Reaction of Hydroxyl Radical with Aromatic Hydrocarbons in Nonaqueous Solutions:  A Laser Flash Photolysis Study in Acetonitrile

Abstract

Laser flash photolysis (LFP) of acetonitrile solutions of N-hydroxypyridin-2-thione in the presence of trans-stilbene generates a transient absorbance at 392 nm, attributed to the addition of hydroxyl radical to stilbene. The observed transient absorbance was used in competitive LFP experiments to determine relative rates of reaction for hydroxyl radical with a range of aromatic hydrocarbons in acetonitrile. Structure-reactivity relationships for the reaction of hydroxyl radical with arenes are derived. With these aromatic hydrocarbons, we observe a good correlation between the rates of hydroxyl-radical reaction and the ionization potential of the arene. Kinetic isotope effects are consistent with hydroxyl-radical addition being the dominant reaction pathway with the arene.

Hydroxyl radical reactions with halogenated ethanols in aqueous solution: Kinetics and thermochemistry

“…Correlations between reaction rates and extra kinetic parameter, such as bond dissociation energies (BDEs) or ionization potentials (IPs), have been used successfully in the literature to better understand the mechanism of a chemical reaction and to estimate unknown reaction parameters, both in the gas phase [17] and in the solution phase [20][21][22][23][24][25][26]. In the present study, correlations of the observed rate constants and activation energies with calculated BDEs as well as IPs are presented for the reactions of OH radicals with HEs, and finally the atmospheric implications of the study are discussed.…”

Hydroxyl radical electrochemically generated with water as the complete atom source and its environmental application

“…transition metal complex) or poisonous solvents (e.g. acetonitrile), which frequently cause problems in separation and even bring about secondary environmental contamination [12,13] . It is desirable to develop a cleaner approach to produce the most ideal oxidants.…”

Kinetic studies of the reaction between pesticides and hydroxyl radical generated by laser flash photolysis

“…Systematic photophysical studies such as LFP can be employed to establish the role of the hydroxyl radical in the degradation of pesticides under various oxidative conditions . Although hydroxyl radicals do not absorb in the visible region (300–700 nm) and cannot be directly detected by conventional LFP, they can be detected indirectly via their reaction with a compound that generates a spectroscopically detectable intermediate . A suitable system for the production of hydroxyl radicals by LFP is the photolysis MNO using a 355 nm Nd‐YAG laser pulse, which also produces the pyrithiyl radical absorbing at 490 nm [Eqn ]: …”

“…Competitive kinetic experiments between the pesticide of interest and TS, which cause a pesticide‐concentration‐dependent reduction in the signal at 390 nm due to the hydroxyl radical–TS adduct can then be used to determine the rate constant for reaction between the hydroxyl radical and the pesticide of interest …”

“…LFP is a technique used to study transient species generated by an intense, several nanosecond‐long light pulse from a pulsed laser source, monitoring the decay and spectra of these species by absorption spectroscopy. A particularly convenient LFP method for studying the reactivity of HO • is to generate HO • by direct photolysis of 2‐mercaptopyridine‐ N ‐oxide in acetonitrile and use trans ‐stilbene to capture HO • , which results in the formation of an adduct with a characteristic absorption peak at 390 nm . Advantages of this method are that it avoids the use of hydrogen peroxide as a radical promoter, does not generate other interfering radicals and allows indirect monitoring of the generation of HO • by the concomitant formation of the readily detectable pyridinethiyl radical at 490 nm .…”