Microwave spectrum of axial cyclohexyl chloride and conformational equilibrium in cyclohexyl chloride

The high-resolution microwave spectrum of the axial conformer of cyclohexyl chloride has been assigned for both the Cl(35) and Cl(37) isotopic species, in natural abundance. Moreover, the high-resolution microwave spectrum of the equatorial conformer, previously assigned in the ground state [ Chem. Phys. Lett. 21 , 592–594 (1973)], has been further investigated. Several low-energy vibrational satellites have been studied for the Cl(35) isotopic species of both the axial and the equatorial isomers. The ground state centrifugal distortion constants for both the isotopic species of the two rotamers, and the quadrupole coupling constants of Cl(35) and Cl(37) axial isomer and of Cl(37) equatorial isomer (not reported previously) have been determined. From line relative intensity measurements the energy difference between the two conformers has been calculated to be 0.51 ± 0.15 kcal/mol, the equatorial isomer being more stable. In the same way, the vibrational energies of the investigated vibrational satellites have been computed. A structural model for axial cyclohexyl chloride is proposed on the basis of the available experimental data.