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Three conformers observed and characterized in 1‐hexyne
Author(s) -
Atticks Karissa,
Bohn Robert K.,
Michels H. Harvey
Publication year - 2001
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.1531
Subject(s) - conformational isomerism , chemistry , ab initio , acetylene , electronic correlation , computational chemistry , ab initio quantum chemistry methods , gauche effect , crystallography , molecule , organic chemistry , medicine , surgery
Abstract The microwave spectrum of 1‐hexyne ( n ‐butyl acetylene) reveals the presence of three conformers that have been carefully characterized. 1‐Hexyne can be viewed as propane with terminal ethynyl and methyl substituents. These substituents can be arranged in anti–anti (AA), anti–gauche (AG), gauche–anti (GA), gauche–gauche (GG cis), and gauche–gauche′ (GG trans) conformations. The first three conformers are those observed experimentally and their rotational constants have been determined. The GG conformers, in both cis and trans arrangements have not been positively identified to date. We have determined the structural parameters and energies of all five possible conformations through ab initio quantum mechanical calculations at the HF, MP2, and B3LYP levels of theory. The calculated energies of these five conformers are very close, and a change in the relative stability of these conformers is found at different levels of theory. We find that inclusion of electron correlation effects is critical to our understanding of the energy ordering of these conformers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001