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From the same journal

Tropospheric Aqueous-Phase Free-Radical Chemistry: Radical Sources, Spectra, Reaction Kinetics and Prediction Tools

Research output: Contribution to journalArticle

Author(s)

  • Hartmut Herrmann
  • Dirk Hoffmann
  • Thomas Schaefer
  • Peter Bräuer
  • Andreas Tilgner

Department/unit(s)

Publication details

JournalChemPhysChem
DatePublished - 2010
Issue number18
Volume11
Number of pages27
Pages (from-to)3796-3822
Original languageEnglish

Abstract

The most important radicals which need to be considered for the description of chemical conversion processes in tropo- spheric aqueous systems are the hydroxyl radical (OH), the ni- trate radical (NO3 ) and sulphur-containing radicals such as the sulphate radical (SO4? ). For each of the three radicals their gen- eration and their properties are discussed first in the corre- sponding sections. The main focus herein is to summarize newly published aqueous-phase kinetic data on OH, NO3 and SO4? radical reactions relevant for the description of multi- phase tropospheric chemistry. The data compilation builds up on earlier datasets published in the literature. Since the last review in 2003 (H. Herrmann, Chem. Rev. 2003, 103, 4691– 4716) more than hundred new rate constants are available from literature. In case of larger discrepancies between novel and already published rate constants the available kinetic data for these reactions are discussed and recommendations are provided when possible. As many OH kinetic data are obtained by means of the thiocyanate (SCN? ) system in competition ki- netic measurements of OH radical reactions this system is re- viewed in a subchapter of this review. Available rate constants for the reaction sequence following the reaction of OH+SCN? are summarized. Newly published data since 2003 have been considered and averaged rate constants are calculated. Apply- ing competition kinetics measurements usually the formation of the radical anion (SCN)2? is monitored directly by absorption measurements. Within this subchapter available absorption spectra of the (SCN)2? radical anion from the last five decades are presented. Based on these spectra an averaged (SCN)2? spectrum was calculated. In the last years different estimation methods for aqueous phase kinetic data of radical reactions have been developed and published. Such methods are often essential to estimate kinetic data which are not accessible from the literature. Approaches for rate constant prediction in- clude empirical correlations as well as structure activity rela- tionships (SAR) either with or without the usage of quantum chemical descriptors. Recently published estimation methods for OH, NO3 and SO4? radical reactions in aqueous solution are finally summarized, compared and discussed.

    Research areas

  • atmospheric chemistry, kinetics, radicals, reactivity, spectroscopic methods

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