Anomalous Behavior of 18O-Labeled Compounds. VI. The Vibrational Spectra of Isotopic Metaborates

The infrared absorption spectrum of an aqueous solution of 18O-labeled sodium metaborate shows the antisymmetric B–18O stretching ν3 fundamental of its B(OH)4− ions at 982 cm−1, as compared with the frequency of 958 cm−1 observed for the respective normal borate vibration. The Raman spectrum of aqueous solutions of these borates exhibits their symmetric B–O stretching ν1 fundamental in both cases at 744 cm−1. The fact that the ν1 and ν3 frequencies of the hydrated B(18OH)4− ions are not decreased by the 16O–18O exchange is taken to indicate that the hydrogen bonding between the B(OH)4− ions and their solvating water molecules is appreciably lower in the case of the 18O-labeled ions than in the case of the B(16OH)4− ions.