Title:  Cycloaddition reactions of CF with unsaturated hydrocarbons. Correlation of activation energies and frequency factors with the hydrocarbon ionization energies 
Authors:  DeBoelpaep, I Vetters, B Peeters, Jozef # × 
Issue Date:  Jan1997 
Publisher:  Amer chemical soc 
Series Title:  Journal of Physical Chemistry A vol:101 issue:5 pages:787793 
Abstract:  Absolute rate coefficients of the elementary reactions of CF(X(2) Pi,v=0) with a series of unsaturated hydrocarbons have been measured for the first time over an extended temperature range. The rate coefficients of the CF reactions with ethene, propene, isobutene and 2,3dimethyl2butene, as well as with allene, 1,3butadiene, isoprene, and propyne, have been determined at temperatures between 294 and 455 K and at pressures in the 210 Torr range, using pulse laser photolysislaserinduced fluorescence (PLPLIF) techniques. The rate constants of the reactions of CF with lbutene, cis2butene, and trans2butene have been determined at 294 K. The CF(X(2) Pi) radicals were generated by excimer laser multiphoton dissociation of CF2Br2 at 248 nm. Pseudofirstorder exponential decays of CF(X,v=0) were monitored by LIF (excitation at the P11 band head of the A(2) Sigma(+), v' = 1 < X(2) Pi, v '' = 0 transition) at varying concentrations of the coreactant, always in very large excess over CF. Pressure effects were not observed. The rate coefficients, in units of cm(3) molecule(1) s(1), can be expressed by the following Arrhenius equations: k(CF+C2H4) = (8 +/ 1) x 10(13) exp{(700 +/ 96)/T}, k(CF+C3H6)= (9.1 +/ 0.9) x 10(13) exp{(80 +/ 20)/T}, k(CF+iC4H8) = (1.1 +/ 0.1) x 10(12) exp{(400 +/ 50)/T}, k(CF+2,3dimethyl2butene) = (1.6 +/ 0.5) x 10(12) exp{(720 +/ 95)/T}, k(CF+allene) = (3.4 +/ 0.4) x 10(12) exp{(1037 +/ 100)/T}, k(CF+1,3butadiene) = (9 +/ 2) x 10(12) exp{(560 +/ 140)/T}, k(CF+isoprene) = (1.2 +/ 0.2) x 10(11) exp{(190 +/ 80)/T}, and k(CF+propyne) = (3 +/ 1) x 10(12) exp{(860 +/ 200)/T}. For the other butenes, the following rate constants were measured at T = 294 K: k(CF+1butene) = (8.28 +/ 0.83) x 10(12), k(CF+cis2butene) = (5.22 +/ 0.52) x 10(12), and k(CF+trans2butene) = (5.56 +/ 0.56) x 10(12). For the alkenes, as well as for the alkanedienes, linear correlations were observed between the Arrhenius activation energy and the ionization potential (IF) of the corresponding hydrocarbon and likewise between the Arrhenius frequency factors and the IF. Ample evidence is presented that the title reactions are electrophilic cycloaddition reactions. 
ISSN:  10895639 
Publication status:  published 
KU Leuven publication type:  IT 
Appears in Collections:  Quantum Chemistry and Physical Chemistry Section

