AB-INITIO CALCULATIONS ON P-C BOND-CLEAVAGE IN PHOSPHORANYL RADICALS - IMPLICATIONS FOR THE BIODEGRADATION OF ORGANOPHOSPHONATE DERIVATIVES

Barrier heights for P-C bond homolysis in P-hydroxy-P-methyl-P,P-dioxo phosphoranyl and P,P,P-trihydroxy-P-methylphosphoranyl were calculated using well correlated levels of electronic structure theory. The best estimate for the difference in barriers between the two indicates tha t homolysis is more facile for P,P,P-trihydroxy-P-methylphosphoranyl b y roughly 9 kcal mol(-1). This result suggests that bacterial pathways leading to P-C bond cleavage in organophosphonate derivatives will pr eferentially proceed via initial one-electron reduction of substrates rather than oxidation. (C) 1998 John Wiley & Sons, Ltd.