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An ab initio study of the geometry and energy of six planar conformers of β‐hydroxyacrolein
Author(s) -
George Phillip,
Bock Charles W.,
Trachtman Mendel
Publication year - 1980
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.540010409
Subject(s) - conformational isomerism , ab initio , basis set , chemistry , geometry , energy minimization , crystallography , isomerization , molecular geometry , bond length , hydrogen bond , delocalized electron , ab initio quantum chemistry methods , computational chemistry , molecule , crystal structure , density functional theory , mathematics , biochemistry , organic chemistry , catalysis
Ab initio calculations with full geometry optimization have been carried out on the planar cCc , cTc , tTc , tCt , tTt , and cCt conformers of β‐hydroxyacrolein using the 4‐21G basis set, and on the cCc and cCt conformers using the 4‐31G basis set. The hydrogen‐bonded cCc conformer is the most stable and the cCt conformer the least stable, with the other conformers following the above sequence. β‐Hydroxy substitution has scarcely any influence on the geometry of the trans ‐acrolein structure, whereas the geometry of the cis ‐acrolein structure shows significant changes which depend on whether the OH group is cis or trans with respect to the CHO group about the CC bond. The Δ E T values for cis → trans isomerization about the CC bond in cCt and cTc support the hypothesis that these changes in geometry are the result of a destabilizing interaction in cCt and a stabilizing interaction in cTc. The geometry of the hydrogen‐bonded structure cCc sets it apart from all the other conformers: it has by far the longest CC, the longest CO, the longest OH, the shortest CC, and the shortest CO. Its formation from cCt involves a lengthening of CC, CO, and OH and a shortening of CC and CO, indicating a delocalization of charge within the ring. 4‐21G calculations have also been made for a distorted cCt structure that has the same bond lengths and angles as the equilibrium cCc structure, and the distortion energy, cCt (equm. geom.) → cCt (distorted geom.), is found to be +13.1 kJ mole −1 . Taking the energy of this distorted cCt structure as the baseline, the hydrogen‐bonding energy in cCc is found to be —80.3 kJ mole −1 .