Microwave Spectra of Molecules Exhibiting Internal Rotation. II. Methylallene

Abstract
The microwave spectrum of methylallene, CH3CH:C:CH2, has been investigated in the region 16–33 kmc, and the J=1→2, 2→3, and 3→4 transitions measured. Most of the observed lines are split slightly as a result of internal rotation. Analysis of the splittings by the methods of Hecht and Dennison leads to an internal potential barrier of 556.0±2 cm—1 or 1589±6 cal/mole. The principal moments of inertia (in units of amu A2) are 14.93, 120.321, and 128.713. The electric dipole moment is 0.401 D and makes an angle of 10°8′ with the a principal axis.