Rate constants for the reactions of CN with C_6-C_8 unsaturated hydrocarbons: the relations between the reaction rates and the molecular lengths

摘要

Rates of CN reactions with 1, 3, 5-hexatriene and three octadiynes have been measured at various sample pressure using laser-induced fluorescence of the CN radical. The rate constants are, in units of cm~3 molecule~(-1) s~(-1), k_(1, 3, 5-hexatriene) = (6.7 +- 0.2) * 10~(-10), k_(1, 7-octadiyne) = (3.5 +- 0.3) * 10~(-10), k_(2, 6-octadiyne) = (2.4 +- 0.3) * 10~(-10) and k_(3, 5-octadiyne) = (2.5 +- 0.3) * 10~(-10), respectively. It shows clearly that two factors which influence the reaction rates of CN with unsaturated hydrocarbons are important. One is the length of #pi#-conjugated system, the other is the difference between elimination processes after CN insertion.