反应详情

100 g. of dl-cis-trans-permethric acid (consisting of 40% cis and 60% trans isomer) were stirred with 400 ml. of benzene at 27° for one hour, then the suspension was filtered. The solid product, i.e. 31 g. of permethric acid consisting of 79% cis and 21% trans isomer was worked up according to the Example (4b) for obtaining racemic cis-permethric acid. The benzene solution was evaporated to give 67.2 g. of a mixture consisting of 23% cis and 77% trans isomer which was then stirred together with extraction petroleum ether at 30° C. for 5 hours. The suspension was filtered to give 26.8 g. of dl-trans-permethric acid as a solid product containing more than 95% trans isomer.

1. filtrationthe suspension was filtered