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Ab initio molecular orbital studies of sigmatropic rearrangements
Author(s) -
Bouma Willem J.,
Vincent Mark A.,
Radom Leo
Publication year - 1978
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560140609
Subject(s) - ab initio , chemistry , molecular orbital , degenerate energy levels , sigmatropic reaction , computational chemistry , propene , formic acid , atomic orbital , transition state , molecular orbital theory , stereochemistry , physics , molecule , catalysis , quantum mechanics , organic chemistry , electron
Ab initio molecular‐orbital theory with the STO ‐3G and 4‐31 G basis sets has been used to study the 1,3‐sigmatropic hydrogen rearrangements: propene→propene, formic acid→formic acid, and vinyl alcohol→acetaldehyde, and the1,5‐shifts:1,3‐pentadiene→ 1,3‐pentadiene and β‐hydroxyacrolein→ β‐hydroxyacrolein. Transition states have been determined using gradient procedures. Improved descriptions of the energies of the reactions have been obtained using 3 × 3 configuration interaction. In accord with expectations based on orbital‐symmetry considerations, the calculated barriers are considerably greater for 1,3‐ than for 1,5‐shifts. The forbidden pathway for the degenerate 1,3‐shift in propene is predicted to require less activation energy than the allowed pathway, a result that can be rationalized in terms of interactions with subjacent and superjacent orbitals.