A study of the radiation chemistry of phosphorous compounds

Abstract

The partial charges of atoms of a number of organophosphorous compounds were calculated by the method of iterative partial equalization of orbital electron negativity (PEOE) presented by Gasteiger and Marsili, and from the calculated partial charges of carbon atoms of the ester alkyl groups in three stereoisomers each for tributylphosphate and dibutylphenylphosphonate, it was found that in all cases the carbon at the α-position to oxygen possesses the largest density of positive charge, such that the C α—C β bonds were more readily broken than other C—C bonds. The experimental results supported this conclusion by examining the G-values of gaseous alkane (alkene) radiation products. From the low temperature measured esr spectra of several phosphates and phosphonates γ-irradiated at 77°K and it was seen that these spectra were composed of several radicals formed by different reaction processes. Like TMP, the esr spectrum of dimethyl methylphosphate irradiated in low temperature contained also four kinds of radicals. The net atomic charges as well as the values of mulliken population matrix condensed to atoms were calculated by CNDO/2 MO and by ab initio MO methods for comparison. In all cases the net atomic charges of the carbon in C—P bonds were positive. Since the phosphoryl radical was found in esr spectrum of DMMP, it implied that the C—P bonds were also broken during irradiation. In our work, the products of C—P fission were truly found and their G-values were determined by gas chromatography. For studying of energy transfer, two binary systems (TBP-DPPP and TBP-benzene) were irradiated and the G-values of polymer, di-and monobasic acids were measured and compared. In these systems the intermolecular energy transfer were predominate. DPPP had higher scavenging effect than benzene.