Gas chromatographic properties of 1,3-dialkyl barbiturate derivatives.

The gas chromatographic properties of 1,3-dialkyl barbiturates have been studied. The retention times for 56 different 1,3-dialkyl derivatives of both aprobarbital and phenobarbital, and for 65 different 1,3-dialkyl derivatives of secobarbital were determined by gas-liquid chromatography (GLC) using a 3% SE-30 column. Retention times were found to increase with the number of carbons added. A plot of the log of the retention time versus the number of carbons in the alkyl group added for 3-alkyl derivatives of 1-alkylbarbiturates was made for each of the three barbiturates studied. A linear relationship was found to exist for derivatives having butyl or greater groups attached to the second nitrogen of the 1-alkylbarbiturates. The slopes of the graphs for the 3-alkyl derivatives of 10 different 1-alkylbarbiturates for each barbiturate studied were all found to be identical with a similar plot for straight chain hydrocarbons. This linear relationship allowed calculation of the retention times of large N,N-dialkyl barbiturates, such as N,N-eicosanylsecobarbital, which are not readily synthesized or chromatographed.