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Basicity of the nitrogen atom and of the carbonyl function of methyl isonicotinate and 4‐acetylpyridine. An infrared study of the interaction with proton donors
Author(s) -
Kasende O.,
Vanderheyden E.,
ZeegersHuyskens Th.
Publication year - 1985
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570220636
Subject(s) - chemistry , substituent , protonation , pyridine , ring (chemistry) , infrared spectroscopy , hydrogen bond , nitrogen atom , medicinal chemistry , nitrogen , proton , hydrochloric acid , hydrogen atom , photochemistry , stereochemistry , inorganic chemistry , organic chemistry , molecule , group (periodic table) , ion , physics , quantum mechanics
The hydrogen bonded complexes between methyl isonicotinate and 4‐acetylpyridine and phenol derivatives acting as proton donors have been investigated by ir spectroscopy. The thermodynamic parameters (K, — ΔH°, — ΔS°) have been determined. The ir data show that the hydrogen bond interaction occurs at the carbonyl function and at the nitrogen atom of the ring. When the acidity of the proton donor increases, N ‐complexation is favoured over carbonyl complexation and with the stronger acid hydrochloric acid, only N ‐protonated species are observed. The data are compared with those obtained for closely related pyridine derivatives, bearing a X‐C=O substituent and it is shown that the proportion of OH···N and OH···O=C species is related to the basicity of the nitrogen atom of the heterocyclic ring and to inductive and mesomeric effects depending on the nature of X.