  Gas-phase complex organic molecules are commonly detected toward high-mass
protostellar hot cores. Detections toward low-mass protostars and outflows are
comparatively rare, and a larger sample is key to investigate how the chemistry
responds to its environment. Guided by the prediction that complex organic
molecules form in CH3OH-rich ices and thermally or non-thermally evaporate with
CH3OH, we have identified three sight-lines in the Serpens core - SMM1, SMM4
and SMM4-W - which are likely to be rich in complex organics. Using the IRAM
30m telescope, narrow lines (FWHM of 1-2 km s-1) of CH3CHO and CH3OCH3 are
detected toward all sources, HCOOCH3 toward SMM1 and SMM4-W, and C2H5OH not at
all. Beam-averaged abundances of individual complex organics range between 0.6
and 10% with respect to CH3OH when the CH3OH rotational temperature is applied.
The summed complex organic abundances also vary by an order of magnitude, with
the richest chemistry toward the most luminous protostar SMM1. The range of
abundances compare well with other beam-averaged observations of low-mass
sources. Complex organic abundances are of the same order of magnitude toward
low-mass protostars and high-mass hot cores, but HCOOCH3 is relatively more
important toward low-mass protostars. This is consistent with a sequential ice
photochemistry, dominated by CHO-containing products at low temperatures and
early times.
