Normal Coordinate Analyses of Hydrogen-Bonded Compounds. III. The Acid Maleate Ion

The infrared spectra of the acid maleate ion and its two deutero analogs have been obtained from 4000 to 160 cm−1. In order to estimate the Urey—Bradley force constants, a normal coordinate analysis has been carried out on the C2v model of the acid maleate ion. The antisymmetric and symmetric O–H–O stretching and O–H–O bending bands have been assigned at 2008, 310, and 1700 cm−1, respectively. The O–H–O stretching and bending force constants used are 1.10 and 0.60 mdyn/Å, respectively. Calculations of potential-energy distribution reveal that strong vibrational coupling makes it virtually impossible to assign group frequencies in the low-frequency region.