  We present high sensitivity observations of the complex organic molecules
(COMs) CH3OH, C2H5OH, HCOOCH3, HCOOH and H2CO and of SiO toward the quiescent
dark cloud L183 and the molecular outflow L1448-mm. We have not detected
C2H5OH, HCOOCH3 and SiO in L183 and in the quiescent gas of L1448-mm. The
abundances of CH3OH, H2CO and SiO are enhanced by factors 4-20 in the shock
precursor component, and those of CH3OH and SiO by 3 and 4 orders of magnitude
in the shocked gas, without substantial changes (< factor of 2) in the
abundances of C2H5OH and HCOOCH3 relative to that of CH3OH. The large
enhancements of SiO and CH3OH can be explained by the shock ejection of an
important fraction of the grain mantle material into gas phase. Our upper
limits to the C2H5OH/CH3OH and HCOOCH3/CH3OH ratios are consistent with the
rather constant ratios measured in hot cores and Galactic center clouds.
However, the upper limits to the HCOOCH3/CH3OH and the HCOOH/CH3OH ratios are
at least one order of magnitude smaller than those found in"hot corinos"
surrounding low mass protostars. We speculate that the observed abundances of
COMs in different objects are consistent with a sort of "universal" grain
mantle composition which is locally changed by the processes of low mass star
formation.
