Far infrared spectra of methyl nitrate and methyl-d 3 nitrate

Abstract

The far infrared spectra from 300 to 50 cm −1 of methyl nitrate, CH 3ONO 2, and methyl-d 3 nitrate, CD 3NO 2, have been recorded at a resolution of 0.12 cm −1. The fundamental methyl torsional mode has been observed at 204.5 cm −1 (154.2 cm −1 for CD 3ONO 2) with two excited states falling to lower frequencies which gives a V 3 barrier of 980 ± 40 cm −1 (2.80 ± 0.11 kcal/mol). The NO 2 torsion (methoxy) has been observed with the 1 ← 0 transition being at 133.7 cm −1 (119.5 cm −1 for CD 3ONO 2) and eight successive excited states falling to lower frequencies. From these data the twofold barrier to internal rotation has been calculated to be 2650 ± 75 cm −1 (7.69 ± 0.21 kcal/mol).