Hydrogen bond geometries and proton tautomerism of homoconjugated anions of carboxylic acids studied via H/D isotope effects on 13C NMR chemical shifts

Guo J, Tolstoy PM, Koeppe B, Golubev NS, Denisov GS, Smirnov SN, Limbach HH (2012)

Publication Type: Journal article

Publication year: 2012

Journal

Journal of Physical Chemistry A American Chemical Society

Book Volume: 116

Pages Range: 11180-11188

Journal Issue: 46

DOI: 10.1021/jp304943h

Abstract

Ten formally symmetric anionic OHO hydrogen bonded complexes, modeling Asp/Glu amino acid side chain interactions in nonaqueous environment (CDF 3/CDF2Cl solution, 200-110 K) have been studied by 1H, 2H, and 13C NMR spectroscopy, i.e. intermolecularly H-bonded homoconjugated anions of acetic, chloroacetic, dichloroacetic, trifluoroacetic, trimethylacetic, and isobutyric acids, and intramolecularly H-bonded hydrogen succinate, hydrogen rac-dimethylsuccinate, hydrogen maleate, and hydrogen phthalate. In particular, primary H/D isotope effects on the hydrogen bond proton signals as well as secondary H/D isotope effects on the 13C signals of the carboxylic groups are reported and analyzed. We demonstrate that in most of the studied systems there is a degenerate proton tautomerism between O-H•••O- and O-•••H-O structures which is fast in the NMR time scale. The stronger is the proton donating ability of the acid, the shorter and more symmetric are the H-bonds in each tautomer of the homoconjugate. For the maleate and phthalate anions exhibiting intramolecular hydrogen bonds, evidence for symmetric single well potentials is obtained. We propose a correlation between H/D isotope effects on carboxylic carbon chemical shifts and the proton transfer coordinate, q1 = 1/2(rOH - rHO), which allows us to estimate the desired OHO hydrogen bond geometries from the observed 13C NMR parameters, taking into account the degenerate proton tautomerism. © 2012 American Chemical Society.

Involved external institutions

Saint Petersburg State University (SPbU) / Санкт-Петербургский государственный университет (СПбГУ) RU Russian Federation (RU) Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie im Forschungsverbund Berlin e.V. / Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy DE Germany (DE) Freie Universität Berlin DE Germany (DE)

How to cite

APA:

Guo, J., Tolstoy, P.M., Koeppe, B., Golubev, N.S., Denisov, G.S., Smirnov, S.N., & Limbach, H.-H. (2012). Hydrogen bond geometries and proton tautomerism of homoconjugated anions of carboxylic acids studied via H/D isotope effects on 13C NMR chemical shifts. Journal of Physical Chemistry A, 116(46), 11180-11188. https://doi.org/10.1021/jp304943h

MLA:

Guo, Jing, et al. "Hydrogen bond geometries and proton tautomerism of homoconjugated anions of carboxylic acids studied via H/D isotope effects on 13C NMR chemical shifts." Journal of Physical Chemistry A 116.46 (2012): 11180-11188.

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