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Infrared multiple‐photon dissociation spectroscopy of deprotonated 6‐hydroxynicotinic acid
Author(s) -
Stipdonk Michael J.,
Kullman Michael J.,
Berden Giel,
Oomens Jos
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6829
Subject(s) - chemistry , deprotonation , infrared multiphoton dissociation , tautomer , photodissociation , dissociation (chemistry) , infrared spectroscopy , density functional theory , infrared , photochemistry , spectroscopy , ion , ion cyclotron resonance , computational chemistry , stereochemistry , organic chemistry , cyclotron , physics , quantum mechanics , optics
RATIONALE Hydroxynicotinic acids (2‐, 4‐, 5‐ and 6‐hydroxy) are widely used in the manufacture of industrial products, and hydroxypyridines are important model systems for study of the tautomerization of N‐heterocyclic compounds. Here we determined the gas‐phase structure of deprotonated 6‐hydroxynicotinic acid (6OHNic). METHODS Anions were generated by electrospray ionization, and isolated and stored in a Fourier transform ion cyclotron resonance mass spectrometer. Infrared (action) spectra were collected by monitoring photodissociation yield versus photon energy. Experimental spectra were then compared with those predicted by density functional theory (DFT) and second‐order Møller‐Plesset (MP2) perturbation theory calculations. RESULTS For neutral 6OHNic, DFT and MP2 calculations strongly suggest that the 6‐pyridone tautomer is favored when solvent effects are included. The lowest energy isomer of deprotonated 6OHNic, in the aqueous or gas phase, is predicted to be the 6‐pyridone structure deprotonated by the carboxylic acid group. CONCLUSIONS The deprotonated, 6‐pyridone structure is confirmed by comparison of the infrared multiple‐photon photodissociation (IRMPD) spectrum in the region of 1100–1900 cm –1 with those predicted using DFT and MP2 calculations. Copyright © 2014 John Wiley & Sons, Ltd.