Order-disorder transitions in 2,3-benzothiophene and cyclopentyl-
1-thiaethane as well as the vibronic effects in the phase
transitions of the alkali metal salts of TCNQ have been investigated
by infrared spectroscopy. In all these cases, marked variations in
band intensities accompany the transitions. Existence of two crystalline
forms of methylcyclohexane has been established by infrared
spectroscopy. Phase transitions of aliphatic dicarboxylic
acids have been examined with particular attention to the transiti_
ons in malonic, succinic, and glutaric acids