The vibrational spectra and rotational isomerism of monochloromethyl acetate and methyl oxalyl chloride

The IR spectra of monochloromethyl acetate and methyl oxalyl chloride have been studied for the vapour, liquid and solid states. For the first ester only one conformation is present and it has a planar arrangement of heavy atoms with the chlorine directed away from the carbonyl group and with a s-cis arrangement for the basic ester framework. For methyl oxalyl chloride, evidence is presented for the presence of two rotamers, the more stable of which is probably planar with a trans arrangement of carbonyl groups.