Quantum Mechanical Studies on Chemical Reactivity and Ballistic Chemistry. IV. CNDO/2 Calculations on Azolium Cations and on the Zwitterions Resulting from Their Deprotonation,
BALLISTIC RESEARCH LABS ABERDEEN PROVING GROUND MD
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It has been found that ring protons in positions alpha-to pyrrole-type nitrogens exchange much faster than those located beta-to such nitrogens. Adding pyridine-type nitrogens to the ring also causes a large increase in rate of exchange. As part of a program of molecular orbital calculations on chemical reactivity and ballistic chemistry, the authors have carried out CNDO2 calculations on these azolium cations and on the zwitterions resulting from their deprotonation. The calculated total one-and two-atom energy changes and charge distributions suggest that the relative CH acidities of isomeric tetrazolium cations are determined primarily by coulombic effects but in the case of isomeric diazolium cations, effects operating through the sigma-framework inductive and hybridization seem predominant. The importance of solvation and other effects involving the added nitrogen is also considered.
- Atomic and Molecular Physics and Spectroscopy