THERMAL CLEAVAGE OF THE ONE-ATOM ARYL-HYDROARYL BRIDGE IN 8-(1-NAPHTHYLMETHYL)-3,4-DIHYDRONAPHTHALENE

2-(1-Naphthylmethyl)-3,4-dihydronaphthal (NMDN) was pyrolyzed neat at temperatures between 300 and 385 degrees C for batch holding times bet ween 20 and 360 min. The products formed in the highest molar yields a t moderate conversions are 2-(1-naphthalenylmethyl)naphthalene (dinaph thylnethane), 1-methylnaphthalene, 1,2-dihydronaphthalene (dialin), an d 2-(1-naphthylmethyl)tetrahydronaphthalene (naphthyltetralylmethane). At higher conversions, 1,2,3,4-tetrahydronaphthalene (tetralin) and n aphthalene appeared as important products. The temporal variations of the products' molar yields indicated that all of the products above, s ave tetralin, were primary products. These assignments led to a NMDN r eaction network that comprises four parallel, stoichiometricelly balan ced, primary pathways. These paths lead to dinaphthyl-methane plus H-2 , to dialin plus 1-methylnaphthalene plus dinaphthylmethane, to naphth yltetralylmethane plus dinaphthylmethane, and to naphthalene plus 2-me thyldialin plus dinaphthylmethane. The kinetics of NMDN disappearance at 325 degrees C were consistent with a second-order rate law: The Arr henius parameters for the second-order rate constant, determined at te mperatures between 300 and 385 degrees C; are log A (L/(mol s)) = 8.8 +/- 1.1 and E = 36.4 +/- 3.2 kcal/mol. The observed reaction products and kinetics are consistent with a free-radical mechanism. Molecular d isproportionation generates reactive free-radical intermediates, which can then participate in chain reactions to form the observed products . The observed kinetics are consistent with two different assumptions about the rates of different elementary steps in the mechanism; One is that the molecular disproportionation step is rate controlling and th e other is that the chain reactions possess a long kinetic chain lengt h. An examination of the kinetics of NMDN disappearance, alone, is not sufficient to discriminate between these two mutually exclusive possi bilities.