Formation of Complex Molecules in Prestellar Cores: a Multilayer
  Approach
  We present the results of chemical modeling of complex organic molecules
(COMs) under conditions typical for prestellar cores. We utilize an advanced
gas-grain astrochemical model with updated gas-phase chemistry, with a
multilayer approach to ice-surface chemistry and an up-to-date treatment of
reactive desorption based on recent experiments of Minissale et al. (2016).
With the chemical model, radial profiles of molecules including COMs are
calculated for the case of the prototypical prestellar core L1544 at the
timescales when the modeled depletion factor of CO becomes equal to that
observed. We find that COMs can be formed efficiently in L1544 up to the
fractional abundances of 10(-10) wrt. total hydrogen nuclei. Abundances of many
COMs such as CH3OCH3, HCOOCH3, and others peak at similar radial distances of
~2000-4000 AU. Gas-phase abundances of COMs depend on the efficiency of
reactive desorption, which in turn depends on the composition of the outer
monolayers of icy mantles. In prestellar cores, the outer monolayers of mantles
likely include large fractions of CO and its hydrogenation products, which may
increase the efficiency of reactive desorption according to Minissale et al.
(2016), and makes the formation of COMs efficient under conditions typical for
prestellar cores, although this assumption is yet to be confirmed
experimentally. The hydroxyl radical (OH) appears to play an important role in
gas-phase chemistry of COMs, which makes it deserving further detailed studies.
