MICROWAVE SPECTRUM,CONFORMATION,BARRIER TO INTERNAL ROTATlON, CENTRIFUGAL DISTORTION, AND DIPOLE MOMENTOF

The microwavespectrumof methylpropargylether,CH3OCH2C=CH,hasbeen investigatedin the11.9-26.5 GHz region.Only thegaucherotamerwith adihedral angleof 68o:t 2o fromthesynpositionwasassigned.Otherformsarenot presentin concentrations exceeding 10 % of the total. The barrier to internal rotation of the methyl group was determinedto be 2512:t 75 cal mol-I. The dipole moment components are /la =0.290:t 0.003D, /lb =0.505:t 0.012 D, and /le =1.016:t 0.003 D. The total dipole moment is 1.171:t 0.013 D. Extensive centrifugal distortion analyseshave beencarried out for the ground as well as for two vibrationally excited states. For the ground state, transitions up to J = 77 were assignedand a largecentrifugal distortion exceeding9 GHz enabled the determination of accurate quartic and significant sextic distortion coefficients