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On the Basicity of Triarylmethylamines in Solution
Author(s) -
Dahn Hans,
Farine JeanClaude,
Nguyên Thi Thanh Tâm
Publication year - 1980
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19800630405
Subject(s) - chemistry , nitrobenzene , solvation , inductive effect , acetonitrile , aryl , base (topology) , additive function , acetic acid , medicinal chemistry , group (periodic table) , solvent , alkyl , organic chemistry , mathematical analysis , mathematics , catalysis
The p K α *of 11 triarylmethylamines (tritylamines), eight of which are new, and some related bases were measured in methylcellosolve/water 80:20 (MCS); some were also measured in dioxane/water 60:40 (Dx), acetonitrile (An), nitrobenzene (Nb) and acetic acid (Ac). (1) The influence of the aryl groups on the basicity is essentially additive; (2) In different solvents, similar linear free energy relationships were found, with differences in p * characteristic of solvation; (3) The influence on basicity of substituents of the aryl groups follows Hammett 's relationship. These results indicate a preponderance of inductive effects. N, N ‐Dimethyltritylamine (3b) (p K a MCS =3.40) shows a marked crowding effect, absent in the isomeric tertiary amines 13 and 14 . Tri‐ p ‐nitrotritylamine (10a) (p K a MCS =3.10), N, N ‐dimethyl‐tri‐ p ‐nitrotritylamine (10b) (p K a Ac =0.50), and 3b are particularly weak bases; the base‐weakening effect of the trinitrotrityl group is similar to that of the cyanomethyl and trifluoroethyl groups.