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On the NH and CH acidities of toluidine isomers: theoretical description and practical consequences for the synthesis of certain aniline dyes
Author(s) -
Lukeš Vladimír,
Hartmann Horst
Publication year - 2021
Publication title -
coloration technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 1472-3581
DOI - 10.1111/cote.12536
Subject(s) - aniline , chemistry , deprotonation , toluidine , functional group , computational chemistry , organic chemistry , polymer , ion
For the toluidine isomers, amino group acidity represents a characteristic feature of these compounds in their electric neutral state. As demonstrated by theoretical calculations based on the quantum chemistry composite G4 method and density functional theory, the CH acidity of the methyl group is hidden under NH acidity. The transformation of toluidines into their mono‐ and bi‐oxidised states significantly increases the acidity of the methyl group. This study indicates that the presence or absence of these deprotonated species in reaction mixtures will determine the CN or CC coupling toluidine products. In agreement with published synthetic approaches for aniline dyes, such as mauveine and fuchsine, the results obtained explain the alternative reaction pathways occurring during the oxidation of toluidine isomers.