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Linear free energy ortho ‐correlations in the thiophene series. Part IX . Kinetics of esterification with diazodiphenylmethane of some 3‐, 4‐, and 5‐substituted thiophene‐2‐carboxylic acids in methanol
Author(s) -
Noto Renato,
Buscemi Silvestre,
Consiglio Giovanni,
Spinelli Domenico
Publication year - 1981
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.5570180419
Subject(s) - chemistry , thiophene , benzoic acid , methanol , reactivity (psychology) , ring (chemistry) , reaction rate constant , medicinal chemistry , organic chemistry , logarithm , carboxylic acid , kinetics , computational chemistry , medicine , physics , alternative medicine , pathology , quantum mechanics , mathematical analysis , mathematics
The rate constants for the esterification of some 3‐, 4‐, and 5‐substituted thiophene‐2‐carboxylic acids with diazodiphenylmethane in methanol at 25° have been measured. The reactivity of some para‐ and ortho ‐substituted benzoic acids has also been determined. Logarithmic kinetic constants for ortho‐, meta‐ , and para ‐like substituted thiophene‐2‐carboxylic acids furnish an excellent linear free energy relationship when plotted versus Δpk a (β 0.89, r 0.989, C.L. > 99.9%, n 18, i 0.04), thus confirming the peculiar behaviour of five‐membered ring derivatives. The correlation with σ H values offers an additional proof of the hyper‐ortho character of the 2,3‐relation in thiophene derivatives. para‐ and ortho ‐Substituted benzoic acids show the usual behaviour of six‐membered ring derivatives.