GB814271A - Method for the purification of n,n-dimethylacetamide - Google Patents

Abstract

N : N-dimethylacetamide is separated from a mixture containing it and acetic acid by adding chlorobenzene, toluene, ethylbenzene, or xylene to the mixture, heating the resultant mixture to a temperature sufficient to vaporize and thereby remove the azeotrope of acetic acid and substituted benzene and recovering the N : N-dimethylacetamide from the residue. Preferably enough of the substituted benzene is added to enable all of the acetic acid to be distilled off, alternatively less of the substituted benzene may be used and as a result the N : N-dimethylacetamide contains on distillation a proportion of acetic acid which may be removed if required by the addition of further substituted benzene and azeotropic distillation. In a typical example (No. 1) 500 grams of a mixture of N : N-dimethylacetamide and acetic acid containing 29.6 per cent of the latter was mixed with 400 grams of ethylbenzene and a distillate removed until a head temperature of 128 DEG C. was obtained. An additional 466 grams of ethylbenzene was then added continuously. By distilling the residue at 85-86 DEG C. and under 50 mms. mercury pressure, N : N-dimethylacetamide containing 0.013 per cent of acetic acid is obtained.