GB1283089A - Separating mixtures of stereoisomeric diaminodicyclohexylalkanes - Google Patents

Abstract

1283089 Separating diaminodicyclohexylalkanes BADISCHE ANILIN- & SODAFABRIK AG 25 Nov 1969 [26 Nov 1968] 57517/69 Heading C2C The trans,trans isomer content of a mixture of stereoisomeric diaminodicyclohexylalkanes is recovered by (a) forming the CO 2 reaction product of at least the trans,trans isomer by contacting the mixture of stereoisomers with CO 2 , heating the reaction product, in an inert diluent in which the CO 2 reaction product of the trans,- trans isomer is selectively less soluble at at least one temperature than the CO 2 reaction products of the other isomers and/or the isomers themselves, to a temperature from 110‹ to 200‹ C. at a pressure greater than the vapour pressure of the diluent and a CO 2 partial pressure of at least 0À1 atmosphere absolute, and (b) recovering the CO 2 reaction product of the trans,trans isomer by crystallization from the diluent, optionally after cooling the diluent. The trans,trans diamino-dicyclohexylalkane may be recovered from the crystallized CO 2 reaction product by heating the separated crystals of this product to a temperature of from 80‹ to 180‹ C. at atmospheric or reduced pressure. The remaining isomers of the original mixture may be rerecover from the mother liquor remaining after step (b) either by heating said mother liquor at atmospheric or reduced pressure to 80-180‹ C., or by passing an inert gas through the solution at slightly elevated pressure and recovering the isomers from the diluent by distillation. Examples are given which illustrate this process. The preparation of 4,4<SP>1</SP>-diisocyanatodicyclohexylmethane from the corresponding diamine is referred to.