A large number of organic molecules have been detected in the gas phase of interstellar clouds. Interestingly, the molecules found in very cold clouds (10 K) with little star formation are exotic by terrestrial standards while the molecules found in regions of star and planet formation tend to be more terrestrial in nature. The synthesis of the exotic molecules is ironically well understood in terms of gas- phase ion-molecule reactions, which tend to produce very unsaturated species, as well as ions, both positively and negatively charged, isomers, and radicals. On the other hand, the formation of more hydrogen-rich terrestrial-type organic molecules in star-forming regions is not well understood.
Most investigators feel, however, that reactions on interstellar dust particles followed by sublimation into the gas as temperatures rise play a major role. In my talk, I will discuss current models of how complex molecules are formed in several evolutionary stages of star formation including so-called hot cores and corinos as well as protoplanetary disks.