2-chlorobenzoic acid, from 2-chlorotoluene

Case 2 - The Hyde Park Landfill site, located in an industrial complex in the extreme northwest corner of Niagara, New York, was used from 1953 to 1975 as a disposal site for an estimated 80,000 tons of chemical waste, including chlorinated hydrocarbons. A compacted clay cover was installed in 1978 over the landfill and a tile leachate collection system was installed in 1979. Hazardous compounds such as ortho-, meta- and para-chlorobenzoic acid toluene ortho- and meta-chlorotoluene 3,4-dichlorotoluene and 2,6-dichlorotoluene were detected in the leachate (Irvine et al., 1984). Since 1979, the existing leachate treatment system has used activated carbon as the technology for removing organic carbon. Although... 

Care must be taken to use pure o-chlorotoluene in this preparation otherwise the o-chlorobenzoic acid may be contaminated with isomeric acids which are very difhcult to remove. The o-chlorotoluene therefore should be prepared from pure o-toluidine or o-chlorotoluenesulfonic acid. 

The yield of />-chlorobenzoic acid is about 20 g. From the larger runs, starting with 750 g. of />-chlorotoluene, the yield of acid averaged 260 g. 

Cognate preparations, p-Chlorobenzoic acid. Proceed exactly as for o-chlorobenzoic acid. Use 1250 ml of water, 50 g (0.4 mol) of p-chlorotoluene (Expt 6.71) and 75 g, 37.5 g and 37.5 g (0.95 mol total) of potassium permanganate. When the oxidation is complete, steam distil the mixture to recover any unreacted p-chlorotoluene (3-4 g). Filter the reaction mixture from hydrated manganese dioxide and wash the precipitate with two 100 ml portions of water. Precipitate the p-chlorobenzoic acid in the filtrate (1) by the addition of 75 ml of concentrated hydrochloric acid. Filter the cold solution with suction, wash with cold water and dry in an oven at 100 °C. The yield of p-chlorobenzoic acid, m.p. 234-235 °C, is 55 g (89%). Recrystallisation from hot water raises the m.p. to 238-239 °C. 

A solution of 100 g. (0.58 mole) of 2-nitro-4-chlorotoluene in 500 ml. of pyridine and 390 ml. of water is heated on a steam bath under a reflux condenser while 6 portions of 43 g. each of potassium permanganate are added at intervals of 1 hour. After another 1-hour heating period, the mixture is filtered and the water and pyridine are removed from the filtrate by evaporation under reduced pressure. The residue is treated with excess aqueous sodium hydroxide solution, any oil present is removed by use of a separatory funnel, and the resulting aqueous solution is acidified with hydrochloric acid. The precipitated 2-nitro-4-chlorobenzoic acid is collected by filtration, washed with water, and dried to give 56A g. (48%) of product melting at 138-140°. 

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