Reaction rates of the CN radical with diacetylene and dicyanoacetylene

Rates of CN reactions with diacetylene (DA) and dicyanoacetylene (DCA) have been measured at room temperature from the decay of the CN radical at various sample pressures by laser induced fluorescence. The rate constants are (4.2 +/- 0.2) x 10(-10) and (5.4 +/- 0.2) x 10(-13) in units of cm(3) molec(-1) s(-1) for DA and DCA, respectively, which follow the general pattern of CN reactions with hydrocarbons and nitriles. In the lower temperature circumstellar envelopes and Titan's atmosphere, the CN reaction with C4H2 may be more important, while the reaction with C4N2 may become less important.