PHOTODISSOCIATION OF TERT-BUTYL HYPOCHLORITE AND DECOMPOSITION OF THETERT-BUTOXY RADICAL FRAGMENT

The photochemistry of tert-butyl hypochlorite (TBOCl) has been studied in a molecular beam by photofragment translational spectroscopy. Afte r laser excitation at 248 or 308 nm, the TBOCI molecule decays exclusi vely into a tert-butoxy radical (TBO) and a Cl atom. The photolysis at 248 nm releases almost-equal-to 60% of the available energy into the photofragment recoil which is highly anisotropic (beta = 1.9 +/- 0. 1) , implying a direct dissociation mechanism and an electronic transitio n dipole moment mu over arrow pointing right in the parent molecule th at is oriented along the O-Cl bond. Approximately 90% of the nascent T BO radicals formed at 248 nm have sufficient internal energy to underg o a secondary decay into methyl radicals and acetone, while at 308 nm TBO is stable. From a comparison of the time-of-flight distributions o f the primary fragments Cl and TBO and on the basis of the dissociatio n energy D0(1)(TBO - Cl) = 50 kcal/mol of the primary reaction, the th reshold energy for the unimolecular decay of TBO is found to be E0 = 2 0 +/- 3 kcal/mol, a value which is higher than the previously reported gas kinetic activation energy E(a) = 15 kcal/mol.