Bromo-3-methylbenzoic Acid

2-BROMO-3-METHYLBENZOIC ACID (m-Toluic acid, 2-bromo-) 

Submitted by J. F. Bunnett and M. M. Rachut.1 Checked by John D. Roberts and Marc S. Silver. 

2-Bromo-4-nitrotoluene. In a 200-ml. three-necked, round-bottomed flask provided with an efficient reflux condenser bearing a suitable trap for absorbing hydrogen bromide, a 100-ml. separatory funnel, and a ball-joint or mercury-sealed mechanical stirrer are placed 68.5 g. (0.5 mole) of -nitrotoluene (Note 1) and 1.0 g. of iron powder. The mixture is heated to 75-80° by means of a water bath, vigorous stirring is begun, and 30.5 ml. (92.0 g., 0.57 mole) of bromine is added over the course of 30 minutes. After the addition of bromine is complete, the reaction mixture is maintained at 75-80° with continuation of stirring for an additional 1.5 hours. 

The reaction mixture is poured with vigorous stirring into 750 ml. of ice-cold 10% sodium hydroxide solution, the solid is 

2-Bromo-3-methylbenzoic acid. Caution This procedure must be carried out in a hood with a good draft, because poisonous hydrogen cyanide gas is evolved. In a 5-1. round-bottomed flask are placed 90 g. of potassium cyanide, 900 ml. of 2-ethoxyethanol (Note 3), 850 ml. of water, and the moist 2-bromo-4-nitrotoluene obtained above. A reflux condenser is attached, and the mixture is boiled for 16 hours (Note 4). To the hot, dark-red solution is then added 1.51. of water, and the mixture is acidified with concentrated hydrochloric acid. (Caution Hydrogen cyanide is evolved.) The acidified mixture is boiled for 15 minutes to expel hydrogen cyanide and then allowed to cool to 35-40°. Five grams of diatomaceous earth is stirred in, and the mixture is filtered through a Buchner funnel precoated with a little diatomaceous earth. The solid is discarded, and the filtrate is extracted three times with 200-ml. portions of chloroform. The chloroform extracts are combined and extracted with three 100-ml. portions of 5% ammonium carbonate solution. The basic extracts are combined, acidified with concentrated hydrochloric acid, and cooled in an ice bath. The oil which first forms soon crystallizes. 

---

Bromo methylbenzoic acid isobutyl ester fenpyroximate p Bromo nitro benzene chlorbromuron 4 Bromophenol silafluofen a Bromo a phenyl acetone diphacinone Bromo pinacolone diclobutrazol, triadimefon Bromo propane penconazole... 

P Metl lbenzoic acid 3-Bromo methylbenzoic acid... 

Bromo-2-heptene, 38, 8 a-Bromoisobutyryl bromide, 33, 29 -Bromomandelic acid, 36,11 2-Bromo-3-methylbenzoic acid, 38,... 

Although 2-bromo-4-nitrotoluene has been obtained by several routes, it is most easily prepared by bromination of />-nitro-toluene.2 The procedure given is adapted from that described by Cavil .3 2-Bromo-3-methylbenzoic acid has not been prepared by any other means evidence for its structure is presented elsewhere.4... 

Problem 15.36. Draw a structural formula for each of the following compounds (a) 3-chlorobutanoic acid, ib) 4-methylpentanoic acid, (c) 2-bromo-4-methylbenzoic acid, id) 3-methylcyclopentanecar-boxylic acid. 

---