Gas Phase Chemistry Leading to Interstellar Complex Organic Molecules: There is Still Much to Learn

Around 270 molecules have been identified in interstellar and circumstellar medium by astronomical observations, among which ca. 90 contain at least six atoms and can be considered relatively complex. These molecules are referred to as interstellar complex organic molecules (iCOMs). In many cases, their formation routes have not been established yet and a possible role of interstellar dust grains and their icy mantles has been invoked. More than 8000 gas-phase reactions are included in the databases for astrochemical modelling, but only a small percentage of them has been characterized in laboratory experiments or via theoretical calculations. A lot of work remains to be done before we can claim we have understood interstellar gas-phase chemistry and its complexity. The spatial distributions of iCOMs via interferometric detection campaigns and the improved sensitivity of radiotelescopes will provide stringent tests for astrochemical modelling and proposed formation routes of iCOMs.