The redox potential of the azide/azidyl couple

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

doi:10.1021/j100292a029

The redox potential of the azide/azidyl couple

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

Unit of Nuclear Engineering

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Abstract

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 N₃^̇/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 I₂^̇- and N₃^-. With Br^-, however, the system reached equilibrium, Br₂^̇- + N₃^- ⇌ 2Br^- + N₃^̇, with k_f = 4.0 × 10⁸ M^-1 s^-1 and k_r = 7.3 × 10³ M^-2 s^-1. From the equilibrium constant K = 5.5 × 10⁴ M and the redox potential E(Br₂^̇-/2Br^-) = 1.63 V we calculate E(N₃^̇/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 E_1/2 for the N₃^̇/N₃^- couple, 1.32 ± 0.03 V vs. NHE.

Original language	English
Pages (from-to)	2120-2122
Number of pages	3
Journal	Journal of Physical Chemistry
Volume	91
Issue number	8
DOIs	https://doi.org/10.1021/j100292a029
State	Published - 1 Jan 1987

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General Engineering
Physical and Theoretical Chemistry

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@article{16656c103c9649f0b3773017fe7b2ab8,

title = "The redox potential of the azide/azidyl couple",

abstract = "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 N{\.3}/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 I{\.2}- and N3-. With Br-, however, the system reached equilibrium, Br{\.2}- + N3- ⇌ 2Br- + N{\.3}, 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(Br{\.2}-/2Br-) = 1.63 V we calculate E(N{\.3}/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 N{\.3}/N3- couple, 1.32 ± 0.03 V vs. NHE.",

author = "Alfassi, {Zeev B.} and Anthony Harriman and Huie, {Robert E.} and S. Messeri and P. Neta",

year = "1987",

month = jan,

day = "1",

doi = "10.1021/j100292a029",

language = "English",

volume = "91",

pages = "2120--2122",

journal = "Journal of Physical Chemistry",

issn = "0022-3654",

publisher = "American Chemical Society",

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TY - JOUR

T1 - The redox potential of the azide/azidyl couple

AU - Alfassi, Zeev B.

AU - Harriman, Anthony

AU - Huie, Robert E.

AU - Messeri, S.

AU - Neta, P.

PY - 1987/1/1

Y1 - 1987/1/1

N2 - 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.

AB - 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.

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U2 - 10.1021/j100292a029

DO - 10.1021/j100292a029

M3 - Article

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SN - 0022-3654

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SP - 2120

EP - 2122

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

IS - 8

ER -

The redox potential of the azide/azidyl couple

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