  Molecules with an amide functional group resemble peptide bonds, the
molecular bridges that connect amino acids, and may thus be relevant in
processes that lead to the formation of life. In this study, the solid state
formation of some of the smallest amides is investigated in the laboratory. To
this end, CH$_{4}$:HNCO ice mixtures at 20 K are irradiated with far-UV
photons, where the radiation is used as a tool to produce the radicals required
for the formation of the amides. Products are identified and investigated with
infrared spectroscopy and temperature programmed desorption mass spectrometry.
  The laboratory data show that NH$_{2}$CHO, CH$_{3}$NCO, NH$_{2}$C(O)NH$_{2}$,
CH$_{3}$C(O)NH$_{2}$ and CH$_{3}$NH$_{2}$ can simultaneously be formed. The
NH$_{2}$CO radical is found to be key in the formation of larger amides. In
parallel, ALMA observations towards the low-mass protostar IRAS 16293-2422B are
analysed in search of CH$_{3}$NHCHO (N-methylformamide) and
CH$_{3}$C(O)NH$_{2}$ (acetamide). CH$_{3}$C(O)NH$_{2}$ is tentatively detected
towards IRAS 16293-2422B at an abundance comparable with those found towards
high-mass sources. The combined laboratory and observational data indicates
that NH$_{2}$CHO and CH$_{3}$C(O)NH$_{2}$ are chemically linked and form in the
ice mantles of interstellar dust grains. A solid-state reaction network for the
formation of these amides is proposed.
