Kinetic and product distribution information for the pyrolysis of tetralin is reviewed and data for 23 selected low-conversion examples are compiled that cover a temperature range from 450-730 °C and a concentration range from 3.8 × 10 0 -6 × 10 -5 M (as well as one example in the shock-tube regime). The challenge in developing a mechanistic model arises from a delicately balanced competition among several product-forming pathways (ring contraction to methylindan derivatives, successive dehydrogenations, hydrogenolytic ring-opening and side-chain cracking, and expulsion of ethylene to form benzocyclobutene) that is very sensitive to temperature, concentration, and conversion level. A reaction network was formulated that involves 174 freeradical steps, 23 radicals, and 27 products. Estimated rate constants were assigned by thermochemical kinetic protocols. Predicted reaction dynamics were analyzed to understand the sources of unusual induction periods, autoacceleration kinetics, sigmoidally curved van't Hoff plots, strong dependences of product distributions on conditions, and sensitivity to 1,2dihydronaphthalene impurity. Multiple initiation, propagation, and termination pathways were deconvoluted. Predictions of note are that molecular disproportionations between tetralin and evolving products, especially 1,2-dihydronaphthalene, are a major contributor to chain initiation and that chain termination occurs largely by disproportionation of the dominant 1-tetralyl radical because its kinetically more facile combination is highly reversible. After modest adjustment of two rate constants, the average deviation of the predicted integral reaction rates from the experimental rates was only -0.07 log units (σ ) (0.41, probably largely indicative of scatter in the data set). However, a significant discrepancy remains because the bulk of the data does not support the prediction of generic autoacceleration, which arises from the involvement of products in initiation. The major product distribution patterns were well reproduced, in particular the dominance of 1-methylindan among the ring-contraction products, the increases in both the dehydrogenation/ring-contraction ratio, and the 1,2-dihydronaphthalene/naphthalene ratio (at a given conversion level) with decreasing concentration and/or increasing temperature, and the proportioning of the "H" made available by dehydrogenation between major formation of H 2 and minor operation of multiple stoichiometries for ring-opening and cracking. As currently formulated, the model does not accommodate a modest but nontrivial formation of indene observed under selected conditions, but a suggestion is made for further testing of a multistep pathway that appears to be kinetically competent to account for C 1 -loss as a primary process. No satisfying pathway has been formulated for minor formation of methylindene isomers that has been reported in one case. Finally, the model is compared with a complementary model that has been recently proposed and tested over a much more limited range of t...
