In situ photolysis-electron spin resonance study of some reactions of phosphate radicals

Journal Article · Thu Oct 06 04:00:00 UTC 1977 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100535a012· OSTI ID:7282850

Maruthamuthu, P; Taniguchi, H

Free radical intermediates formed in the reaction of phosphate radicals (PO/sub 4//sup 2 -/ or its protonated forms, HPO/sub 4//sup -/ and H/sub 2/PO/sub 4/) with a number of fundamental organic and inorganic compounds have been studied by the in situ photolysis-steady state ESR method. The phosphate radicals were generated effectively by the photolysis of peroxodiphosphate (P/sub 2/O/sub 8//sup 4 -/) in aqueous solutions. Though the phosphate radical itself could not be detected directly, the ESR spectra of the phosphate radical adducts to fumaric and maleic acids and also the aci-anion of nitromethane were observed successfully. The pK/sub a/ value for the proton dissociation in the phosphate group of the adduct to fumaric and maleic acids, /sup -/OOCCH(OPO/sub 3/H/sup -/)CHCOO/sup -/, has been determined to be 6.7. The reactions of phosphate radicals are rather similar to those of the related active species SO/sub 4//sup -/, e.g., they give rise to hydroxyalkyl radicals from aliphatic alcohols, adduct radicals with unsaturated compounds, and inorganic radicals such as CO/sub 3/ from HCO/sub 3/ and PO/sub 3//sup 2 -/ from HPO/sub 3//sup 2 -/. However, there are notable differences in reactions with aliphatic and aromatic carboxylic acids. From saturated aliphatic mono- and dicarboxylic acids, ..cap alpha..-carbon radicals produced by hydrogen abstraction with phosphate radicals were predominantly detected in neutral aqueous solutions and phenyl-type radicals were not detected from aromatic carboxylic acids. On the contrary the resultant radicals by decarboxylation were mainly observed in SO/sub 4//sup -/ system. Clearly, direct oxidative electron transfer is not the predominant process in the reaction of the phosphate radical (HPO/sub 4//sup -/) with carboxylic acids.

• Research Organization: Univ. of Notre Dame, IN
• OSTI ID: 7282850
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 81:20; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ACID PHOSPHATES
ANIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
DECOMPOSITION
ELECTRON SPIN RESONANCE
IONS
MAGNETIC RESONANCE
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADICALS
RESONANCE