Fourier transform microwave study on 2-methyloxetane and 3-methyloxetane

The rotational spectra of 2-methyloxetane and 3-methyloxetane have been reinvestigated using Fourier transform microwave spectroscopy (FTMW). A,E splittings due to internal rotation of the methyl group have been observed in the ground and several ring-puckering and methyl torsion excited states for both molecules. Internal rotation barriers of V-3 = 3.332(14) kcal mol(-1) (13.941(58) kJ mol(-1)) for 2-methyloxetane and V-3 = 3.284(12) kcal mol(-1) (13.740(50) kJ mol(-1)) for 3-methyloxetane have been determined from the ground vibrational state spectra. Furthermore, the rotational, quartic and some higher-order centrifugal distortion constants are reported. The experimental set-up of a waveguide Fourier transform microwave spectrometer is also presented.