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Non‐planar structures of the pentafluoroallyl and 1,1‐difluoroallyl anions
Author(s) -
Dixon David A.,
Fukunaga Tadamichi,
Smart Bruce E.
Publication year - 1988
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.610010305
Subject(s) - chemistry , carbanion , basis set , ion , planar , computational chemistry , crystallography , molecule , potential energy surface , stereochemistry , density functional theory , organic chemistry , computer graphics (images) , computer science
The structures of the allyl anion ( 1 ) and two fluoro‐substituted derivatives, perfluoro ( 2 ) and 1,1‐difluoro ( 3 ) have been calculated by ab inito molecular orbital theory. Geometries were gradient optimized, and force fields and an MP‐2 correlation correction were determined at stationary points. The calculations were done with a double zeta basis set augmented by d functions on carbon (DZ + D c ). Final self‐consistent field (SCF) and MP‐2 energy calculations were done with the DZ + D c basis set augmented by diffuse functions. The ground state of 1 is the planar allyl anion (C 2v ). The rotation barrier in 1 is 21·1 kcal/mol at the MP‐2 level. The cyclopropyl carbanion is 27·0 kcal/mol higher in energy at the MP‐2 level. The perfluoroallyl anion is not planar, and the rotated structure is 25·7 kcal/mol more stable than the C 2v structure at the MP‐2 level. The lowest energy structure on the potential energy surface for 2 is the perfluorocyclopropyl carbanion which is 27·8 kcal/mol more stable than the C 2v structure at the MP‐2 level. The 1,1‐difluoroallyl anion is also not planar. Here the most stable structure on the potential energy surface is the rotated allyl anion which is 8·3 kcal/mol more stable than the all‐planar allyl anion structure.