Quantum Chemical Study of the Phosphite-Phosphonate Tautomerization: Applications to bis(2-Ethylhexyl) Phosphonate (BIS) and Other Simulants for Chemical Warfare Agents
Abstract
Quantum chemical methods (ab initio, semiempirical, and Hartree-Fock) were used to calculate the energy of several phosphite-phosphonate tautomers, and thereby determine the position of equilibrium in the gas phase. Unless the phosphorus moiety contains significant electron withdrawing groups, the equilibrium lies far toward the phosphonate. None of the methods consistently produced thermodynamic values that agreed within 5 kcal/mole. In the most stable conformation of trimethyl phosphite, two of the methoxy ligands were oriented upward (with respect to the lone pair) in a pseudocistoid or gauch arrangement and the other pointed downward in a transoid orientation. Dimethylmethyl phosphonate (DMMP) had a similar structure. The methyl group assumed the Trans position, and the two methoxy were in the gauch. The two long alkyl chains in BIS were oriented in a V fashion with the ends on the molecule about 14 angstroms apart. The vibrational spectra for trimethyl phosphite, DMMP, and bis(2-ethylhexyl) phosphonate were calculated at the HF/6-3 11 G** level and compared to experimentally measured frequencies. Graphic representations of the calculated vibrations and correlation with traditional group frequencies were used to make the individual assignments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2002
- Accession Number
- ADA410497
Entities
People
- William E. White
Organizations
- Edgewood Chemical Biological Center