Abstract
The rates of CN reactions with C 2 H 2 , C 2 H 4 and C 4 H 4 (vinylacetylene) have been measured by the method of laser photolysis/ laser-induced fluorescence. These rates were well fit by the following three-parameter Arrhenius expressions (in units of cm 3 /s); k C 2 H 2 = 5.67 × 10 -9 T -0.55 exp (-4.0/T), k C 2 H 4 = 1.72 × 10 -10 T -0.035 exp(160/T), k C 4 H 4 = 1.07 × 10 -7 T -0.82 exp (-228/T). Though the olefinic and acetylinic CH bond strenghts differ significantly in C 2 H 2 and C 2 H 4 the reaction rates in C 2 H 2 and C 2 H 4 are very similar. This indicates that the reactions most likely occur by addition to unsaturated carboncarbon bonds. The rate for CN+C 4 H 4 is approximately the sum of k C 2 H 2 and k C 2 H 4 , indicating that the double and triple bond in C 4 H 4 are equally reactive as in C 2 H 2 . Conventional TST-RRKM results were unable to account for the slight negative temperature dependence of the CN+C 2 H 2 and CN+C 2 H 4 reaction rates. However, the approximate method introduced by Forst for calculating the specific rate constants for the decomposition of the CNC 2 H 2 and CNC 2 H 4 adducts yielded correct temperature dependences.
| Original language | English |
|---|---|
| Pages (from-to) | 317-325 |
| Number of pages | 9 |
| Journal | Chemical Physics |
| Volume | 160 |
| Issue number | 2 |
| DOIs | |
| State | Published - 1 Mar 1992 |