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

Abstract

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 C_2v 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.