Group contribution study on ion-association extractability of ring-alkylated N-alkylpyridinium ions

Abstract

Twenty-six derivatives of alkyl-N-alkylpyridinium ions, where the alkyl groups were the methyl, ethyl and propyl groups, were synthesized. These pyridinium ions (C+) could be extracted into chloroform as their ion associates with Cl2-EO(dichloro derivatives of Ethyl Orange, A), and thus each extraction constant [formula omitted] was obtained in this work. the longer the alkyl chains, the larger the values of log Kex were. the contribution of a methylene group to log Kcx was on average 0.59 for alkyl groups substituted at a pyridine ring, and 0.54 for N-alkyl groups. the position effect (Pp) was 0.11 and 0.28 for 3-substituted and 4-substituted derivatives, respectively. the overlapping effect (Po) occurred between an N-alkyl group and a 2-substituted group, and was estimated to be -0.20. [formula omitted] must be considered for pairs of ethyl groups, and ethyl and propyl groups. the extractability parameter of the skelton [formula omitted] was determined to be an average 2.2, which is 0.75 smaller than the value of [formula omitted] calculated by using the contribution value of the methylene group, 0.59. This difference is almost the same as that in the benzene ring, 0.64, and is considered to be the effect of ring closure. © 1993, The Japan Society for Analytical Chemistry. All rights reserved.