Interstellar chemistry - Polycyanoacetylene formation

It is argued that interstellar polycyanoacetylenes are formed not on dust grains by catalytic buildup or by dissociation of longer molecules, but rather by gas phase ion-molecule reactions. The primary evidence for this view is the detection of deuterated cyanoacetylene in an interstellar cloud. It is also argued that the relative abundance of successive homologs of polycyanoacetylenes rules out the grain catalysis theory.