INFRARED SPECTRA OF MATRIX ISOLATED $B(OH)_{3}$. HOBO AND $(HOBO)_{3}$.
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Date
1967
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Ohio State University
Abstract
Infrared spectra of $B(OH)_{3}, HOBO$ and $(HOBO)_{3}$ have been obtained in neon, argon and nitrogen matrices near $4^{\circ} K$ over the region $250-4000 cm^{-1}$. The various isotopically enriched molecules containing $B^{10}(96.3\%), B^{11}(98.3\%)$ and $H^{2}(99.7\%)$ have also been studied. The metaboric acid monomer molecules were generated by the reaction $B_{2}O_{3} (1)+H_{2}O\rightleftarrows 2HOBO$ (g) at temperatures near $1400^{\circ} K$. The fundamental vibrations have been assigned assuming $C_{****}$ symmetry (linear heavy atom array). Force constants and thermodynamic functions have been calculated and will be discussed. The orthoboric acid monomer molecules were generated by the reaction: $B(OH)_{3} (C) \stackrel{\Delta}{\longrightarrow} B(OH)_{3} (g)$ at $293^{\circ} K$. The infrared active modes of all the isotopic species have been carefully measured. Values for the infrared inactive modes were obtained by studying the mixed $[B(OH)(OD)_{2}$ and $B(OH)_{2}(OD)]$ molecules and applying an isotopic correction factor. Force constants and thermodynamic functions have been calculated. The hydrogen frequency differences between isolated and crystalline boric acid, ca. $400 cm^{-1}$ for the stretching and ca. $200 cm^{-1}$ for the bending modes, suggest moderately strong hydrogen bonds in the crystal. Trimeric metaboric acid was produced via vaporization of the crystalline material: $(HOBO)_{3} (c) \stackrel{\Delta}{\longrightarrow} (HOBO)_{3} (g)$ near $440^{\circ} K$. A qualitative assignment of the infrared data has been made and interpretation of the results will be discussed.
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Author Institution: Research Department Physics Division, Naval Ordnance Station, Indian Head, Maryland, 20640