Process for separating cis and trans isomers of cyclopropane carboxylic acids
AssigneeImperial Chemical Industries PLC
InventorThomas Leigh
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Abstract
A process of separating cis and trans isomers of cyclopropane carboxylic acids comprising the step of treating an aqueous solution of a soluble salt of the cis and trans isomers with just sufficient of an acid, for example acetic acid or carbonic acid, to cause precipitation of one isomeric form of the cyclopropane carboxylic acid while substantially all or a major proportion of the other isomeric form remains in solution as the soluble salt. The process may be used, for example, to separate (+)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (an intermediate for insecticides) from a mixture of the (+)-cis and (+)-trans acids.
Claims10
A process for separating cis and trans isomers of cyclopropane carboxylic acids of formula:
- ##STR3## wherein R.sup.1 is halo, alkyl, alkenyl, haloalkyl, haloalkenyl or haloalkynyl, and R.sup.2 is hydrogen or cyano, from a mixture of cis or trans isomers, which consists essentially of the step of treating an aqueous solution of a soluble salt of the cis and trans isomers with just sufficient of an acid to cause precipitation of one isomeric form of the cyclopropane carboxylic acid whilst substantially all or a major proportion of the other isomeric form remains in solution as the soluble salt, the acid being one having a pk.sub.a lower than the pk.sub.a of the isomeric form of the cyclopropane carboxylic acid to be precipitated.
Dependencies are inferred from the claim text.