Molecular richness in protostars: Lessons learnt from spectral observations

The gas associated with the early stages of star formation contains traces of a large variety of molecular species, many of which are organic in nature. Interestingly, we observe a substantial chemical diversity among protostars, with some objects being enriched in what astrochemists label interstellar complex organic molecules (iCOMs), such as methyl formate (HCOOCH3), while others are overabundant in unsaturated carbon chains such as C4H. What is the cause of this diversity? And where should we place the proto-solar-system in this chemical context: was it rich in iCOMs, or in carbon chains, or in both? Thanks to the development of sensitive broadband (sub-)millimetre instrumentation, both in single-dish telescopes and interferometers, we are currently witnessing big steps forward in this area. The present contribution summarises what we have learnt, in the past decade or so, about the molecular contents in solar-mass protostellar sources, and suggests a few guidelines to stimulate progress in the field