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Protonation of trimipramine salts of maleate, mesylate and hydrochloride observed by 1 H, 13 C and 15 N NMR spectroscopy
Author(s) -
Somashekar B. S.,
Nagana Gowda G. A.,
Ramesha A. R.,
Khetrapal C. L.
Publication year - 2005
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1509
Subject(s) - chemistry , protonation , hydrochloride , carbon 13 nmr , nuclear magnetic resonance spectroscopy , organic chemistry , ion
Abstract Protonation of the tricyclic antidepressant drug trimipramine with maleic acid, methanesulfonic acid and hydrochloric acid was studied using 1 H, 13 C and 15 N NMR spectroscopy at natural abundance. The effect of counter ions on the protonation was compared under identical conditions of solvent, concentration and temperature using homonuclear and heteronuclear one‐ and two‐dimensional experiments. Differential protonation of the terminal tertiary amine nitrogen is determined from the indirect spin–spin couplings, chemical shifts, 13 C relaxation data and variable‐temperature experiments. In the maleate salt, only one of the acidic protons is involved in protonation, the other being associated with the anion moiety. 15 N chemical shifts of the protonated nitrogens are nearly linearly related to the p K a of the constituent acid. Copyright © 2004 John Wiley & Sons, Ltd.