Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637322
Title: Kinetic studies of the reactions of nitrous acid scavengers
Author: Howes, K. R.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1987
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Abstract:
A kinetic, product and isotopic study of the reaction of hydrazine with nitrous acid has been carried out. At acidities greater than 0.5M, and with excess hydrazine present, hydrazoic acid is the major product. In the presence of excess nitrous acid, nitrogen and nitrous oxide are the only products, but nitrogen-15 tracer work showed that these are not formed via the nitrous acid-hydrazoic acid reaction. It is proposed that the nitrogen and nitrous oxide are formed via the double nitrosation of hydrazine. The first species formed on the reaction of hydrazine with nitrous acid is nitroso-hydrazine. This rapidly tautomerises forming a mixture of HN= N-buildrel + over N H2-OH and buildrel + over N H3-N = N-OH. In the presence of excess nitrous acid these species are nitrosated, the products formed decomposing to nitrogen and nitrous oxide. In the absence of excess nitrous acid these species decompose slowly forming hydrazoic acid. The species buildrel + over N H3-N = N-OH absorbs in the UV, with an absorbance maximum at 223 nm. The kinetics of its formation and decomposition have been studied by stopped-flow spectrophotometry. UV studies over a longer timescale revealed the presence of a species with an absorbance maximum at 230 nm, but this is thought to be only a very minor product. The rate of the reaction of nitrous acid with excess hydrazine was measured in nitric acid solutions of up to 15M in concentrations. A maximum rate is attained in 10M nitric acid. The rate falls at higher nitric acid concentrations due to the conversion of nitrous acid to dinitrogen tetroxide. A kinetic study was carried out on the reaction of hydrazoic acid with nitrous acid. The formation reaction of dinitrogen trioxide has an activation energy of 56 kJ mo1-1. The azide ion reacts with dinitrogen triozide at close to the encounter controlled rate. At high initial pH values, the pH rises as the reaction of nitrous acid with hydrazoic acid proceeds. A Gear numerical integration computer model can succesfully predict the variation of pH with time for this partially acidified system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.637322  DOI: Not available
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