Microwave spectrum of 2,6-dimethylcyclohexanone

• Published in: Journal of molecular spectroscopy Vol. 337; pp. 65 - 71
• Main Authors: Jang, Heesu, Shim, Jae-Seol, Oh, Jung Jin
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-07-2017
• Subjects: 2,6-Dimethylcyclohexanone; Conformational analysis; Dipole moments; Rotational spectrum; Rotational spectrum; Dipole moments; 2,6-Dimethylcyclohexanone; Conformational analysis
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/j.jms.2017.04.021

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•Microwave spectra for two (ee and ea) conformers were measured.•Rotational and centrifugal distortion constants of 2,6-DMCHO were determined.•Ab initio structures were compared with those of substituted cyclohexanone.•Dipole moments were derived from Stark effect coefficients.
The rotational spectrum of 2,6-dimethylcyclohexanone (DMCHO) was measured in the frequency region from 6 to 12GHz. 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, ΔJ = 0.086(11)kHz, ΔJK=−0.134(20)kHz, ΔK=0.298(15)kHz, δJ = 23.4(24)Hz, and δK=101.4(77)Hz; and (ea) A=2082.62538(83)MHz, B=1566.59564(59)MHz, C=1113.90153(75)MHz, ΔJ = 0.066(23)kHz. In addition, dipole moment components of the two isomers were determined by Stark effect measurements: (ee) μb=2.6673(12) D, μc=1.0379(11) D, μtotal=2.8621(12) D; and (ea) μa=1.385(253) D, μb=2.358(104) D, μc=1.172(21) D, μtotal=2.975(144) D. Ab initio calculations for all three isomers were compared with each other and with experimental results.