The microwave, Raman, far infrared, and NMR spectra and structure of methylchloroformate

Abstract The microwave spectra of six isotopic species of methylchloroformate, ClCO 2 CH 3 , have been recorded from 18.0 to 40.0 GHz. Structural parameters have been determined, and it is shown that the only stable conformer at ambient temperature is the s-trans . The Raman and far infrared spectra of the vapor are reported. Four cases of Fermi resonance have been observed in the Raman effect. Both the methyl and methoxy torsions have been observed in the far infrared, and the methyl barrier to internal rotation has been determined to be 1.15 kcal/mole (1.19 kcal/mole for the CD 3 rotor), which is in agreement with the 1.23 kcal/mole obtained from the microwave splitting method. It is shown from both the 13 C and 1 H NMR spectra along with the far-infrared data that only one conformer exists, which is contrary to what was previously reported. The vibrational spectrum of the solid is also reported and discussed.