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A comparison of selected force constants derived from ab initio SCF calculations on β‐hydroxyacrolein. Acrolein, performic acid, and formic acid
Author(s) -
Bock Charles W.,
Trachtman Mendel,
George Philip
Publication year - 1981
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540020208
Subject(s) - conformational isomerism , performic acid , chemistry , hydrogen bond , formic acid , intramolecular force , crystallography , mndo , ring (chemistry) , molecule , equilibrium constant , computational chemistry , stereochemistry , organic chemistry
Abstract Harmonic force fields have been calculated for the planar hydrogen‐bonded ring conformer of β‐hydroxyacrolein, c C c , which is the most stable, and the chain conformer, c C t , generated by 180° rotation of OH about the CO bond axis. The equilibrium structure obtained using the 4‐31 G basis set with full geometry optimization was employed in each case. Selected force constants for the bonds directly concerned in the formation of the ring from the chain structure, and the increments in going from the one to the other, are compared with the values for the corresponding conformers of performic and formic acids. As the ring size increases from four in trans ‐formic acid, to five in cis – cis ‐performic acid and to six in the c C c conformer of β‐hydroxyacrolein there is a successive increase in the mechanical strength of the hydrogen‐bridging unit. The energy changes for the chain → ring conversion do not follow this progression: performic acid is out of order. But, since a force constant is a localized bond property, whereas the energy changes are determined not only by interactions specific to the hydrogendonor and hydrogen‐acceptor groups but also by interactions involving more distant parts of the molecule, the force constants for the bonds directly concerned in the formation of the hydrogen bridge provide a less ambiguous basis for comparing the strength of the intramolecular hydrogen bonding.