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RATE CONSTANTS FOR INTERACTION OF 1 O 2 1 Δ g ) WITH AZIDE ION IN WATER
Author(s) -
Haag Werner R.,
Mill Theodore
Publication year - 1987
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1987.tb05381.x
Subject(s) - hydrazoic acid , azide , chemistry , protonation , quenching (fluorescence) , reaction rate constant , ion , photochemistry , inorganic chemistry , kinetics , fluorescence , organic chemistry , physics , quantum mechanics
— The rate constant for quenching of 1 O 2 by azide ion in water was determined to be (5.0 ± 0.4) × 10 8 M −1 s −1 using a variety of sensitizers (including humic acids) and 1 O 2 acceptors. The apparent second‐order rate constant decreases with pH below pH 5.5 in accordance with the protonation of azide ion to form hydrazoic acid (p K a = 4.6). Quenching by hydrazoic acid is at least 2 orders of magnitude slower than by azide ion. Greater than 99% of all interactions between 1 O 2 and azide ion involve physical quenching rather than chemical reaction. Humic acid triplets are not significantly quenched by azide ion at concentrations less than 2 m M , allowing azide ion quenching to be used as a diagnostic test for the intermediacy of 1 O 2 in photosensitized oxidations in natural surface waters.