On the basis of highly accurate laboratory rest frequencies , and the first data release ( DR1 ) from a largescale , high sensitivity spectral line survey , GBT Observations of TMC-1 : Hunting for Aromatic Molecules ( GOTHAM ) , predominately in the K ( 18 - 27 GHz ) and K a bands ( 26 - 40 GHz ) , a number of the authors here recently reported the astronomical detection of 1 - cyano - CPD using spectral stacking and matched filtering techniques ( McCarthy et al . 2020b ) . From these observations , which represent ∼30 % of the project goal , an upper limit for 2 - cyano - CPD relative to 1 - cyano - CPD was estimated to be roughly 1/3 . Because the abundance ratio in the laboratory ranges from 1/2 to 1/4 ( Sakaizumi et al . 1987;McCarthy et al . 2020a ) , it was unclear if 1 - cyano - CPD is formed selectively in TMC-1 or if the apparent absence of 2 - cyano - CPD is simply a question of sensitivity , given its somewhat lower stability and consequently lower abundance . With the second data release ( DR2 ) and additional laboratory measurements , this ambiguity has now been resolved , and in doing so a common formation for this isomeric pair is implicated .