Electron inductive effects in the radiolysis of substituted phenylboronic acid solutions

Abstract

The pulse radiolysis of aqueous solutions of phenylboronic acid PhB(OH)₂ and its m-nitro and m-amino derivatives has been investigated. The transient optical absorption spectra indicate the presence of three intermediate species absorbing with independent niaxima at 297, 317 and 400 nm. The 297-nm band has been assigned to the anion formed in an electron capture reaction, i.e. PhB(OH)₂+e_aq- → PhB(OH)₂- and the 317-nm band to cyclohexadienyl radicals formed from OH and H attack on PhB(OH)₂. Hydroxyphenylboronic acid has been identified as the major stable radiation product. For each of the systems studied the respective yield and reactivity of observed intermediate species can be interpreted relative to the electron inductive effects of substituent groups in agreement with the Hammett relationship.