Knowledge Bank

The microwave spectrum of isobutylene has been studied in the range from 19--33 kmc, and a number of rotational transitions have been identified. The pattern of the low-J transitions is that of an effective rigid rotor with the constants $ao=9133.32$ Mc, $bo=8381.61$, $co=4615.99$. Certain high-J lines are split into triplets by the internal rotation of the two methyl groups. A preliminary analysis of these splittings implies an internal barrier of 2.3 kcal/mole.