Premium
Substituent effects on the conformational stability of allyl fluorides
Author(s) -
Qiu Yongge,
Han Daxiong
Publication year - 2011
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1777
Subject(s) - conformational isomerism , substituent , chemistry , vicinal , stereochemistry , enthalpy , cis–trans isomerism , crystallography , hyperconjugation , molecule , computational chemistry , thermodynamics , organic chemistry , physics
By the B3P86/6‐311G(3d,2p) method, remote substituent effects on trans ‐YCHCHCH 2 F were investigated by examining their conformational stabilities, molecular geometries, and stereoelectronic interactions in this paper. The cis conformer is favored for YH, Cl, Me, Vinyl, CF 3 , CN, CHO, and NO 2 , whereas the gauche is favored for YOMe, OH. A correlation of Δ H with the substituent constants σ + (Y) shows that the increasing electron‐withdrawing ability of the substituent Y increases the relative stability of the cis conformer. It was found that the substituent effect on the molecule stabilization energies (relative to CH 2 CHCH 2 F) is more significant in the gauche conformers than in the cis conformers. In agreement, molecular structures of the gauche conformers were also observed to vary more significantly with the substitution than those of the cis conformers. By the second‐order perturbation energy ( E (2)) in NBO analysis, it was found that the total C 2 –C 3 vicinal hyperconjugation is determinant in the enthalpy difference and consequently controls the conformational stability. Further analysis shows that the substituent effect on the C 2 –C 3 vicinal hyperconjugations is much higher in the gauche conformers than in the cis conformers. The highly sensitive π CC →σ* CF interaction to the substitution in the gauche conformers, is the leading factor in variation of molecular stability and geometry. Copyright © 2010 John Wiley & Sons, Ltd.