The infrared spectra of a number of malonates and oxalates (as liquid films) were examined at various temperatures and narrower slit widths than had previously been used. The absorption in the 5.8 μ region is very complex, at least four bands being observed in each case. Small but definite temperature effects were recorded for both types of esters. At somewhat wider slit widths only two bands were observed, these occasionally having indistinct shoulders. The spectra of some of the compounds were also measured in both carbon tetrachloride and acetonitrile solutions (two bands observed in each case) and the ratios of the intensities of the two bands compared. A possible explanation of the effects observed is that at least two rotational isomers can exist for each compound and that vibrational coupling of the carbonyl stretching frequencies can occur in each of the rotational isomers.
