Internal rotation and the chlorine nuclear quadrupole coupling tensor of 1-chloropropane

The rotational spectra of the trans and gauche forms of 1-chloropropane have been analyzed in the frequency range 8-40 GHz using Stark, waveguide FTMW, and pulsed molecular beam FTMW spectrometers. The spectra of Cl-35, Cl-37, and the three C-13 isotopomers have been observed for both conformers. The complete quadrupole Cl-coupling tensors have been determined and discussed within the structural considerations. For the gauche form the barrier to internal rotation of the methyl group has been determined to be 2908(4) cal/mol from A-E splittings observed in the first excited torsional state. Two A-E splittings have been observed only in the ground state of the trans form. From these splittings a barrier of 2760 cal/mol has been estimated. (C) 1997 Academic Press.