The infrared spectra of liquid and solid films of
formaldehyde were taken over the range of 35 to 4,000 cm⁻¹
using Beckman IR 7 and IR 11 spectrometers. A new overtone
band and a new combination band were found as well as three
fundamental peaks due to lattice vibrations and several peaks
arising from combinations of internal and external modes
of vibration. The peak at 180-195 cm⁻¹ is very strong and
appears to be due to libration of the formaldehyde molecule
about the principal axes perpendicular to the axis of the
carbon-oxygen bond. The considerably weaker peaks appearing
at 60 and 100 cm⁻¹ probably are due to rotation about the
axis of the carbon-oxygen bond and to translation. The spectrum
obtained in the near infrared region is essentially the same
as the spectrum reported by Harvey and Ogilvie. The frequency
shifts of the peaks for different states of condensation
indicate that hydrogen bonding does not occur in the liquid
or solid and that the intermolecular binding forces are due
largely to dipole-dipole interactions
