Rotational Spectra of Seven Conformational Isomers of 1-Hexene

Published

February 1, 2000

Author(s)

Gerald T. Fraser, R D. Suenram, C Lugez

Abstract

The rotational spectra of 7 of the expected 13 conformational isomers of 1-hexene have been measured and assigned at a rotational temperature of 1 symmetry, as verified by the observation of a, b, and c-type electric-dipole transitions. The remaining conformer has C_s symmetry, consistent with its small inertial defect, {Δ}{identical with} I_cc - I_bb - I_aa = -12.65 u ², and the observation of only a and b-type transitions. Here, Iaa is the moment of inertia of the conformer about its α-principal axis. The inertial defects determined for the seven conformers range from -12.65 u ² to -51.29 u ². Both the molecular mechanics and ab initio calculations indicate the observed conformers are associated with the seven lowest energy conformational minima of 1-hexene. The ab-initio-calculated energy difference between the lowest and highest energy conformers observed is 326 cm^-1, including vibrational zero-point contributions, indicating that the conformational temperature is not equilibrated with the approximately 2 K rotational temperature of the molecular-beam expansion.

Citation

Journal of Physical Chemistry A

Volume

104

Issue

No. 6

Pub Type

Journals

Keywords

computational chemistry, conformer, hexene, microwave spectroscopy, molecular beam spectroscopy, molecular modeling, rotational spectroscopy

Citation

Fraser, G. , Suenram, R. and Lugez, C. (2000), Rotational Spectra of Seven Conformational Isomers of 1-Hexene, Journal of Physical Chemistry A (Accessed October 12, 2025)