Abstract: The invention concerns the separation of optical isomers of cyclopropane carboxylic acid.

Abstract: A process for separating the individual optically active isomers of cis- or trans-forms of cyclopropane carboxylic acids of formula: ##STR1## 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-isomers or trans-isomers which comprises treating an aqueous solution of a soluble salt of the racemate or diastereoisomeric mixture of the cis- or trans-isomers with just sufficient of a single isomer of an optically active amine to cause precipitation of one isomer or diastereoisomer of the cyclopropane carboxylic acid as the ammonium salt while substantially all of the other isomer remains in solution as the soluble salt.

Abstract: A process for the preparation of certain cyano substituted esters and optical isomers thereof useful as insecticides by dehydration of the precursor carboxamido esters. Intermediates for the preparation of such compounds, e.g., racemic methyl 3-phenoxymandelate, methyl (S)-3-phenoxymandelate and methyl (R)-3-phenoxymandelate are also disclosed.

Abstract: Esters of formula: ##STR1## wherein R is either (a) or a group of formula: ##STR2## where X is methyl, chlorine or bromine, or (b) a group of formula: ##STR3## where Y is methyl or chlorine and n is one or two, and R.sup.2 is alkyl or 2 to 4 carbon atoms; and R.sup.1 is phenoxy or 2,2-dichlorovinyloxy.

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.

Abstract: A process for the preparation of certain cyano substituted esters and optical isomers thereof useful as insecticides by dehydration of the precursor carboxamido esters.