The Reduction of Silver Ions by Hydroquinone

Abstract

From the acetylation of 134 g. (1.25 moles) of o-toluidine in benzene by acetic anhydride there was obtained 135 g. of the acet-o-toluidide melting a t 108'. Bromination in about 50-g. lots, by the procedure of Bogert and Hand,I4 gave an 80% yield of the bromo-acet-o-toluidide. This was nitrated by fuming nitric acid.16 The acetyl group was removed by hydrolyzing 25-g. lots of the nitrated product with 30 cc. of concd. hydrochloric acid in 120 cc. of ethyl alcohol, and the yield was 52 g. of bromo-amine melting at 134" (all the initial 135 g. of acet-o-toluidide being used in the successive reactions). The amino group was then replaced by bromine in essential accordance with the procedure of Holleman,16 to give 23 g. of 2,5-dibromo-3nitrotoluene melting a t 6$-69' after crystallization from petroleum ether (b. p. 6048').A mixture of 14.2 g. (0.048 mole) of 2,5-dibromo-3nitrotoluene and 6.86 g. (0.052 mole) of potassium phenoxide was heated for three hours at 170". The cooled reaction mixture was shaken with ether and water, and the residue obtained by evaporation of the ether was crystallized from petroleum ether (b. p. 60-68') to give 12 g. or an 81% yield of 2-nitro-4-bromo-6-methylphenyl ether melting a t 92-94'.The nitro group was reduced by dissolving 12 g. (0.039 mole) of the compound in 150 cc. of dry ether to which 20.85 g. (0.093 mole) of stannous chloride had been added, and then saturating the resulting solution with hydrogen chloride a t 0'. The hydrochloride separated as a light brown solid (10.9 g.), and this was diazotized without further purification. Finally, the diazonium solution was added slowly to 150 cc. of boiling 50% sulfuric (16) Holleman, Rcc. trav. chim., I T , 155 (1908). towski, Bey., 16, 869 (1892).acid contained in a 500-cc. distilling flask which was connected to a condenser so that volatile products could be collected by steam distillation during the addition of the diazonium solution. The yield of 2-bromo-4-methyldibenzofuran was 4 g., and the compound crystallized from alcohol in the form of needles melting at 106-106.5".Anal. Calcd. for Cp.HoOBr: Br, 30.62. Found: Br, 30.43, 30.23. 2-Bromo-4-methyldibenzofuran was converted quantitatively to 4-methyldibenzofuran by shaking with hydrogen in the presence of palladium-calcium carbonate catalyst. The authors are grateful to Jack Swislowsky for this experiment.The bromomethyl compound was unaffected by refluxing for four days with alkaline potassium permanganate, a mixture of potassium permanganate and dilute nitric acid a t 180" for eight hours, and an alkaline solution of potassium ferrocyanide a t reflux temperature for twelve hours. When treated with an acetic acid solution of chromic acid for four hours a t 50°, the compound was partially destroyed but no acid could be isolated, and some unchanged compound was recovered. In the same solution a t the boiling point, the compound was completely destroyed. The use of chromic acid in dilute sulfuric acid also destroyed the compound without stopping a t the desired dibenzofuranca...

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