The Microwave Spectra of m-Xylene and m-Xylene-d10. Determination of the Low Methyl Internal Rotation Barrier
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چکیده
The rotational spectra of m-xylene, (CH3)2C6H4, and of m-xylene-d10, (CD3)2C6D4, have been recorded between 6 and 26.5 GHz using pulsed beam Fourier transform microwave spectroscopy. The clue for the assignment of the internal rotation multiplets was the inertial defect derived from the A1A1 species transitions. The rotational constants for m-xylene and m-xylene-d10 are A = 3572.1117(1) MHz / 2896.1195(17) MHz, B = 1761.8621(1) MHz / 1446.0236(15) MHz, C =1197.3943(2) MHz / 988.2357(7) MHz, the barrier to internal rotation of the two methyl groups are V3 = 53:7(16) J/mol / 39.8(5) J/mol, their moments of inertia were assumed to be I = 3.14 uÅ / 6.28 uÅ.
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