✍ Scribed by Hans Dahn; Jean-Claude Farine; Thi Thanh Tâm Nguyên
No coin nor oath required. For personal study only.
The p__K__ 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__=3.40) shows a marked crowding effect, absent in the isomeric tertiary amines 13 and 14. Tri‐p‐nitrotritylamine (10a) (p__K__=3.10), N, N‐dimethyl‐tri‐p‐nitrotritylamine (10b) (p__K__=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.
📜 SIMILAR VOLUMES
## Abstract The COSMO‐RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for realistic solvation simulations, has been used for the prediction of base pK~a~ constants. For a variety of 43 organic bases the directly
The relative basicities in solution ofthe methylamines have been calculated using the model of Miertus, Scrocco and Tomasi to describe the solvent effect. The surface of the cavity is defined with the GEPOL method. The ab initio calculations have been performed using a 4-31G basis set. The relative
N.m.r. spectra (lH and 13C) have shown that, of three inososes studied, the 2,3,4,6/5-isomer exists in solution as the keto form, and the 2,4,6/3,Sisomer is partially, and the 2,3,5/4,6\_isomer is almost fully, hydrated. In alkaline solution, each of the inososes rapidly loses a molecule of water, t