Microwave spectrum of 2,6-dimethylcyclohexanone

Abstract

The rotational spectrum of 2,6-dimethylcyclohexanone (DMCHO) was measured in the frequency region from 6 to 12 GHz. Among three possible conformational isomers, two conformers were identified where two methyl groups are aligned in the equatorial/equatorial (ee) and the equatorial/axial (ea) positions. Both b-type and c-type transitions for (e,e)-2,6-DMCHO, and a-type, b-type, and c-type transitions for (e,a)-2,6-DMCHO were assigned to determine the rotational constants and quartic centrifugal distortion constants based on the Watson-A reduction Hamiltonian: (ee) A = 2150.95789(48) MHz, B = 1578.76212 (40) MHz, C = 990.19141(45) MHz, Delta(j) = 0.086(11) kHz, Delta(JK) = -0.134(20) kHz, Delta(K) = 0.298(15) kHz, delta(J) = 23.4(24) Hz, and delta(K) = 101.4(77) Hz; and (ea) A = 2082.62538(83) MHz, B = 1566.59564(59) MHz, C = 1113.90153(75) MHz, 41 = 0.066(23) kHz. In addition, dipole moment components of the two isomers were determined by Stark effect measurements: (ee) mu(b) = 2.6673(12) D, mu(c)= 1.0379(11) D, mu(total) = 2.8621 (12) D; and (ea) mu(a) = 1.385(253) D, mu(b) = 2.358(104) 0, mu(c) = 1.172(21) D, mu(total) = 2.975(144) D. Ab initio calculations for all three isomers were compared with each other and with experimental results. (C) 2017 Elsevier Inc. All rights reserved.