Methyl Internal Rotation in the Microwave Spectrum of o-Methyl Anisole

International audienceThe microwave spectrum of o‐methyl anisole (2‐methoxytoluene), CH3OC6H4CH3, has been measured by using a pulsed molecular jet Fourier transform microwave spectrometer operating in the frequency range 2–26.5 GHz. Conformational analysis using quantum chemical calculations at the MP2/6–311++G(d,p) level of theory yields only one stable conformer with a Cs structure, which was assigned in the experimental spectrum. A–E splittings due to the internal rotation of the ring methyl group could be resolved and the barrier to internal rotation was determined to be 444.05(41) cm−1. The experimentally deduced molecular parameters such as rotational and centrifugal distortion constants as well as the torsional barrier of the ring methyl group are in agreement with the calculated values