Collect. Czech. Chem. Commun. 1981, 46, 1560-1565

Photoinduced decomposition of aryldiazonium salts

Jaromír Jirkovskýa, Anton Fojtíka and Heinz Georg Osmar Beckerb

a The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 110 00 Prague 1
b Technische Hochschule „Carl Schorlemmer", 42 Merseburg, GDR


Flash photolysis of 1,4-benzoquinone (10-3 mol l-1) in an acetonitrile/water mixture (16 : 9 v/v) leads in the presence of 2,4,6-tri-tert-butylphenol (5 . 10-2 mol l-1) to semiquinone- and phenoxy radicals. In this paper the reactivity of semiquinone with benzenediazonium tetrafluoroborate and six of its para substituted derivatives was studied. A significant effect of the substituents on the reaction rate was observed and the direct electron transfer from semiquinone to the diazonium salt was found to be the rate determining step. Different reactivity of the acid-base forms of semiquinone leads, depending on the pH, to rate constant changes within a range of five orders of magnitude.