UNSPECIFIED (1991) INTERACTION OF HALIDE AND PSEUDOHALIDE IONS WITH THE TRIPLET-STATE OF 1-NITRONAPHTHALENE - EFFECT OF ACIDITY - A FLASH-PHOTOLYSIS STUDY. JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 87 (22). pp. 3617-3624. ISSN 0956-5000

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Abstract

The interaction of halide, pseudohalide and hydroxide ions (X-) with the lowest excited triplet state of 1-nitronaphthalene (3NN) has been investigated by laser and conventional flash photolysis. One-electron transfer was demonstrated for CN-, SCN- and OH- ions, and the results for quenching effect of the inorganic anions examined have been interpreted in terms of one-electron transfer from X- to 3NN. The effect of acidity on the triplet lifetime and on the reactivity of 3NN towards these anions was studied. In particular, it was found that Cl- ion constant, quenches the triplet state of NN with a second-order rate constant, k2, which at H(o) almost-equal-to -2.0 is higher by a factor of 5 x 10(3) than that measured at neutral pH. The dependence of k2 on the acidity of the medium enabled the pK(a) of the protonated 3NN to be determined as -0.66 +/- 0.02 in 25% (v/v) ethanol-water. A satisfactory correlation of log k2 with the free-energy change, estimated form the electrode potentials of the couples involved, was obtained using the Rehm-Weller empirical free-energy relationship. A ground-state concentration dependence of the lifetime of 3NN was found in acetonitrile, and in aqueous acetonitrile, and the self-quenching suggested to involve one-electron transfer. In 50% (v/v) aqueous ethanol the 1-hydroxyethyl radical, generated in the H-atom abstraction reaction of 3NN with ethanol, was shown to reduce NN by both an outer-sphere and an addition/elimination mechanism.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QC Physics
Journal or Publication Title:	JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
Publisher:	ROYAL SOC CHEMISTRY
ISSN:	0956-5000
Date:	21 November 1991
Volume:	87
Number:	22
Number of Pages:	8
Page Range:	pp. 3617-3624
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/22353

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