Nitric Acid → 2,3-Dichloro-5-nitrobenzoic acid

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Reaction Conditions

Reaction Steps

2,3-Dichlorobenzoic acid, obtained from Aldrich, (40 g, 0.21 mole) was added portion wise to a −20° C. concentrated H2SO4, obtained from Acros, (233 mL) solution which was fitted with a mechanical overhead stirrer. During the addition process, a separate flask containing concentrated H2SO4 (50 mL) was cooled to 0° C. and fuming HNO3, obtained from Acros, (16.6 mL) was slowly added. This solution was then added dropwise to the 2,3-Dichlorobenzoic acid solution at a rate which kept the reaction mixture at or slightly below −15° C. After the addition was complete the resulting solution was allowed to warm to 10° C. over 3 hours. The crude solid material was filtered through a fritted filter funnel, washed with cold H2O (200 mL), and dried under a stream of air followed by high vacuum to yield 21.7 g (44%) of product (246) which contained 4% of the undesired regioisomer (2,3-Dichloro-6-nitrobenzoic acid 247) based on 1H NMR analysis. The filtrate was slowly poured over ice and additional solid precipitated. This solid was observed to be a 3:1 mixture of 2,3-dichloro-6-nitrobenzoic acid (247) to 2,3-dichloro-5-nitrobenzoic acid (246) based on 1H NMR analysis.

Provenance & Evidence