Thermochemical and kinetic analysis on the addition reactions of H, O, OH, and HO2 with 1,3 cyclopentadiene

Chemical activation and unimolecular dissociation pathway and kinetic analysis is presented on addition of radicals H, O, OH, and HO2 to one of the two types of unsaturated carbons on cyclopentadiene. Addition of H atom or OH radical at the 1 position forms an allylic radical, which can break the weaker (allylic) carbon(SINGLEBOND)carbon bond, opening the 5-carbon ring and forming a resonance stabilized radical. Addition at the 2 position is less exothermic and forms a secondary radical, which can break a carbon(SINGLEBOND)carbon bond to form a vinylic radical. The vinylic radical, if formed will rapidly react with O2 or decompose, β Scission. Addition at the 2 position usually results in reverse reaction (dissociation back to the reactants) O(3P) addition to the two types of unsaturated carbons on cyclopentadiene will form two diradical isomers which will quickly decompose to H atom plus cyclopentenone-yl radicals, both of these cyclopentenone-yl radicals will undergo β Scission to form stable cyclopentadienone and H atom. HO2 addition to the unsaturated carbons on cyclopentadiene can form the cyclopentenyl (allylic) radical plus O2 as products through intramolecular isomerization (H Shift) and then dissociation. Thermochemical property data for intermediate species along with rate constants for these radical addition reactions to cyclopentadiene and the decomposition/isomerization reactions of the adducts are estimated. Rate constants for each channel are calculated using bimolecular quantum Rice Ramsperger Kassel, QRRK, for k(E) with a modified strong collision analysis for fall off. Rate constants are presented over a range of pressure and temperature. Modeling results are compared to the limited literature data available for validation, i.e., to species profiles for appropriate reaction systems, where cyclopentadiene is a key intermediate. Rate constants on abstraction of the resonance stabilized H from the cyclopentadiene ring are also estimated. Major (vida infra) reaction channels and kinetic parameters Addition at the 1 position \scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\quad$\rm #$\hfil&\qquad $\rm #$\hfil\crCY13PD+H\Longleftrightarrow C=\!=CC.C=\!=C&\it k\rm =1.4\ 10^{14}\ \it T\rm ^{-0.18}\ exp(-3150/\it RT\rm )\cr CY13PD+O\Longleftrightarrow \hbox{Cypent-3-eneone-2yl}+H&\it k\rm =8.91\ 10^{12}\ \it T\rm ^{-0.15}\ exp(-590/\it RT\rm )\cr CY13PD+OH\Longleftrightarrow C=\!=CC.C=\!=COH&\it k\rm =8.18\ 10^{12}\ \it T\rm ^{-0.07}\ exp(-850/\it RT\rm )\cr CY13PD+HO_{2}\Longleftrightarrow \hbox{Cypentene-3yl}+O2&\it k\rm =1.33\ 10^{15}\ \it T\rm ^{-1.07}\ exp(-9530/\it RT\rm )\cr} Addition at the 2 position \scriptfont4=\seveni \scriptscriptfont4=\fivei \halign{\quad$\rm #$\hfil&\qquad $\rm #$\hfil\crCY13PD+H\Longleftrightarrow C=\!=CC.+C\equiv\!\equiv C&\it k\rm =1.64\ 10^{36}\ \it T\rm ^{-5.99}\ exp(-32500/\it RT\rm )\cr CY13PD+O\Longleftrightarrow \hbox{Cypent-3-eneone-4yl}+H&\it k\rm =5.60\ 10^{12}\ \it T\rm ^{-0.06}\ exp(-200/\it RT\rm )\cr CY13PD+OH\Longleftrightarrow C=\!=CC.OH+C=\!=C&\it k\rm =1.07\ 10^{33}\ \it T\rm ^{-5.49}\ exp(-37420/\it RT\rm )\cr} Units cm-3 mole-1 sec -1, Ea in kcal/mole, temperature range 900-1400 K © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 893–913, 1997.