TY - JOUR
T1 - Nitrogen Dioxide Reaction with Nitroxide Radical Derived from Hydroxamic Acids
T2 - The Intermediacy of Acyl Nitroso and Nitroxyl (HNO)
AU - Maimon, Eric
AU - Samuni, Amram
AU - Goldstein, Sara
N1 - Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/4/19
Y1 - 2018/4/19
N2 - Hydroxamic acids (RC(O)NHOH) form a class of compounds that display interesting chemical and biological properties The chemistry of RC(O)NHOH) is associated with one- and two-electron oxidations forming the respective nitroxide radical (RC(O)NHO•) and acyl nitroso (RC(O)N O), respectively, which are relatively unstable species. In the present study, the kinetics and mechanism of the •NO2 reaction with nitroxide radicals derived from acetohydroxamic acid, suberohydroxamic acid, benzohydroxamic acid, and suberoylanilide hydroxamic acid have been studied in alkaline solutions. Ionizing radiation was used to generate about equal yields of these radicals, demonstrating that the oxidation of the transient nitroxide radical by •NO2 produces HNO and nitrite at about equal yields. The rate constant of •NO2 reaction with the nitroxide radical derived from acetohydroxamic acid has been determined to be (2.5 ± 0.5) × 109 M-1 s-1. This reaction forms a transient intermediate absorbing at 314 nm, which decays via a first-order reaction whose rate increases upon increasing the pH or the hydroxamic acid concentration. Transient intermediates absorbing around 314 nm are also formed during the oxidation of hydroxamic acids by H2O2 catalyzed by horseradish peroxidase. It is shown that HNO is formed during the decomposition of these intermediates, and therefore, they are assigned to acyl nitroso compounds. This study provides for the first time a direct spectrophotometric detection of acyl nitroso compounds in aqueous solutions allowing the study of their chemistry and reaction kinetics.
AB - Hydroxamic acids (RC(O)NHOH) form a class of compounds that display interesting chemical and biological properties The chemistry of RC(O)NHOH) is associated with one- and two-electron oxidations forming the respective nitroxide radical (RC(O)NHO•) and acyl nitroso (RC(O)N O), respectively, which are relatively unstable species. In the present study, the kinetics and mechanism of the •NO2 reaction with nitroxide radicals derived from acetohydroxamic acid, suberohydroxamic acid, benzohydroxamic acid, and suberoylanilide hydroxamic acid have been studied in alkaline solutions. Ionizing radiation was used to generate about equal yields of these radicals, demonstrating that the oxidation of the transient nitroxide radical by •NO2 produces HNO and nitrite at about equal yields. The rate constant of •NO2 reaction with the nitroxide radical derived from acetohydroxamic acid has been determined to be (2.5 ± 0.5) × 109 M-1 s-1. This reaction forms a transient intermediate absorbing at 314 nm, which decays via a first-order reaction whose rate increases upon increasing the pH or the hydroxamic acid concentration. Transient intermediates absorbing around 314 nm are also formed during the oxidation of hydroxamic acids by H2O2 catalyzed by horseradish peroxidase. It is shown that HNO is formed during the decomposition of these intermediates, and therefore, they are assigned to acyl nitroso compounds. This study provides for the first time a direct spectrophotometric detection of acyl nitroso compounds in aqueous solutions allowing the study of their chemistry and reaction kinetics.
UR - http://www.scopus.com/inward/record.url?scp=85045657870&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.8b02300
DO - 10.1021/acs.jpca.8b02300
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C2 - 29608853
AN - SCOPUS:85045657870
SN - 1089-5639
VL - 122
SP - 3747
EP - 3753
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 15
ER -