The basicity of pyridine and its tendency towards cationic homoconjugation in non-aqueous media
✍ Scribed by Lech Chmurzyński
- Publisher
- Journal of Heterocyclic Chemistry
- Year
- 2000
- Tongue
- English
- Weight
- 298 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0022-152X
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✦ Synopsis
Abstract
Acid dissociation constant, pK~a~, of protonated pyridine, determined in the polar protophobic aprotic solvent, acetone, has been compared with pK~a~ values of the pyridinium ion in a variety of other polar solvents including aprotic protophobic ones, acetonitrile, benzonitrile, nitrobenzene, nitromethane, and propylene carbonate, in the protophilic aprotic dimethyl sulfoxide and N,N‐dimethylformamide, as well as in the amphiprotic methanol. On the basis of the set of these pK~a~ values, the effect of the medium on the basicity of pyridine is discussed. Further, based on the cationic homoconjugation constants of pyridine conjugated with the pyridinium cation in the non‐aqueous solvents, the tendency of pyridine towards homoconjugation reactions has also been discussed. Finally, both the basicity of pyridine and its tendency towards cationic homoconjugation has been compared with analogous properties of pyridine N‐oxide.