The Boron Trifluoride/Nitromethane Ratio of the BF₃·CH₃NO₂ Adduct
In recent years the boron trifluoride-nitromethane adduct has received attention in a number of different fields. It functions as a catalyst in cyclization reactions, in substitutional reactions involving the cracking of ring compounds, and in the creation of stereospecifically pure enantiomers. It has also been suggested as an effective means of separating the isotopes of boron. In all of the research involving this adduct, the ratio of BF3 to nitromethane has been assumed to be somewhere in the range of 1.4/1 to 1.6/1, as reported by Herbst. However, the present study has found the ratio to be significantly lower, 0.158/1. This ratio was obtained by reacting dilute solutions of the adduct with water and titrating the resulting hydrofluoric acid. Gravimetric analysis obtained a very similar result. An independent confirmation was made by the Eagle Picher Boron Laboratory where the adduct was titrated for total boron, and the same ratio was found. A pilot plant was constructed to investigate commercial use of the adduct, and the ratio of 0.158/1 was also confirmed there. Based on this ratio, the heat of association was calculated to be -8.51 kJ/mol. The specific heat was measured to be 0.52 cal/g⁰C, and the room temperature density was determined to be 1.31 g/cm3.
B. T. Eldred et al., "The Boron Trifluoride/Nitromethane Ratio of the BF₃·CH₃NO₂ Adduct," Separation Science and Technology, vol. 35, no. 6, pp. 931-940, Taylor & Francis, Jan 2000.
The definitive version is available at http://dx.doi.org/10.1081/SS-100100202
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