Accession Number : ADA183123
Title : Zeolite-Supported Tetramethyl-1,2-Dioxetane: New Pathways to Chemiluminescence.
Descriptive Note : Technical rept.,
Corporate Author : WISCONSIN UNIV-MADISON DEPT OF CHEMISTRY
Personal Author(s) : Benedict,Bryan L ; Ellis,Arthur B
PDF Url : ADA183123
Report Date : 08 Jul 1987
Pagination or Media Count : 12
Abstract : The thermal decomposition of tetramethyl-1,2-dioxetane (TMD) sorbed into zeolite Y containing Europium ions and bipyridine (samples abbreviated as ZYEBT) has been investigated. Decomposition of TMD yields, by energy transfer processes, chemiluminescence (CL) characteristic of the Eu3+ ion. At loading levels corresponding to an upper limit average of 0.5, 1.0, and 2.0 TMD molecules per unit cell, the CL decay curves are nonexponential at short times; at longer times, roughly exponential curves are characterized by a unimolecular rate constant k. Analyses of the long-time decays based on an Arrhenius expression for the rate constant provide evidence for a kinetic compensation effect: pilots of log k vs. the activation energy as a function of TMD loading level are linear. Solution data (benzene, benzonitrile) fall on the same line, suggesting that TMD decomposes by a common rate-limiting mechanism in these various environments. The Arrhenius parameters (Ea and the pre-exponential factor A) are smaller than that solution values and increase with TMD loading. When TMD is sorbed to the extent of an upper-limit average of approximately 7 molecules per unit cell, CL decay curves are initially nearly flat and then show an increase in decomposition rate with time. Mechanistic implications of these results are discussed.
Descriptors : *CHEMILUMINESCENCE, *OXETANES, *ION EXCHANGE RESINS, *PYROLYSIS, *EUROPIUM, ACTIVATION ENERGY, ARRHENIUS EQUATION, BENZENE, DECOMPOSITION, RATES, IONS, MOLECULES, LONG RANGE(TIME), PARAMETERS, BENZONITRILES, ENERGY TRANSFER, COMPENSATION, REACTION KINETICS, METHYL RADICALS, PYRIDINES, SOLUTIONS(GENERAL), LIMITATIONS, CELLS, SHORT RANGE(TIME)
Subject Categories : Physical Chemistry
Distribution Statement : APPROVED FOR PUBLIC RELEASE