Shrinkage Effect by Thermal Vibrations in Linear-Skeleton Molecules

Apparent shrinkages of the interatomic distances along the carbon-carbon chains in allene and dimethyl-diacetylene are calculated from spectroscopic data. The L—1 matrices obtained from a normal coordinate analysis are used to calculate the perpendicular mean-square amplitudes of vibration from which the shrinkages are obtained. The computed values of the shrinkages are in fairly good agreement with those obtained from electron diffraction investigations.