1,2,4-Trichlorobenzene → 3,6-Dichlorosalicylic acid

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The compound 2-methoxy-3,6-dichlorobenzoic acid is a valuable herbicide and is used in commerce for the control of a variety of undesirable vegetation. The prior art discloses in U.S. Pat. No. 3,013,054 that the 2-methoxy-3,6-dichlorobenzoic acid is prepared from 1,2,4-trichlorobenzene in a three-stage process. The trichlorobenzene is first converted to 2,5-dichlorophenol with methanol and sodium hydroxide. The phenol is then treated with carbon dioxide under pressure to yield 2-hydroxy-3,6-dichlorobenzoic acid. The hydroxy acid is then methylated with dimethyl sulfate or methyl chloride to yield the desired product.

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