AM1 and PM3 study of the protonation tautomerization and valence tautomerization of some 4-substituted imidazoles

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Ogretir C., Yarligan S.

THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE, vol.425, no.3, pp.249-254, 1998 (SCI-Expanded)

• Publication Type: Article / Article
• Volume: 425 Issue: 3
• Publication Date: 1998
• Doi Number: 10.1016/s0166-1280(97)00168-1
• Journal Name: THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
• Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
• Page Numbers: pp.249-254
• Eskisehir Osmangazi University Affiliated: No

Abstract

The gas-phase geometries, relative stabilities, ionization potentials and proton affinities of the different tautomers of some 4-substituted imidazoles and their N-methyl derivatives were calculated with full geometry optimization. The predominance of the a (i.e. 1H-form) form with an electron-acceptor group at the 4-position over the b (i.e. 3H-form) form and the predominance of the b (i.e. 3H-form) form with an electron-donor group at the 4-position over the a (i.e. 1H-form) form were confirmed. A correlation between experimentally obtained acidity constants, pK(a), and calculated proton affinities was detected. (C) 1998 Elsevier Science B.V.