases may cause general anaesthesia. Note the sweet "ethereal" smell.
The heated sulfuric acid acts as a catalyst.
HCl (aq) + C2H5OH (l) --> C2H5Cl (g) + H2O (l)
hydrochloric acid + ethanol --> ethyl chloride + water
16.5.1.1 Ethyl acetoactonate, (ethyl 3-oxobutanoate), ethyl ethanoate + sodium ethoxide --> ethyl acetoacetonate, (3-oxobutanoate), CH3COCH2COOC2H5, (acetoacetic ester), (hydrolysis + acid), --> acetoacetic acid, (3-oxobutanoic acid), CH3COCH2COOH, (unstable beta-keto acid), CH3COCH2COOH → CH3COCH3 + CO2
acetoacetic acid --> acetone + carbon dioxide
16.5.2 Prepare ethyl acetate, (ethyl ethanoate) 1
Alcohols react with organic acids to produce esters and water. Esters are non-electrolytes, so they must be heated to speed the reaction. Sulfuric acid is used for a dehydrating agent and catalyst to join the other portions of the reactant alcohol and acid to produce the ester. Ethyl ethanoate, (ethyl acetate, acetic ether [CH3COOC2H5]), is a colourless liquid with a fruity smell used as a solvent for lacquers and paints. Esters of low molecular mass have fruity smells and are found in flavours and perfumes. The semi-structural formula is R1COOHR2. R = alkyl groups, e.g. R1 = CH3 and R2 = C2H5. When you heat a mixture of ester and water it produces a mixture of alkanoic acid and alkanol in an equilibrium mixture.
Mix other organic acids with an alcohol.
Add drops of concentrated sulfuric acid then heat the test-tube gently in hot water. Note the odour of the ester, e.g. pentyl ethanoate smells of apricots and octyl acetate smells of oranges. Add five drops of ethanoic acid, (glacial acetic acid), to five drops of ethyl alcohol with one drop of concentrated sulfuric acid as a catalyst. Heat the test-tube gently. Note the fruity odour of ethyl acetate and the sharp odour of acetic acid.
alkanol + alkanoic acid <--> ester + water
R1COOH + R2OH <--> R1COOR2 + H2O
organic acid + alcohol <--> ester + water
CH3COOH + C2H5OH <--> CH3COOC2H5 + H2O
ethanoic acid + ethanol <--> ethyl ethanoate + water
(acetic acid + ethyl alcohol <--> ethyl acetate + water)
16.5.4 Hydrolysis of esters
See 12.12.0: Soaps and synthetic detergents
1. Add acid to an ester.
The H+ of the acid catalyses the hydrolysis.
CH3COOC2H5 + HOH, (H2O) --> CH3COOH + C2H5OH
2. Add alkali to an ester. This is called saponification because the reaction is used to prepare soap.
CH3COOC2H5 + NaOH --> CH3COONa + C2H5OH
16.5.5 Prepare methyl salicylate, (oil of wintergreen)
Methyl salicylate, (oil of wintergreen, HOC6H4COOMe), has the odour of "oil of wintergreen" ans is used for liniments. Add 1 g of salicylic acid to a mixture of 1 mL of methyl alcohol and three drops of sulfuric acid in a test-tube. Heat the test-tube gently and note the odour of the ester produced by the reaction.
methyl alcohol + salicylic acid --> methyl salicylate, (oil of wintergreen)
16.5.6 Prepare amyl acetate, (pear oil)
Amyl acetate, (pear oil, pentyl ethanoate, CH3COOC5H11), has the odour of bananas or pears. Mix 5 mL of ethanoic acid, (acetic acid), 3 mL of pentan-1-ol, (amyl alcohol, n-pentyl alcohol, C5H11OH), and 1 mL of sulfuric acid in a test-tube. Heat the test-tube gently and note the odour of the ester produced by the reaction.
amyl alcohol, (l) + acetic acid --> amyl acetate, (banana or pear oil)
16.5.7 Prepare ethyl butyrate, (pineapple oil)
Ethyl butyrate has the odour of pineapples. Mix in a test-tube 1 mL of concentrated sulfuric acid and 2 mL of ethanol. Add 2 mL of n-butyric acid, (butanoic acid, C3H7COOH). It smells like rancid butter. Heat the test-tube gently and note the odour of the ester produced by the reaction.
ethyl alcohol + butyric acid, (l) --> ethyl butyrate, (pineapple oil)
16.5.8 Prepare ethyl acetate 2
1. Repeat the above experiment with two drops of glacial ethanoic acid, (acetic acid), in place of the ethanol. Connect a delivery tube from the test-tube to a solution of limewater. Tests for carbon dioxide during the reaction. The odour of acetic acid disappears. The reaction produces ethyl acetate.
2. Mix 2 mL ethyl alcohol with 3 mL acetic acid in a test-tube. Add 3 drops concentrated sulfuric acid. Heat the mixture gently by immersing the test-tube in hot water. Cautiously note the odour of the ethyl acetate produced and compare it with the odours of ethyl alcohol and acetic acid. Ethyl acetate has a fragrant odour different from the wine-like odour of ethyl alcohol and the sharp odour of acetic acid.
[heated with sulfuric acid] ethyl alcohol, (l) + acetic acid, (aq) --> water (l) + ethyl acetate (aq)
16.5.9 Prepare methyl chloride
Pour 5 mL methyl alcohol and 5 mL ethyl alcohol into separate test-tubes. Note their odours. Drop small pieces of red and blue litmus paper into each liquid. Add to each about 5 mL of dilute hydrochloric acid. If you see no visible signs of reaction, warm each mixture gently by standing the tube in hot water for 5 minutes. Cautiously smell any gas that may be coming from the test-tubes.
Be careful! Sulfuric acid is a corrosive chemical!
Cool the mixtures and add a few drops of concentrated sulfuric acid to each test-tube. If you see no visible signs of reaction, warm each mixture gently by standing the tube in hot water for 5 minutes. Cautiously smell any gas that may be coming from the test-tubes. Avoid smelling for more than one second any gases liberated, since one of them can cause general anaesthesia when inhaled in sufficient quantity. Although there is no apparent reaction when hydrochloric acid is mixed with either of the two alcohols, after heating the mixture with concentrated sulfuric acid, a reaction occurs shown by the production of a gas with a sweetish "ethereal" smell.
[heated with sulfuric acid] methyl alcohol (l) + hydrochloric acid (aq) --> water (l) + methyl chloride (g)
16.5.10 Rubbing alcohol, surgical spirit
In many countries, rubbing alcohol is not isopropyl alcohol, (propan-2-ol), but is specified mixture of ethanol and water. Surgical spirit is a methylated spirit, i.e. ethyl alcohol denatured with methyl alcohol to prevent its use as an alcoholic beverage. Different brands of surgical spirit may also contain other liquids. It is used to clean body surfaces before surgery. However, some people use the term surgical spirit for isopropyl alcohol.
16.6.3 Prepare protein solutions
Shake the white of an egg in its own volume of water. Squash peas in water, filter and use the filtrate. Make a gelatine solution from a commercial "jelly" preparation Collect solid proteins, e.g. hair, feathers. Test on a microscope slide: plant juices, meat, soup, pieces of tissue, sunflower seed.
16.6.9 Nitrogen in an organic compound, Kjeldahl method
Be careful! Do this experiment in a fume cupboard.
Add 10 mL of concentrated sulfuric acid to 0.5 g of urea in a long necked flask, (Kjeldahl Flask). Add potassium hydrogen sulfate to raise the boiling point of the acid and complete the decomposition of the protein. Boil in a fume cupboard for 10 minutes. Leave to cool then add 100 mL water. Add strong sodium hydroxide solution, (30%), and anti-bumping granules. Distil the mixture. Tests for ammonia in the distillate. For volumetric titration, pass all the ammonia through 1 M acid solution. The ammonia neutralizes some acid. Titrate the acid left over with an alkali to find how much acid used by the ammonia.
Repeat the experiment with 5 g egg albumen, (egg white).
H2SO4 (aq) + 2NH3 (g) --> (NH4)2SO4 (aq)
16.6.12 Proteins are amphoteric
Amino acids are amphoteric in that they contain both acidic and basic groups in their molecules. Proteins dissolve in alkalis and in concentrated solutions of acids. In alkaline solutions proteins are negatively charged. In strongly acid solutions proteins are positively charged. They are uncharged at the iso-electric point and are precipitated. At pH higher than the iso-electric point, a protein acts as an acid. At pH lower than the iso-electric point the protein acts as a base. When acting as an acid a protein forms a fast colour with a basic dye, e.g. methylene blue. When acting as a base, a protein reacts with an acid dye, e.g. eosin.
To show the amphoteric nature of a protein, prepare four test-tubes, two containing eosin, and two containing methylene blue.
1. Add a white feather or white wool to each test-tube. Add 3 drops of acetic acid to one eosin solution and 3 drops of concentrated ammonia solution, (ammonium hydroxide), to the other eosin solution. Leave to stand for five minutes. Wash the feather or wool and note the fast dyeing in the eosin and acid solution. The protein acted as a base in the presence of the acid, and reacted with the acid dye eosin.
2. Add 3 drops of acetic acid to one of the methylene blue solutions and 3 drops of concentrated ammonia solution, (ammonium hydroxide), to the other methylene blue solution. Leave to stand for five minutes. Wash the feather or wool or feather and note the fast dyeing in the alkaline solution. The protein acts as an acid in alkaline solution and reacts with the basic dye methylene blue.
16.6.13 Urea forms biuret
Heat some crystals of dry urea slowly in a test-tube until the liquid which forms solidifies again as the white solid biuret. Dissolve the biuret in water for use in the biuret reaction.
2NH2.CO.NH2 --> NH2.CO.NH.CO.NH2 + NH3
16.6.14 Reactions of urea with sodium hypochlorite
Dissolve crystals of urea in the minimum amount of water. Add drops of sodium hypochlorite solution. Nitrogen gas forms. Carbon dioxide gas also forms but it dissolves in the alkaline solution.
NH2.CO.NH2 + 3NaOCl --> N2 + 2H2O + 3NaCl + CO2
16.6.15 Reactions of urea with nitrous acid
Add an equal volume of dilute hydrochloric acid to a saturated solution of sodium nitrite. Cool under the tap. When the effervescence has moderated, add drops of a solution of urea. Nitrogen gas forms.
NH2.CO.NH2 + 2HNO2 --> 2N2 + CO2 + 3H2O
16.6.16 Reactions of urea with soda lime
Heat a mixture of urea and soda lime. Test the gas formed for ammonia.
NH2.CO.NH2 + 2NaOH --> 2NH3 + Na2CO3
16.6.17 Hydrolysis of urea with urease
Dissolve urea crystals in water. Add a tablet of urease or soya flour and keep at 40oC for a minute. Tests for ammonia. The enzyme, urease, hydrolyses the urea.
NH2.CO.NH2 + H2O --> 2NH3 + CO2
16.6.18 Urea acts as a base
Add an equal volume of concentrated nitric acid to a saturated solution of urea. The white precipitate is urea nitrate, (NH2.CO.NH2.HNO3).
16.10.4 Prepare wood gas and wood tar
See diagram: 16.10.4
When heating sawdust strongly in a hard glass test-tube, the gas coming out of the test-tube can be ignited. This gas is called wood gas. It contains carbon monoxide, hydrogen gas, methane, and other gases. The oily dark brown liquid left in the bottom of the test-tube is called wood tar. It contains wood alcohol, propanone, (acetone), ethanoic acid, (acetic acid), and other substances. If sawdust is heated without any air, the residue will be wood charcoal.
Fill a sidearm test-tube one half full of wood chips, (or sawdust), and fit a one-hole stopper with a delivery glass tube into the test-tube. When heating, observe that the wood chips gradually become black and an oily dark brown liquid flows through the side arm of the test-tube. Use a lighted match to ignite the gas coming out of the delivery tube. The gas can burn steadily. Note that the volume of the product is very small. The residue is charcoal, (carbon).
16.10.4.1 Distil wood, (destructive distillation)
Distil wood in a furnace. Condense the products in copper tubing to produce charcoal, pyroligneous acid, wood alcohol, propanone, (acetone), and ethanoic acid, (acetic acid).
16.11.01 Alkyl group
Alkyls are saturated hydrocarbons, e.g. methyl, ethyl ...
Alkyls, symbol R, name ends in -yl, named from alkanes by removing an H from the formula, e.g. methane CH4 becomes the alkyl called methyl CH3-.
16.11.1 Alkyd resin
Adhesive and coating resins made from glycerol and unsaturated organic acids. Rigid cross-linked polymers are formed when there are more than two functional groups on linear chain monomers. They are use in paint enamels and making dentures.
16.11.2 Alkylation
Alkylation is replacing a hydrogen on a cyclic compound with an alkyl CH3 or longer chain group, by heating isobutane with the lower boiling point alkenes, C3-C6, under acid conditions. To add the isobutane to the alkene and form a larger branched alkane and so converting some lower boiling gas fractions into high octane fractions. For example:
CH3 H+ CH3
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CH2=CH-CH3 (alkene) + CH3-C-H (isobutane) --> CH3- C-CH2-CH2-CH2 (branched chain alkane)
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CH3 CH3
16.11.3 Alkyne group
Alkyne R1-C =-CR2, (CnH2n-2, triple carbon bonds, =-), Prefix: alkynl-, Suffix: -yne (no principal functional group), also called acetylenes
16.11.4 Catenation
Formation of chains of atoms
16.11.5 Citric acid cycle, Krebs cycle
A cycle of reactions in mitochondria as part of aerobic cell respiration in which oxaloacxetic acid is regenerated by a series of reactions in which ADP is converted to energy rich ATP as part of the energy conversion processes in the body.
16.11.6 Conjugated
Alternating double and single bonds. Note that polyunsaturated chains have "cis-methylene interrupted" or "skipped" double bonds.
16.11.7 Denature
Destroy structure of a protein by heating or oxidation. The tertiary structure of a protein collapses, denatured, by heating, acid or agitation in air.
16.11.8 Epoxy, epoxy resin
Epoxy compounds, (O atoms in CCO ring), Epoxy resin polymers, thermoset plastics: 3.4.3.1
Oxygen directly linked to two adjacent bonded carbon atoms forming a triangle. Epoxy hardener, e.g. diethylenetriamine / methyl isobutyl ketone ketamine mixture, fumes may be toxic if heated. Epoxy resins are the uncured resins used for fibreglass and may contain isocyanate residues that are strong irritants
to the eye nose and respiratory organs. Epoxy resins are easy to ignite, orange yellow smoky flame, burns after removing flame, acrid smell. Araldite polymer is an epoxy resin. (Epoxy hardener, H180 FAST, H180 SLOW, Epoxy resin DER353).
16.11.9 Esterification
Forming an ester, reaction of organic acid with an alcohol. Reverse process is ester hydrolysis, saponification, the making of soap from fat.
16.11.10 Fume cupboard, fume hood, fume cabinet
Enclosed reinforced cupboard with facilities for chemical reactions and used under negative air pressure.
16.11.11 Hydrogenation
Addition of hydrogen to a molecule to convert unsaturated molecules to saturated and reducing double bonds to single bonds.
16.11.12 Hydrolysis
Splitting a molecule using a reaction with water
16.11.13 Peptides
Amides derived from two or more amino carboxylic acid molecules by formation of a covalent bond from the carbonyl carbon of one to the nitrogen atom of another with loss of water. Peptides include structures formed from alpha-amino acids and from any amino carboxylic acid. C = any organyl group.
16.11.14 Phosphorylation
Phosphorylation means adding a phosphate group to a molecule.
16.11.15 Racemic
A one-to-one mixture of left handed and right-handed, chiral, forms of the same molecule. Most chemical reactions produce products as racemic mixtures, whereas biological reactions generally produce one or the other form only. R,R" The R designates an undefined organic group, e.g. a hydrocarbon chain. The R it is not necessarily the same as R".
16.11.16 Sulfonation
Addition of the function group -SO3H to a molecule
16.11.17 Tautomer
When an atom, e.g. hydrogen, moves backwards and forwards between different places on a molecule, the new and original molecules form a tautomeric pair.
16.8.1 Reactions of benzene, C6H6
Pyrene, C16H10 (4 benzene rings), coal tar, toxic, in burnt barbecued food
Benzopyrene, C20H12, carcinogenic, lung cancer and throat cancers, in pitch, volcanoes, cigarette smoke, wood smoke, burnt barbecued food
See 16.3.4.0: Aromatics, aromatic compounds | See diagram 16.8.1: Benzene compounds:
1. Add 1 mL bromine water to 5 drops of benzene in a test-tube. The bromine water is not decolorized, unlike ethylene and acetylene with bromine water.
2. Put 5 drops of benzene in 2 test-tubes. In one of the test-tubes add iron filings. Add 3 drops of bromine water to each test-tube., Hydrogen bromide forms in both test-tubes but more in the test-tube containing the iron filings ha acts as a catalyst.
C6H6 + Br2 --> C6H5Br + HBr
3. Add 5 drops of benzene to 1 mL of acidified potassium permanganate solution. The permanganate solution decolorizes only when the mixture is heated. The benzene is oxidized to lower molecular weigh molecules.
4. A reaction mixture of concentrated nitric acid and concentrated sulfuric acid in a Leibig condenser reacts with benzene at over 300 K in a nitration reaction, (substitution of a -NO2 group for a hydrogen atom in an arene ring), to form nitrobenzene. The sulfuric acid in not included in the equation because it acts as a sort of catalyst.
HNO3 + H2SO4 --> NO2+ + H2O + 2HSO4-
C6H6 + NO2+ --> C6H5NO2 + H+
benzene + nitric acid --> nitrobenzene + water
C6H6 + HNO3 --> C6H5NO2 + H2O
Late in the reaction, 1,3-dinitrobenzene forms, C6H4(NO2)2, but on cooling to room temperature it separates as a solid from the liquid nitrobenzene.
16.8.2 Prepare ferric tannate with tea leaves
Tannin is a mixture of organic chemicals related to polyhydroxy-benzoic acids. Tannin has a bitter taste and is astringent, i.e. it contracts the mouth. It is found in the bark and other tissues of many plants probably to control grazing. It is used to prepare black ink and leather from animal hides.
1. Add 200 g, (2 tea bags), of dried tea to 250 mL of boiling water.
2. Add an unused pad of steel wool to 100 mL of vinegar, boil for 10 minutes, then strain through cotton wool in a filter funnel. Leave to cool then add 1 mL of hydrogen peroxide solution to produce a brown red, indicating iron, (III).
3. Add equal volumes of solution 1. to solution 2. to produce a black solution of ferric tannate.
2H+ + Fe --> Fe2+ + H2
2H+ + 2Fe2+ + H2O2 --> 2Fe3+ + 2H2O
Fe3+ + tannic acid --> ferric tannate
16.8.3 Extraction of caffeine and benzoic acid from soft drinks, e.g. cola and lemonade
See 1.10.0A: Purine group of alkaloids, caffeine
1. Isolation of caffeine
Add 2 g of sodium carbonate to 50 mL of a cola, (kola), drink in a 1 litre conical flask. Add 50 mL of dichloromethane, (methylene chloride), and swirl gently for five minutes. Do not shake. Transfer into a separating funnel and leave to settle for 10 minutes). Drain the lower methylene chloride layer into a 250 mL conical flask. Add 50 mL more dichloromethane to the separating funnel and enclose with a stopper. Carefully invert the separating funnel 3 times to allow any remaining caffeine to be extracted into the dichloromethane layer. Again drain the lower methylene chloride layer into the 250 mL conical flask. Add 5 g of anhydrous magnesium sulfate to remove the water when it forms insoluble hydrated magnesium sulfate. Filter the now clear dichloromethane through cotton wool pad into a 250 mL beaker. Evaporate the dichloromethane on a water bath in a fume cupboard or distil it off to recover the solvent. Weigh the remaining precipitate. Test the precipitate by putting a small amount on a watch glass and mix with 3 drops of concentrated hydrochloric acid. Be careful! Add small crystals of potassium chlorate. Mix with a glass rod and evaporate to dryness on a water bath in a closed fume cupboard. Leave the watch glass to cool then moisten the residue with 2 drops 2 M ammonia solution. The residue turns purple.
2. Isolation of benzoic acid
Pour half a drink-can of lemonade is poured into a 1 L conical flask and add 2 drops of dilute hydrochloric acid. Add 50 mL dichloromethane then swirled gently for five minutes. Pour into a separating funnel and leave to allowed to settle for 5 minutes. Drain the solvent layer into a 100 mL beaker and leave to evaporate in a fume cupboard. A residue of benzoic acid remains.
19.2.9 Pectin in jelly and jam
See 16.3.1.8: Pectin
If it contains too much pectin, it flows slowly, so add sugar. If the pectin is low add apples that are high in pectin to assure gelation. Measure fruit juice pH. Best gelation if pH between 3.1 and 3.4. If pH is too high, the jelly is watery and will not set.
19.2.9.1 Gelatine in jelly with fresh or tinned pineapple
Jelly, "Jello", is not recommended with pineapple Ananas comosus, papaya Carica papaya, figs Ficus carica, guava Psidium guajava, kiwi fruit Actinidia chinensis, and ginger root Zingiber officinale because they contain proteolytic enzymes which prevent the gelatine from setting.
Prepare two small jellies, one containing crushed fresh pineapple, the other containing crushed tinned pineapple. Leave to set. When the tinned pineapple jelly is firmly set, shake the jelly containing the fresh pineapple. It has not set well because the fresh pineapple contains enzymes that digest protein in the jelly. The enzymes in the tinned f pineapple have become inactive because of heating and processing.
19.2.10 Albumen (egg white) and egg yolk
The texture of egg yolk and egg white, albumen, is because of the dissolved globular proteins with outer charges that attract water molecules and prevent other proteins from clumping them together. However, when egg are heated, as in making scrambled eggs, the globular proteins unravel, denature, exposing the inner charges on the proteins causing the S-H groups on the amino acid cysteine to oxidize and from covalent disulfide bonds, disulfide bridges. So the scrambled egg becomes hard and loses water.
1. An egg beater forms foam better at room temperature than when chilled. If beaten too much, the foam breaks and becomes liquid. Add sugar and cream of tartar to stabilize the egg foam. Add fat to cause the foam to collapse.
2. Heat the white albumen of an egg. Observe how it turns from slimy watery white to chalk white in a firmly cooked egg. The protein loses surrounding water and shrinks. The reaction is irreversible. You cannot dissolve the solid egg white in water.
3. Proteins can be denatured by heat or weak acid solutions which destroy the hydrogen bonds and cause tertiary proteins to uncoil, e.g. vinegar, acetic acid, can "cook" an egg white, albumen, without heat.
19.2.10.2 Egg in a cake mix
Use a cake recipe that requires use of one egg. Use the same recipe for making four cakes but with no egg, one egg, two eggs and three eggs. Eat the four cakes and describe the taste and texture of each cake.
19.2.11 Yeast, fermentation, brewing, whisky, fish sauce
See 3.38: Carbon dioxide and fermentation for brewing
1. To make whisky, barley is soaked in water then allowed to germinate until roots and shoots form. During this germination enzymes are produced that can convert starch to fermentable sugars. The germinated grain, (green malt), is then dried over a smoky peat fire to stop further germination. The malt is ground to form grist that is mixed with hot water then put in a large container, a mash tun, for further germination to form a weak alcoholic solution, to be distilled into casks to form whisky. The taste of whisky comes mainly from the smoke of the peat fire.
2. "Dried yeast", (active granules), baker's yeast, living yeast, contain "bakers' yeast", an emulsifier, e.g. emulsifier 491, potato flour and a vegetable gum, e.g. 414.
3. In sauerkraut manufacture, lactic acid bacteria convert sugar in cabbage into 2-hydroxypropanoic acid, (lactic acid).
4. Fermented fish sauce, garum, made usually from anchovies, tuna, eel and mackerel, was popular during the Roman empire and is still made in Vietnam and other Asian countries.
19.2.12 Salad dressing and mayonnaise emulsions
1. Mix oil and water then shake. The oil and water separates and settles according to the different densities. Add a surfactant and shake. An emulsion forms. If the surfactant is egg yolk, i.e. lecithin, the emulsion is salad dressing. Beat the mixture hard to obtain small droplets so that the emulsion becomes mayonnaise.
2. Beat an egg yolk until it becomes thick. Add lemon juice or vinegar. Slowly add olive oil while stirring. A stable emulsion forms.
19.2.13 Prepare fruit salts
Mix 0.45 kg icing sugar, (fine sugar), 113 g cream of tartar, 113 g tartaric acid, 113 g carbonate of soda, 2 g Epsom salts. Mix thoroughly and sift twice. Put in glass jar and seal jar tightly. Add one teaspoon fruit salts to 0.28 L water and drink without delay!
19.2.14 Food colouring liquids and detergent
Use a dish of milk, three food colour liquids and a little detergent. Put two drops of three different food colouring liquids into the three corners of a dish of milk. Quickly add two drops of detergent into the fourth corner and observe. Look for common features, especially patterns that are seen when this experiment is least or most active. Later, another drop of detergent can be added.
19.2.15 Heat starch, glycemic index
The glycemic index is a ranking of carbohydrates based on their immediate effect on blood glucose, (blood sugar), levels. It compares foods gram for gram of carbohydrate. Carbohydrates that breakdown quickly during digestion have the highest glycemic indexes. The blood glucose response is fast and high. Carbohydrates that breakdown slowly, releasing glucose gradually into the blood stream, have low glycemic indexes
Heat a mixture of starch and water by pouring boiling water on it while stirring. The colour turns from chalk white to nearly water white because the starch grains have burst and let the starch out. This is similar to making the starch more soluble and more digestible.
19.2.17 Glycoalkaloids, avoid bruised or green potatoes
See 16.3.6.4: Alkaloids produced by plants from amino acids
Some glycoalkaloids, e.g. alpha solanine and alpha chaconine, are toxic compounds in plants from the Solanaceae family, e.g. potato, tomato, capsicum, tobacco. Potato tubers in sunlight form glycoalkaloids when amyloblasts change to chloroplasts. Potatoes should be stored in cool dark places where air circulates, but not in a refrigerator. The alpha solanine has a bitter taste and the alpha chaconine is the more toxic. Toxicity is caused by anticholinesterase activity on the central nervous system and membrane disruption which irritates the gastro-intestine of the digestive system. Do not purchase green, bruised, insect-damaged or cut potatoes. Pregnant women should especially avoid eating damaged potatoes to avoid possible birth defects due to glycoalkaloids. Potatoes should not be displayed under strong fluorescent light in supermarkets. Potatoes can be irradiated to delay sprouting and prevent greening but not prevent the production of alpha solanine. Cooking does not destroy the glycoalkaloids.
19.2.18 Iron from breakfast cereal
Powdered iron is added to breakfast cereal to "fortify" it. We can digest some of it when the iron filings are oxidized in the stomach and later absorbed by the small intestine. Iron is necessary for production of haemoglobin. During production of the cereal in the factory very tiny particles of food grade iron are added to the dry cereal. The A steelworks could make a small nail from the iron in your body.
1. Crush a cup of breakfast cereal into a fine powder with a mortar and pestle. Put the crushed cereal in a plastic bag and add hot water. Stroke the bag with a strong magnet, e.g. a neodymium magnet used in electronics, towards one corner of the bag. The black fur in the corner of the bag is iron. Do not touch the cereal with the strong magnet.
2. Put a cup of cereal in a food blender. Add hot water to submerge all the cereal. After 20 minutes, hold a magnet to the side of the blender and turn it on. See the iron deposit in the blender next to the magnet.
2. Crush a serving of dry breakfast cereal, e.g. corn flakes, add water and stir in a magnetic stirrer for 10 minutes. Observe iron powder sticking to the magnetic follower. Calculate the concentration of iron in the cereal, e.g. "Special K" 20 mg per 100 g dry cereal.
3. Float flakes of breakfast cereal in water in a Petri dish on an overhead projector. Use a strong magnet to pull the flakes across the dish.
4. Attach magnetic tape to a wooden ice cream stick and wrap it in a plastic bag. Crush fortified cereal in a plastic bag, pour it into a bowl and cover it with warm water. Stir the cereal with the ice cream stick and observe the iron particles sticking to the plastic bag around the ice cream stick.
5. Crush a cup of breakfast cereal into a fine powder with a mortar and pestle. Pour the powder on a piece of paper. Move a magnet under the piece of paper and note any movement of the fine powder.
19.2.21 Fish smell, trimethylamine, choline
See diagram 16.3.3.0: Lipids, (choline)
Proteins in raw fish are denatured by citric acid, lemon juice. Freshly caught fish have no odour. However, the end products of enzyme reactions accumulate when the fish is to give the characteristic fish smell. If fish is not fresh, it give off trimethylamine, N(CH3)3, the source of fish smell. The cooked fish is less tasty and the cooking smell is offensive. To stop fish smell, soak fish in soy bean paste or milk so that proteins in them absorb the smell. Use ginger or green onion during cooking. Lemon juice, vinegar, wine, and rice wine can neutralize fish fat which contains trimethylamine. Soak freshwater fish in vinegar water before cooking. Trimethylamine is produced by bacteria in your intestines but it is broken down by an oxidation reaction in the liver. The reaction requires a certain enzyme. If people do not have the enzyme, due to a genetic fault, they may smell fishy! They suffer from a metabolic disorder called Trimethylaminuria, (TMAU). Such people can be relieved of this embarrassing problem by avoiding foods rich in the amino alcohol choline, Trimethylamine is found in beetroot and herrings so some people say it has a "herring smell". At the end of rigor mortis bacterial action may decompose the fish protein and add to the offensive smell. So fish should be eaten fresh and cooked for only ba short time to denature tissue between the fibres and heat the fish to an acceptable temperature for eating.
19.2.21a Choline
Choline, CH2OHCH2N(CH3)3OH, is found in egg yolk, liver, kidney, soya beans, peas, and whole grain wheat. Choline is an amino alcohol, a component of phospholipids, a water soluble essential lipid in cell membranes, associated with vitamin B complex.
19.2.22 Laundry starch
Make a suspension of laundry starch. The starch breaks up, but does not dissolve. Boil the suspension. The starch turns from chalk white to nearly water white because boiling burst the starch grains and let the starch out. The starch is now more soluble and more digestible.
19.2.22.1 Wheat starch and gluten
Gluten is a protein complex formed by kneading of the wheat flour dough proteins gliaden and glutenin. Gliaden is soluble in alcohol but glutenin is not.
Tie plain wheat flour in a fine cloth. Bang it repeatedly in a dish of water. Let the white suspension of starch settle in the dish and decant the water. The sticky mass left in the cloth is mainly gluten and cellulose.
19.2.23 Milk
Homogenize by breaking the fat globules. Heat milk to form a skin of protein and calcium compounds.
"Devondale", Australia, Milk, Full Cream, 100% pure, No preservatives or additives, 150 mL, Devondale milk is pasteurized at an ultra high temperature and packed in a sterile Tetra Pak package so it stays fresh for up to 9 months without refrigeration. Serve within seven days after opening.
 Homogenized milk
Contents
 Per 150 mL
 Per 100 mL
Energy
 404 kJ
 269 kJ
Protein
 5.0 g
 3.3 g
Fat, Total
 5.1 g
 3.4 g
Fat, Saturated
 3.5 g
 2.3 g
Carbohydrate
 7.7 g
 5.1 g
Sugars
 7.7 g
 5.1 g
Sodium
 60 mg
 40 mg
Calcium
 180 mg
 120 mg
RDI = Recommended Dietary Intake
19.2.23.1 Test for the fortification of milk with calcium carbonate
Experiment modified by Adrian van Ravels
See diagram 19.2.23.1: Milk fortification
1. Use a 3 mL transfer pipette to transfer 6 mL of "X brand Low Fat Milk" into a 50 mL centrifuge tube with a lid that has a flexible tube connected into it.
2. Use a 3 mL transfer to transfer 5 mL of 4.73% w/v aqueous solution of barium hydroxide into a second 50 mL centrifuge tube.
3. Use a 3 mL transfer pipette to transfer 10 mL of 6 M acetic acid into the X brand Low Fat Milk. Close the lid of this centrifuge tube and arrange the end of the flexible tube to sit below the level of the barium hydroxide solution in the other centrifuge tube. Shake this centrifuge tube with back and forth shaking or finger tapping and allow any gas produced to bubble through the barium hydroxide solution.
4. Leave the solution to stand, then shake it again until no more bubbles appear out of the end of the flexible tube. The bubbles of carbon dioxide produce a white flocculent precipitate in the bottom of barium carbonate..
5. So a carbonate exists in the X brand Low Fat Milk.
Any carbonate, CO32-, reacts with acetic acid, CH3COOH, to produce carbon dioxide, CO2, and calcium acetate Ca(CH3COO)2.
CaCO3 + 2CH3COOH --> Ca(CH3COO)2 + H2O + CO2
Carbon dioxide reacts with barium hydroxide solution, Ba(OH)2, to form a white flocculent precipitate of barium carbonate, BaCO3.
CO2 + Ba(OH)2 --> BaCO3 + H2O
19.2.23.1a To distinguish between carbonate and a bicarbonate, add excess of 1M hydrochloric acid to the precipitate to dissolve the barium carbonate back into solution if it is a carbonate, or does not dissolve the barium carbonate if it is a bicarbonate.
19.2.23.1b Tests for calcium
Calcium identification A
To confirm the presence of calcium or calcium salts in the original sample solution:
1. To 0.2 mL of a neutral solution containing a quantity of the substance to be examined equivalent to about 0.2 mg of calcium (Ca2+) per mL, add 0.5 mL of a 0.2% w/v solution of glyoxal-bis-(2-hydroxyanil) in
96% v/v ethanol.
2. Add to this mixture 0.2 mL of a 10.6% w/v solution of anhydrous sodium carbonate.
3. Shake this mixture with 2 mL of chloroform and add 2 mL of distilled water.
4. Shake the mixture again to allow the denser chloroform layer to separate from the aqueous layer.
5. A chloroform layer coloured red confirms the presence of calcium ions.
Calcium identification B.
1. Dissolve 20 mg of the substance n 5 mL of 2M acetic acid.
2. Add 0.5 mL of a 5.3% w/v solution of potassium ferrocyanide, potassium hexacyanoferrate (II). The solution remain mostly unchanged in clarity and colour.
3. Add 50 mg of ammonium chloride.
4. The formation of a white, crystalline precipitate confirms the presence of calcium ions.
19.2.24 Butter
Heat butter. The fat separates from salt and water. Heat too hot, as in deep drying. The fat cracks to form the unsaturated hydrocarbon acrid smelling tear-producing acrolein.
19.2.26 Custard
If you cook custard at too high or too low a temperature it becomes either watery or curdled.
19.2.27 Garlic
When a clove of garlic, Allium sativum, is crushed the enzyme allinase acts on alliin, (S-allylcysteine), to produce unstable allicin, (diallyl thiosulfionate), that degrades to diallyl sulfide CH2.CH.CH2.S-S.CH2.CH.CH2 and other sulfur compounds called ajoenes and dithiins. Diallyl disulfide can also be prepared by steam distillation. All these compounds are said to have health benefits owing to their anticlotting, antifungus, antibacterial and antioxidant properties. However, garlic should be eaten in oil preparations, e.g. olive oil, or cooked. Raw garlic may damage the digestive system.
19.2.28 Harmful substances in cigarette smoke
Burning, leaves of the tobacco plant give off smoke in which more than one thousand chemical substances have been identified. These substances include tobacco tar, nicotine, carbon oxide and aldehydes considered harmful to human health. Tobacco tar contains many kinds of carcinogens, e.g. benzopyrene. Nicotine is similar to hydrocyanic acid in toxicity. Excessive carbon oxide will weaken oxygen carrying capacity of blood, and lead to an oxygen deficit in body tissues. Put 10 mL of 95% alcohol in a sidearm test-tube. Fit the test-tube with a 1 hole stopper carrying a glass delivery tube, one end of which is kept under the alcohol and close to the bottom of the test-tube. Insert the other end of the delivery tube in a lighted cigarette. The smoke is drawn down through the delivery tube into the alcohol solution by an air extractor attached to the side arm of the test-tube. Some substances such as nicotine and benzidine are dissolved in alcohol to make colour of the solution change from colourless to yellow, and finally to brown along with an increase in the number of lighted cigarettes.
19.2.29 Toxic effect of common drugs on Daphnia
Be careful! Children must not taste the test solutions! Young children may be distressed by the sight of Daphnia struggling under the influence of these substances. However, such a sight can send a powerful deterrent message about substance abuse. Collect Daphnia in spring from ponds or purchase from goldfish supply shops.
1. Prepare the following test solutions in test-tubes:
1.1 10 mL coffee from a coffee cup containing 1 teaspoon of coffee powder, or the usual way you make coffee, active ingredient caffeine
1.2 10 mL cooking sherry, 17% alcohol / volume active ingredient.
2. Stir the following substances into 10 mL water at 37oC:
2.1 300 mg aspirin tablet, active ingredient acetylsalicylic acid,
2.2 1 g pipe tobacco or the contents of discarded cigarette butts, active ingredient nicotine,
2.3 1 Benadryl allergy caplet, active ingredient diphenhydramine.
3. Use an eye dropper to transfer a Daphnia to 5 test-tubes containing 10 mL pond water. Transfer 1, 2, 3, 4 drops of test solution into test-tubes 1, 2, 3, 4. Put no test solution in the control test-tube
4. Use a microscope to observe movement, heart rate and gill movement of Daphnia in control test-tube 5, then in test-tubes 1 to 4. Record the least number of drops of test solution to kill the Daphnia. Tobacco causes quick death at the lowest doses. Alcohol first slows the heartbeat rate, then is lethal at higher doses. Aspirin and allergy capsules are lethal at the highest doses. Coffee causes "racing" of the heart, heart palpitations, but is not lethal.
5. Repeat the experiment with 5.1 decaffeinated coffee, 5.2 red wine 12.5% alcohol / volume, 5.3 100 mg low dose "baby" aspirin, 5. 4. "lite" low nicotine cigarettes. This experiment does not compare the relative effects of the active ingredients because the concentration as mg/mL in the test solutions varies.
19.2.30 Tests for chewing gum quality by comparing bubbles
Chew different samples of chewing gum until the taste has gone. Apply the same exhaling force to make a chewing gum bubble. Measure the diameter of the chewing gum bubbles. Note whether the samples of chewing gum are made from chicle based on gutta-percha plasticized by triterpenes or made from poly, (vinyl acetate), PVA.