Theoretical Calculation of Separation Factors for Boron Isotopic Exchange between BF₃ and BF₃·C₆H₅OCH₃

Abstract

The separation factors (or equilibrium constants) for boron isotopic exchange reaction (10)BF(3) + (11)BF(3) x C(6)H(5)OCH(3) <==> (11)BF(3) + (10)BF(3) x C(6)H(5)OCH(3) were obtained from MP2/6-31+G(d,p) and B3LYP/6-31+G(d,p) calculations. New scaling factors, single and multiple, were derived from the harmonic frequencies through the least-squares fit for BF(3) and C(6)H(5)OCH(3). The use of multiple scaling factors in the case of C(6)H(5)OCH(3) led to significant improvement in the calculated frequencies over using a single scaling factor. There exists a negligible difference in the separation factors obtained by using the harmonic and the scaled frequencies of the same method, and in those obtained by using different methods. The calculated separation factors for the boron isotopic exchange reaction at 273.15, 293.15, and 298.15K are 1.039, 1.036, and 1.035, respectively, which are in excellent agreement with the experimental values, 1.041 +/- 0.002, 1.030 +/- 0.002, and 1.035 +/- 0.003. This study demonstrated the promise of using DFT (B3LYP) to obtain separation factors for the reactions where the interactions are weaker than covalent bonds but stronger than van der Waals interactions, and consequently to search for better complexation agents than C(6)H(5)OCH(3) for the isotopic separation of BF(3).

Multiple sulfur isotope signatures of sulfite and thiosulfate reduction by the model dissimilatory sulfate-reducer, Desulfovibrio alaskensis str. G20

“…Isotopic equilibrium can be calculated as the reduced partition function ratios of the different isotopologues (Bigeleisen and Mayer, 1947 ; Urey, 1947 ). For partition function calculations, the necessary vibrational frequencies for H 2 S, SO 2− 3 , S 2 O 2− 3 , and SO 2− 4 were obtained by quantum chemical calculations.…”

Effects of Intramolecular Group and Solvent on Vibrational Coupling Modes and Strengths of Fermi Resonances in Aryl Azides: A DFT Study of 4-Azidotolune and 4-Azido-N-Phenylmaleimide

“…Further these convergence criteria have been also used in our previous work on other organic small molecules. [54][55][56][57][58] Anharmonic frequency calculations were performed to understand the origin of FRs and to obtain cubic force constants of overtones and combination bands. Harmonic and anharmonic frequencies of selected normal modes of the two molecules in NNDMA and THF were shown in Tables S1-S4.…”

Metal–organic frameworks (MOFs) as highly efficient agents for boron removal and boron isotope separation

“…2. All seven metal-organic frameworks exhibit higher separation factors than the conventional boron-specic adsorbent Amberlite IRA-743 (1.022) 45 and isotopic exchange distillation factors (1.039) 6 . Among them, MIL-101(Cr) and MIL-100(Fe) exhibit boron isotope separation factors of 2.00 and 1.75, respectively.…”

“…3 Although methods for boron isotope separation are in high demand for the nuclear power industry and medical treatment, the separation process is practically very difficult because of the tiny differences between its isotopes. Some methods have been observed including exchange distillation, [4][5][6] adsorption-based separation, [7][8][9][10][11][12][13][14][15] thermal ionization mass spectrometry 16,17 and the laser assisted retardation of condensation (SILARC) method, [18][19][20][21][22][23][24] among which only isotopic exchange distillation has been successfully applied in practical 10 B production. 4 Except for a small separation factor of around 1.03, disadvantages including the instability of the anisoleboron triuoride complex, severe causticity to the equipment and insecurity as a result of the toxicity of boron triuoride greatly impede the process.…”