JANUARY, 1950
8
LECTURE DEMONSTRATION EXPERIMENTS IN ORGANIC CHEMISTRY RAY Q. BREWSTER University of Kansas, Lawrence, Kansas
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advantage of enlarging the student's acqnaintance with organic chemicals and processes by lecture demonstration experiments in addition to the usual laboratory exercises is widely recognized. Yet few teachers have published lists of the laboratory experiments which they assign for student performance or of the demonstrations which supplement the laboratory and lecture work. The author, therefore, ventures to record the sets of experiments that he used for these two purposes in the aromatic series (Organic Chemistry 11) during the spring semester, 1949, for a class of 100 students. The lists vary somewhat from one semester t o another. I n order that the time consumed by the demonstrations shall not detract from the lecture it is necessary t o select experiments that can be done quickly and which fit directly into the subject of the lecture. Qualitative experiments performed in test tubes and flasks and so chosen that the results are easily visible over the room are usually the most suitable for demonstration purposes. Yield preparations, however, are not excluded. A preparation may be started and carried to' the stage of a visible result during the lecture and completed later by a student volunteer. The final crystallization or distillation is thus done by a student before the next class period, a t which time the specimen is exhibited and the yield reported. All demonstration experiments may be recorded in the latter half of the student's laboratory notebook with the notation that they were
performed as lecture demonstrations. Most of the experiments in the following lists are well known and are shown by title only. I n a few instances, brief comments regarding convenient means of conducting the experiments quickly are given. Experiments performed as yield preparations are marked with an asterisk. 1. lodobenzene Dichloride. The addition of 20 ml. of carbon tetrachloride, previously saturated with chlorine, to a solution of 2 ml. of iodobenzene in 10 ml. of carbon tetrachloride produces within one or two minutes a mass of yellow crystals of iodobenzene dichloride. 2. Sulfanation of Benzene. 9. Comparative Speed of Reacdion of Acetyl Chloride, Bazoyl Chloride, and Bazenesulfonyl Chloride with Ethyl Alcohol. 4. Benzenesulfonamide. (a) Solubility in alkali (b) Slow reaction with nitrous acid 6. Basicity of Aniline. (a) Solubility in water (b) Action upon phenolphthalein (c) Ferric chloride solution (d) Salts and double salts 6. Solid Derivatives of Aniline. (a) Acetylation ( b ) Benzoylation (c) Thiocarbanilide The use of phenyl isothiocyanate as a reagent for
JOURNAL OF CHEMICAL EDUCATION
m i n e s may be illustrated by adding a solution of 5 ml. of this reagent in 10 ml. of ethyl alcohol to 5 ml. of aniline likewise dissolved in 10 ml. of ethyl alcohol. Crystals of thiocarbanilide (diphenylthiourea) form within a few minutes. 7. Bromination of Aniline wilh Bromine Wa;er. 8. Color Reactions of Aniline. (a) Bleaching powder test (b) Dichromate color test 9. Preparation of Thioearbanilide.* Two mols of aniline (186 g.), 200 ml, of carbon disulfide, and 200 ml. of ethyl alcohol may be mixed in a wide-mouthed bottle and covered with a loose-fitting cap. The bottle may then he set aside and the growth of thiocarbanilide crystals observed from day to day. After two weeks one of the students may volunteer to filter, wash, and dry the product. 10. Preparation of pBromoacetanilidt. * 11. Preparation of pNitrosodimethylaniline.* 18. Reactions of Diazolized Aniline. (a) Formation of iodobenzene (b) Coupling with phenol (c) Formation of diazoaminobenzene. 13. Reactions ofPheno1. (a) Solubility in hot and cold water (b) Ferric chloride color test (c) Bromination with bromine water (d) Benzoylation (e) Phenol-formaldehyde resin 14. Preparation of Anisole.* 15. Comparative Reducing Power of Phenol, Resoreinol, Hydroquinone, and Pyrogallol with Fehling's Solulion. 16. Properties of Benzaldehyde. (a) Reaction with ammonia (b) Addition of sodium bisulfite (c) Formation of benzaldehyde phenylhydrazone. (Acetic acid is a convenient solvent.) (d) Dihenzalacetone 17. Benzophenone Ozime. The oxime of benzophenone may be prepared easily by adding a solution of 10 g. of sodium hydroxide in 50 ml. of water to a solution of 5.4 g. of benzophenone and 6 g. of hydroxylamine hydrochloride in 70 ml. of ethyl alcohol and boiling the combined solutions for forty minutes in a flask fitted with a reflux condenser. At the end of this period 300 ml. of water is added. The oilv dro~letsof unchanged benzophenone may be removed-by stirring the suspension with finely divided charcoal and filtering. When the filtrate is cooled with ice and acidified with
dilute sulfuric acid a white precipitate of beneophenone oxime is obtained. Its solubility in alkali may be used to show the acidic character of the oxime. 18. Preparation of Benzom* In order to demonstrate the benzoin condensation a solution of 21 g. of benzaldehyde and 3 g. of potassium cyanide in 50 ml. of ethyl alcohol may be boiled under reflux for forty minutes and then chilled in ice. A student may volunteer to filter, wash, and dry the product and report the yield. 19. Quirtone.* A specimen of this important compound may be easily obtained by warming to 60' to 70" a solution of 10 g. of hydroquinone, 5.5. g. of potassium bromate, 100 ml. of water, and 5 ml. of normal sulfuric acid. The nearly black color of quinhydrone, formed as an intermediate product, gives way to the bright yellow of quinone as the oxidation proceeds. When the yellow solution is cooled in ice an excellent yield of highly pure p-benzoquinone is obtained. 80. Properties of Naphthalme. (a) Bromination (b) Sulfonation 81. Preparation of Azo Dyes. A series of azo dyes may be made by diazotizing aniline, sulfanilic acid, and P-naphthylamine and coupling these diazonium salts in alkaline, or faintly acid, solution with phenol, resorcinol, dimethylaniline, P-naphthol, and other aromatic amino or phenolic compounds. 88. Color Changcs in Dyes. The changes of color of azo and triphenylmethane dyes in acid, alkaline, and reducing solutions are fitting accompaniments for a discussion of the properties of dyes and indicators. 83. Vat Dyeing with Indigo. $4. Properries of Furfural. (a) Reduction of Tollens' solution (b) Reaction with ammonia 86. Properties of Pyridine. (a) Basicity (b) Ferric chloride solution. (c) Addition of methyl iodide. The assigned laboratory experiments included the following preparations: bromobenzene, nitrobenzene, m-dinitrobenzene, aniline, acetanilide, identification of an unknown amine, pnitroacetanilide, p-nitroaniline, m-nitroaniline, sulfanilic acid, chlorobenzene (Sandmeyer), toluene (deamination of ptoluidiue), hydrazobenzene and benzidine, phenol, ortho- and para-nitrophenol, acetophenone, triphenylcarbinol, cinnamic acid, benzoic acid, p-nitrobenzoic acid, salicylic acid and aspirin, methvl oranw, malachite ereen. fluorescein a i d eosin, and quinolink.
