Reactions of phosphate radicals with substituted benzenes. A structure–reactivity correlation study

Reactions of Phosphate Radicals with Monosubstituted Benzenes. A Mechanistic Investigation

“…This scheme considers phosphate (HPO 3 ) elimination yielding phenoxyl radicals 4 was proposed in our previous investigations [3], in agreement with a similar pathway reported by Merga et al…”

“…Phenol. The intermediate formed by the reaction between HPO 4 .À and phenol (1; X OH) with l max at 300 and 400 nm and a second-order-decay rate constant 2k 1.7 ¥ 10 9 m À1 s À1 was assigned to the phenoxyl radical 4 (X H) [3] [22]. A similar spectrum was found for the intermediate of the reaction of H 2 PO 4 .…”

“…Chlorobenzene. The reaction of HPO 4 .À with chlorobenzene (1; X Cl) leads to formation of phenoxyl radical 4 (X Cl) [3] showing two absorption bands around 290 ± 300 nm and in the 390 ± 400 nm region, as shown in Fig. 5.…”

“…This behavior can be rationalized assuming the formation of a s adduct between the phosphate radicals and the aromatics and further elimination of phosphate ions. Therefore, the scheme proposed in [3] modifies to Scheme 1 for HPO 4 .À , where formation of the substrate radical cation 3 due to an addition/elimination route from substrate 1 via 2 is considered. Similar reactions can be written for the radicals H 2 PO 4…”

“…correlate with the electron-withdrawing ability of the substituent, as expected from the electrophilicity of these radicals [3] [4]. The proposed mechanism [5] includes both electron transfer from the aromatics to the phosphate radicals and formation of an adduct between phosphate radicals and the aromatics, which may eliminate phosphate ions leading to hydroxycyclohexadienyl radicals or phosphite ions yielding phenoxyl radicals.…”