The redox potential of the azide/azidyl couple

Zeev B. Alfassi, Anthony Harriman, Robert E. Huie, S. Messeri, P. Neta

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103 Scopus citations


Pulse radiolysis experiments were carried out with neutral aqueous solutions containing azide with iodide, bromide, or thiocyanate to examine possible one-electron transfer rates and equilibria involving the N3̇/N3- couple. The N3 radical was found to oxidize I- with a rate constant of 4.5 × 108 M-1 s-1. No reaction was observed between I2̇- and N3-. With Br-, however, the system reached equilibrium, Br2̇- + N3- ⇌ 2Br- + N3̇, with kf = 4.0 × 108 M-1 s-1 and kr = 7.3 × 103 M-2 s-1. From the equilibrium constant K = 5.5 × 104 M and the redox potential E(Br2̇-/2Br-) = 1.63 V we calculate E(N3̇/N3-) = 1.35 ± 0.02 V vs. NHE. Cyclic voltammetry experiments with N3- showed a single peak on the anodic scan and no peak on the cathodic scan due to the rapid decay of the N3 radicals. From the dependence of peak potential on scan rate we derive E1/2 for the N3̇/N3- couple, 1.32 ± 0.03 V vs. NHE.

Original languageEnglish
Pages (from-to)2120-2122
Number of pages3
JournalJournal of Physical Chemistry
Issue number8
StatePublished - 1 Jan 1987

ASJC Scopus subject areas

  • General Engineering
  • Physical and Theoretical Chemistry


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