Radiation-induced oxidation of substituted benzaldehydes: a pulse radiolysis study

Geeta, S. ; Rao, B. S. M. ; Mohan, H. ; Mittal, J. P. (2004) Radiation-induced oxidation of substituted benzaldehydes: a pulse radiolysis study Journal of Physical Organic Chemistry, 17 (3). pp. 194-198. ISSN 0894-3230

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/poc.713...

Related URL: http://dx.doi.org/10.1002/poc.713


The reactions of the oxidizing radicals hydroxyl radical (·OH), azidyl radical(N3) and sulfate radical anion(SO4-•) with hydroxy-, methoxy-, chloro- and nitro-substituted benzaldehydes were studied by pulse radiolysis. The rate constants for the ·OH reaction [k≈(2.6-12.0)× 109lmol-1s-1] with these compounds are higher than those for the or reactions [k≈(0.01-4.2)× 109lmol-1s-1]. The ·OH reaction shows a significant substituent effect which is reflected in the rate constants (k≈12.0× 109dm3mol-1s-1 with hydroxybenzaldehyde and k≈3.0× 109dm3mol-1s-1 with nitrobenzaldehyde). The transient species produced by the reaction of ·OH with the m-substituted benzaldehydes shows an absorption maximum at 370-400nm, whereas the p-substituted isomers exhibit two absorption peaks centred around 325 and 410nm, except in the case of p-nitrobenzaldehyde, which shows only a single peak at 330nm. These spectra are identical with the spectra obtained for the (N3) or SO4-• reactions with substituted benzaldehydes. ·OH adduct formation and subsequent decomposition to the corresponding phenoxyl radicals is the main reaction channel for the .OH-induced oxidation of substituted benzaldehydes. One-electron oxidation by (N3) or SO4-• of substituted benzaldehydes proceeds via an electron transfer process producing the corresponding radical cations.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
Keywords:Benzaldehydes; Radiation-induced Oxidation; Radicals; Pulse Radiolysis
ID Code:25675
Deposited On:04 Dec 2010 11:56
Last Modified:07 Jun 2011 06:04

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