A quantum-chemical study of hydration of heterosubstituted pyridinium cations

Hydration of N-ethyl-2-methyl-5-vinylpyridinium (NE2M5VP(+)) and N-butyl-2- methyl-5-vinylpyridinium (NB2M5VP(+)) was modeled by the PM3 quantum-chemic al semiempirical method. Data on the structural, charge, and energy charact eristics of the cations in the gas phase were obtained. It was shown that, in monohydrated cations, the ion-water distance increased and the energy of ion-water interactions decreased under the action of hydrophobic radicals. The ion-water interaction energy was, nevertheless, higher than the II-bon d energy calculated by the PM3 method. Water coordination was determined fo r water molecules most strongly bound with the cations in the I+(H2O)(n) sy stems, where n = 1-9, and I+ = NE2M5VP(+) or NB2M5VP(+).