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Various substituted norbornenes are subjected to metal-catalysed [2 + 21 cycloadditions to yield activated cyclobutenes which react further with quadricyclane to yield linear binadienes, or with cyclopentadiene to form angular binadienes; these binadienes are rigid alicyclic frameworks available to synthetic chemists for molecular desig n .

The reaction pathways of n-butoxy and s-butoxy radicals have been investigated by TLC and HPLC analysis of end products, particularly peroxides and carbonyl compounds. The butoxy radicals were produced by the pyrolysis of very low concentrations of the corresponding dibutylperoxide in an atmosphere of oxygen and nitrogen, at atmospheric pressure. The decomposition reaction (3) s-BuO + CZHs + CHSCHO and the reaction (2) s-BuO + 0 2 ---f HOz + CH3COC2H6 have been studied, and the ratio k3/k2 has been determined in the temperature range 363-503 K by kinetic modeling of the formation of the observed acetaldehyde and methylethylketone. The rate constant kt obtained was: log,, k3/s-l = (13.8 f : : : ) -(15.0 * 0.9) kcal mo1-'/2.303 R T .A good agreement was observed between experimental data and RRKh4 theory. The implications of the results for atmospheric chemistry and combustion are discussed. At room temperature, the reaction with 02, yielding HOz radicals and methylethylketone is, by far, the main channel for s-BuO radicals. In the field of low temperature combustion, the decomposition of s-BuO radicals producing CzHS and CH3CH0 is the main pathway; the route s-BuO + 0 2 decreases tremendously in importance as the temperature is raised above 393 K.

Radical-radical recombination reactions (e.g., CH3 + CH3 C2H6) proceed with no barrier through simplefission transition states. The application of transition state theory (TST) to these reactions is discussed, achieving a new understanding of the dividing surface and dynamical assumption implicit in all TST treatments of these reactions. A reinterpretation of the modified Gorin model for such transition states is discussed which removes several inconsistencies from this model and greatly improves data prediction and interpretation for radical-radical recombination reactions (and the reverse unimolecular dissociations) in the gas phase.The suggested model is an extension of the basic Gorin approach, which treats the transition state as consisting of two moieties which have the same vibrational and rotational properties as the fully separated fragments. The method discussed here proposes an improvement of the modified Gorin model Hamiltonian that better describes simple-fission reaction dynamics by completely excluding trajectories occurring with unfavorable orientations of the combining moieties from the transition state theory rate coefficient. This new approach is sufficiently simple that the description is applicable to any system and thus can be routinely implemented with modest computational resources. Comparison with experiment and with more precise theoretical descriptions for ethane and neopentane decomposition reactions shows that this treatment provides quantitative agreement for ethane. It is also concluded that more sophisticated treatments of transitional modes than afforded by hindered rotor models are needed for the description of transition states with bulky moieties at elevated temperatures, such as the neopentane decomposition system described here.

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