Abstract
Pentaerythritol, C(CH2OH)4, a crystalline alcohol, and diketopiperazine, (CH2NHCO)2, also crystalline, have been subjected to an infra-red absorption study with plane polarized waves in the region 1–2.5μ. Pronounced pleochroism is observed, and this dependence of absorption upon the plane of vibration of the electric vector, E0, is used in identifying the bands associated with the normal vibrations of the methylene groups, CH2, in each crystal. An interesting example of Fermi resonance arises. In pentaerythritol the appearance of pronounced absorption by perturbed OH groups when E0 oscillates along the c axis indicates that the feature of the crystalline structure, deduced from an x-ray diffraction study which orients all of the OH groups at right angles to this axis, must be modified. The absence of the usual NH absorption near 1.50μ supports Corey's assumption of electron resonance in diketopiperazine.

This publication has 11 references indexed in Scilit: