THE MULTIPLE nature op bios 723 (3 g.) was boiled for an hour, the color changed to dark red; but after the mixture was filtered and the pyridine and benzaldehyde were distilled at 5 mm. pressure, a mere trace of residue was obtained, which gave a faint reduction with Fehling's solution.Attempts to Prepare Benzoin with Other Catalysts.-In Table VIII are given the substances which, when boiled with diluted alcohol and benzaldehyde, failed to form benzoin. After the reaction mixture had been heated for the stated time, the solvent was evaporated and the bulk of the remaining benzaldehyde distilled with steam. The residual oil was then tested for benzoin with Fehling's solution, the test being negative in each case.Action of Hydrochloric Acid on Benzaldehyde.-Benzaldehyde readily absorbs dry hydrogen chloride, with the development of much heat. The liquid assumes a dark red color, and fumes in the air. A mixture of 90 g. of benzaldehyde and 3 g. of hydrochloric acid was allowed to stand for three weeks, but no benzoin was formed. A mixture of 200 g. of benzaldehyde and 12 g. of hydrochloric acid after three weeks was shaken with water, then washed with a very little sodium bicarbonate solution, and distilled; 195 g. of constant-boiling benzaldehyde was recovered. The slight distillation residue gave no test for benzoin. Summary 1. The condensation of benzaldehyde (2 moles) into benzoin (1 mole) requires the combined action of hydroxyl and of cyano ions.2. These catalysts also reverse the condensation; but at the same time, they convert benzoin into benzyl benzoate, and then into benzyl alcohol and benzoic acid. This step is not reversible.3. Heating; to 300°converts benzoin partially into benzaldehyde; but heating benzaldehyde yields no benzoin; instead, benzyl benzoate, etc., are formed.4. A consistent explanation is given for the benzoin and Cannizzaro condensations.5. A simplified method of preparing benzoin without the use of alcohol is described.

No abstract

No abstract