Characterization and implementation of pulsed -accelerated -flow spectrometer model V, and, Nucleophilic assistance in the nitrogen dioxide reaction with chlorine dioxide

Robert H Becker, Purdue University

Abstract

A pulsed-accelerated-flow (PAF) spectrometer (model V) capable of non-ambient temperature studies of fast reaction kinetics is constructed and used for collection of kinetic data. The instrument is used to study the kinetics of the following reactions at various temperatures: the W(CN)8 4−/IrCl62− reaction, the reverse bromine hydrolysis (HOBr + Br− + H+ → Br2 + H2O) reaction, the BrCl hydrolysis reaction, the bromine/tribromide/hydrogen sulfite reactions, and the IBr hydrolysis reaction. A study of the ClO2/NO2 reaction using stopped-flow spectroscopy is also conducted. The loss of chlorine dioxide (ClO2) is followed when reacted with excess NO2− in the presence of a large concentration of ClO2− . The concentrations of these species are set to establish a pre-equilibrium where nitrogen dioxide (NO2) is also present. These conditions enable the study of the ClO2 reaction with nitrogen dioxide (NO 2) and the NO2 disproportionation. The rate of the NO2/ClO2 electron-transfer reaction is accelerated by different nucleophiles (NO2− > Br > OH − > CO32− > PO4 3− > ClO2− > H2O). The rate constants for the nucleophile-assisted reactions (kNu, M−2s−1) at 25°C vary from 4.4 × 106 for NO2 to 2.0 × 103 when H2O is the nucleophile. The concurrent NO2 disproportionation exhibits no nucleophilic effect and has a rate constant of 4.8 × 10 7 M−1 s−1. Ion chromatography is used to elucidate the products of the O3/BrO2 − reaction and the HOBr/NO2 reaction. The products of the O3BrO2− reaction are O 2 and BrO3− in a 1:1 BrO2 −/BrO3− ratio, while the products of the HOBr/NO2− reaction are the 1:1 formation of Br− and NO3−. Finally, work on the bromite/nitrite reaction is presented.

Degree

Ph.D.

Advisors

Margerum, Purdue University.

Subject Area

Analytical chemistry|Chemistry

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