  Hot molecular cores (HMCs), the cradles of massive stars, are the most
chemically rich sources in the Galaxy. The typical masses of these cores (few
hundreds of solar masses) make them the most important reservoirs of complex
organic molecules (COMs), including key species for prebiotic processes. This
rich chemistry is thought to be the result of the evaporation of dust grain
mantles by the strong radiation of the deeply embedded early-type star(s). Our
own Sun may have been born in a high-mass star-forming region, so our Earth may
have inherited the primordial chemical composition of its parental hot core
region, as suggested by recent studies of oxygen and sulfur chemistry in
comets. In this chapter, we discuss how the next generation Very Large Array
(ngVLA) can help us to study the emission of heavy COMs in both low- and
high-mass star-forming regions. The emission of COMs is important not only
because it allows us to understand how chemistry may have developed to
eventually form life in our Earth, but also because COMs are a powerful tool
for studying the physical properties and kinematics of the dense regions very
close to the central protostars.
