Remarkable shifts of C sp2 -H and O-H stretching frequencies and stability of complexes of formic acid with formaldehydes and thioformaldehydes.

Autor: Trung NT; Laboratory of Computational Chemistry and Modelling, and Department of Chemistry, Quy Nhon University, Quy Nhon, Vietnam., Khanh PN; Laboratory of Computational Chemistry and Modelling, and Department of Chemistry, Quy Nhon University, Quy Nhon, Vietnam., Carvalho AJP; Department of Chemistry, School of Sciences and Technology, and Évora Chemistry Center, IIFA, University of Évora, Évora, Portugal., Nguyen MT; Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium.
Jazyk: angličtina
Zdroj: Journal of computational chemistry [J Comput Chem] 2019 May 15; Vol. 40 (13), pp. 1387-1400. Date of Electronic Publication: 2019 Feb 04.
DOI: 10.1002/jcc.25793
Abstrakt: Thirty-six stable complexes of formic acid with formaldehydes and thioformaldehydes were determined on the potential energy surface, in which the XCHO···HCOOH complexes are found to be more stable than the XCHS···HCOOH counterparts, with X = H, F, Cl, Br, CH 3 , NH 2 . All complexes are stabilized by hydrogen bonds, and their contribution to the total stabilization energy of the complexes increases in going from C-H···S to C-H···O to O-H···S and finally to O-H···O. Remarkably, a significant blueshift of C sp2 -H bond by 81-96 cm -1 in the C sp2 -H···O hydrogen bond has hardly ever been reported, and a considerable redshift of O-H stretching frequency by 206-544 cm -1 in the O-H···O/S hydrogen bonds is also predicted. The obtained results in our present work and previous literatures support that a distance contraction and a stretching frequency blueshift of C-H bond involving hydrogen bond depend mainly on its polarity and gas phase basicity of proton acceptor, besides the rearrangement of electron density due to complex formation. Markedly, we suggest the ratio of deprotonation enthalpy to proton affinity (R c ) as an indicator to prospect for classification of hydrogen bonds. The symmetry adapted perturbation theory results show a larger role of attractive electrostatic term in XO-n as compared to that in XS-n and the electrostatic interaction is overwhelming dispersion or induction counterparts in stabilizing XO-n and XS-n, with n = 1, 2, 3. © 2019 Wiley Periodicals, Inc.
(© 2019 Wiley Periodicals, Inc.)
Databáze: MEDLINE
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