The classical mechanism of chemically activated unimolecular reactions is extended to interpret experimental results in systems olefin/hydrogen atoms. In the case of a large excess of the latter, one has to take into consideration a second chemical activation of the primarily formed radicals by their recombination with H-atoms to yield chemically activated alkane molecules. The radicals as well as the alkane molecules may decompose, and a method based on the coupling of two steady-state master equations is developed to evaluate the contribution of either of the two reaction paths to the ratio decomposition to stabilization. The treatment proposed is demonstrated for the example cis but-a-ene/excess of thermal hydrogen atoms in the presence of molecular hydrogen as a bath gas at 298 K. It turns out that the step via activated butane is not negligible under these conditions.

Die mit 1 ncd 2 durcligefiihrten Experimente [Reaktortemperatur 7EO-950"C; 1 Pa KW-Partialdruck; Molverhaltnis Matrixgas (N, oder Ar): KW M 300-500; Matrixtemperatur 10 bzw. 77 K] ergabcn, daS unterhalb von 900°C IR-spektroskopisch lediglich Hinneise auf die ausschlieWliche Bildung von Methylcyclopentadienen (6G2, 680, 813, 890, 902 cm-l) erhalten werden. Bei Erhohung der Renktortemperatur auf uber 900°C weisen die Matrixspektren (vgl. Bild 1) auBerdem charakteristische IR-Banden fur [8] Masarov, I . N.; Kuznecov, N . V.: 8. obS. Chim. 29 (1959) 767[9] Ziegler, U.; Zimmermann, G.; Ondruschka, B.; Volkova, 8. V.; Gusel'nikov, L. E.; Smirnov, ?.. I.; Numetkin, N . 8.

About the Reaction of Hydrogen Atoms with Cyclopentene and Cyclohexene in the Gas Phase The reaction of hydrogen atoms with cyclopentene and cyclohexene has been investigated in an isothermal flow‐system (298 K) at a pressure of 130 Pa. 12 products of the cyclopentene reaction and 17 products of the cyclohexene reaction were identified by gas chromatography. The quantitative studies show, that the main reactions of the cyclopentene system are the hydrogenation to cyclopentane and the chemical activated decay to methane; cyclohexene reacts especially by hydrogenation to cyclohexane and ring‐isomerisation to methylcyclopentane.

The reactions of hydrogen atoms with the cycloalkenes C5 to C8 and the n‐alkenes C2 to C8 have been studied at room‐temperature in a flow system. In the presence of an excess of H‐atoms two steps of chemical activation occur: 1) the addition of H‐atoms to the double bond and ii) the combination of the radicals formed with H‐atoms. The main processes are the stabilization (S) of the activated intermediates by collisions and the decomposition (D) via ring opening and degradation. It is shown that the ratio D/S decreases with increasing concentration and size of the hydrocarbon. To calculate the ratios D/S for the first and the second activation step the classical formalism for chemically activated systems is extended. A method based on the coupling of two conventional steady‐state master equations is presented to evaluate the contribution of either of the two reaction paths. It is shown that the second way, via activated alkanes, is more important under these conditions.

About the Reaction of Atomic Hydrogen with 1‐Olefines. Chemical activated reaction paths of the C2C8‐l‐olefines, initiated by atomic hydrogen, have been studied using an isothermal flow‐system (298 K, 130 Pa) with electrical discharge. In the reaction mixtures homologeous series of 1‐olefines and n‐alkanes were found which are identical with those of cycloolefine systems described previously [1, 2]. The reactions of the 1‐olefines are analysed and discussed in detail and compared to the cycloolefine reactions.