Microwave spectrum, centrifugal distortion, dipole moment and conformation of 2-methyl-1,3-dioxane

Microwave spectrum of 2-methyl-1,3-dioxane has been investigated in the frequency range 8–40 GHz. Rotational a-type and c-type transitions with J≤40 have been identified. Rotational constants A = 4658.122(2) MHz, B = 2503.221(1) MHz, C = 1783.950(1) MHz and centrifugal distortion constants for the ground vibrational state have been found. Dipole moment components µ_a = 1.43 ± 0.01 D, µ_c = 1.15±0.01 D and overall dipole moment µ = 1.84±0.02 D have been determined. The data obtained are in accord with the chair conformation of the molecule having equatorial arrangement of the methyl group.