Mass Spectrometric Study of the Reactions of BF3(g) with BCl3(g), B(OH)3(g), and B2O3(1)

Exchange reactions of halogen and hydroxyl with BX3(g) have been studied mass spectrometrically. The major product produced by the reaction of BF3(g) with boric acid at 25°C and pressures of the order of 10—6 atm is B(OH)F2(g). The species B(OH)2F(g) is also formed at higher temperatures when B(OH)3(g) is observable. Equilibria involving the reactions13BF3(g)+23BCl3(g)=BFCl2(g),23BF3(g)+13BCl3(g)=BF2Cl(g),13BF3(g)+23B(OH)3(g)=B(OH)2F(g),and 23BF3(g)+13B(OH)3(g)=B(OH)F2(g),have been studied as a function of temperature. Heats of formation at 298°K for BFCl2(g), BF2Cl(g), B(OH)2F(g), and B(OH)F2(g) are found to be —154.1±1.0, —211.9±2.0, —249.8±2.5, and —260.2±2.5 kcal/mole, respectively. Reactions of BF3(g) with B2O3(l) have also been studied at pressures between 10—6 and 10—3 atm and temperatures between 400 and 1000°K. Results are consistent with published data from studies with BF3 at pressures near 1 atm and show that (BOF)3(g) is the primary product at both pressure extremities. For the reactionBF3(g)+B2O3(l)=(BOF)3(g),we obtain ΔHT°=3.46±0.30 kcal/mole.