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@INPROCEEDINGS{Vereecken:889018,
      author       = {Vereecken, Luc and Vu, G. H. T. and Nguyen, H. M. T.},
      title        = {{S}tructure-activity relationships for unimolecular
                      reactions of peroxy radicals, {RO}2, at atmospheric
                      temperatures},
      reportid     = {FZJ-2020-05392},
      year         = {2020},
      abstract     = {The oxidation of most organic matter emitted to the
                      atmosphere proceeds by radical reaction steps, where peroxy
                      radicals, ROO•, are critical intermediates formed by
                      addition of O2 molecules to carbon-based radicals. The
                      chemistry of these RO2 radicals in high-NOx conditions is
                      well-known, forming alkoxy radicals and NO2. In low-NOx and
                      pristine conditions, the RO2 radicals react with HO2 and
                      other R'O2 radicals, but can have a sufficiently long
                      lifetime to also undergo unimolecular reactions. Hydrogen
                      atom migration, forming a hydroperoxide (-OOH) and a new
                      peroxy radical site after addition of an additional O2 on
                      the newly formed radical site, has been studied extensively
                      in some compounds, such as isoprene where it was shown to be
                      the a critical step in OH radical regeneration. RO2 ring
                      closure reactions have likewise been studied, where for
                      β-pinene it has been shown to be a critical step governing
                      the yield of the decomposition products such as acetone and
                      nopinone.Despite the interest in RO2 unimolecular reactions,
                      and the potential impact on atmospheric chemistry, no widely
                      applicable structure-activity relationships (SARs) have been
                      proposed to allow systematic incorporation of such
                      unimolecular reactions in gas phase atmospheric kinetic
                      models. In this work, we present a series of systematic
                      theoretical predictions on the site-specific rate
                      coefficients for such reactions for a wide range of
                      molecular substitutions. Combined with extensive literature
                      data this allows for the formulation of a SAR for RO2
                      unimolecular reactions, covering aliphatic, branched, and
                      unsaturated RO2 with oxo, hydroxy, hydroperoxy, nitrate,
                      carboxylic acid, and ether substitutions.The predictions are
                      compared to experimental and theoretical data, including
                      multi-functionalized species. Though some molecular classes
                      are well represented in the training set (e.g. aliphatic
                      RO2), other classes have little data available and
                      additional work is needed to enhance and validate the
                      reliability of the SAR. Direct experimental data is scarce
                      for all RO2 classes. The fastest H-migrations are found to
                      be for unsaturated RO2, with the double bond outside the
                      H-migration TS ring. Ring closure of unsaturated RO2 are
                      likewise fast if the product radical carbon is exocyclic to
                      the newly formed peroxide ring.},
      month         = {May},
      date          = {2020-05-04},
      organization  = {EGU General Assembly, virtual
                       (Austria), 4 May 2020 - 8 May 2020},
      subtyp        = {Invited},
      cin          = {IEK-8},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243)},
      pid          = {G:(DE-HGF)POF3-243},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/889018},
}