Electronic structure and conformational properties of vinylphosphonic acid and some related derivatives

Abstract

The electronic structure and conformational properties of vinylphosphonic acid, vinylphosphoryl dichloride, and vinylphosphine oxide have been studied by ab initio quantum mechanical methods. Furthermore, the vinylphosphonic acid has been studied experimentally by means of 13C N M R and ultraviolet spectroscopy. This compound has been synthesized by a modification of the McKenna hydrolysis reaction, improving significantly the yield. The ab initio calculations have been performed with different basis sets, including correlation energy a t the MP2/6-31G* level. Topological analysis of charge density has also been carried out. Two conformers, s-cis and s-trans-gauche, have been determined for the internal rotation around the C-P bond, with low rotational barriers. Two transition structures, s-cis-gauche and s-trans, have been located. A partially polarized strong triple bond for the phosphoryl group has been found. A weak ?r conjugation has been detected in the C=C/ P=O system. The chemical shifts and absorption coefficients determined experimentally are in agreement with the electronic structure and conformational properties calculated by ab initio methods.

Adsorption Mechanism and Structure of the Montmorillonite Complexes with (CH3)2XO (X=C, and S), (CH3O)3PO, and CH3–CN Molecules

“…Similar results were found in analogues organophosphorus compounds (36,37). The theoretical values of P=O and P-O bond lengths (0.145-0.146 and 0.157 nm, respectively) reproduce the experimental values (0.145-0.147 and 0.157 nm, respectively) of similar organooxyphosphorus compounds (36,37). The second conformer (TMP2) is 1.08 kcal/mol (at 6-31+G * //6-31+G * level) less stable than TMP1, where one methyl group is oriented in an anti disposition with respect to the phosphoryl group (θ (O=P-O-C) = 176 • ).…”

“…This is consistent with the results reported by Ewig et al (35) for the phosphoric acid molecule, where the OH groups were oriented in a similar syn-gauche disposition with respect to the phosphoryl moiety. Similar results were found in analogues organophosphorus compounds (36,37). The theoretical values of P=O and P-O bond lengths (0.145-0.146 and 0.157 nm, respectively) reproduce the experimental values (0.145-0.147 and 0.157 nm, respectively) of similar organooxyphosphorus compounds (36,37).…”

DFT and MP2 Study of the Molecular Structure and Vibrational Spectra of the Anticancer Agent Cyclophosphamide

“…Since our calculated properties of the phosphoryl PO bond in cyclophosphamide, such as bond lengths and Mulliken charges, are almost the same as in the systems Hernández-Laguna et al [22] studied, without any doubt also the phosphoryl PO bond in cyclophosphamide, in accordance with previous descriptions, can be taken as a partially polarized strong triple bond [22], leading to rather weak anomeric and conjugation effects. Thus Natural Bond Orbital calculations are not needed to justify these findings.…”

“…Although these interactions may represent a weak conjugation (also found by Hernández-Laguna et al [22] between a vinyl group and the phosphoryl PO bond), the PO bond has a high ionic character with a Mulliken charge of +1.26 on the P and of −0.56 on the O atom, and thus the effects of orbital overlaps will be much weaker than common conjugation effects. A clear indication for the presence of orbital overlaps is the almost planar structure of the PNCC group in the axial form, while this group is pyramidal in the equatorial form as already mentioned.…”

“…Note that Hernández-Laguna et al [22] published a thorough study of the phosphoryl PO bond in several compounds using localized orbitals and also Natural Fig. 2.…”