Journal Articles (before-1995)

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    Fragmentation and Isomerization of [(CH3)2CHCHCH3]: Ions in Gas-phase Radiolysis
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (08), 1978) Collin, Guy J.; Herman, Jan A.
    A study has been made of the influence of different additives on the radiolysis of gaseous mixtures of hydrogen, 3-methyl-but-1-ene and oxygen. In these systems the [(CH3)2CHCHCH3]+ ion is formed by proton transfer from the XH+ ion to the olefin. For X = H2 the secondary pentyl ion is formed with sufficient internal energy to decompose, producing mainly ethylene. When X is CO2, CH4, N2O or CO the secondary pentyl ion partially isomerizes into the tertiary pentyl ion. This isomerization has been investigated in the mixture of xenon, methane, 3-methyl-but-1-ene and nitric oxide between –10 and + 110°C. If it is assumed that the rate of isomerization (internal hydride-ion displacement) is a function only of the temperature, the measured activation energy of the process [(CH3)2CHCHCH3]+→[(CH3)2CCH2CH3]+ is Ea= 8.8 ± 0.4 kJ mol–1(2.1 ± 0.1 kcal mol–1 or 0.092 ± 0.005 eV).
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    CO2 Poisoning of the ^'-Alumina-catalyzed Reaction of COS with SO2
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (3), 1973) Chuang, T. T.; Lana, I. G. Dalla; Liu, C. L.
    The isomerization reaction of 3,3-dimcthylbut-l-cnc (1), to produce 2,3-dimcthylbut-l-cnc (11) and 2,3-dimethylbut-2-cne (111), has been investigated over a series of copper-exchanged X-type zeolites. The reaction is believed to proceed via carbonium ion intermediates and the ability of the copper zeolites to exhibit acidic-type behaviour was demonstrated. The results emphasized the important role that the copper cations play in the reaction, and the intermediate formation of a hydrocarbon copper complex was postulated. The observed poisoning effect of water was explained in terms of the preferential formation of a copper-aqua complex. The isomerization of II was shown to be a more facile process. The exchange reactions of I and II, with deuterium oxide and deuterium, were examined over one of the copper-containing zeolites. Substantial exchange was only observed under conditions where isomerization also took place. With deuterium oxide, the exchange of I was multiple in character whereas that of II was stepwise. These differences were rationalized in terms of the relative rates of desorption of II and III from the surface and the rate of formation of a tertiary carbonium ion from the initial olefin. The exchange reactions of the olefins with deuterium all occurred via a stepwise process.
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    Homogeneous Catalysis by Pt(Il)-Sn(II) Chloride Complex: Part 2.—Mechanism of the Isomerization of n-Butenes
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (5), 1972) Hirabayashi, Kazuo; Saito, Shuji; Yasumori, Iwao
    The mechanism of the isomerization of n-butencs catalyzed by a methanolic solution of Pt(II)- Sn(II) chloride complex has been studied by kinetic, mass-spcctromctric and microwave-spectro scopic measurements. This isomerization proceeds in the presence of hydrogen. The initial rate of isomerization of 1-butcnc is of half-order with respect to hydrogen and of first-order with respect to 1-butene in the temperature range 0-20’C and total pressures up to 100 Torr. The deuterium distributions in reactants and products have been measured at 20°C in C4H84-D^-f-CH3OD systems. It was found that cis-CH2DCH=CHCH3 and cis-CH3CD=CHCH3 arc formed from 1-C4H8 and trans-2-C4H8, respectively, and CH2=CHCHDCH3 is produced from both cis- and trans-2-C4H8, and that “ simple exchange reaction ” of 1-C4H8 proceeds faster than the isomcrizations, while those of 2-butcnes scarcely occur. Double-bond migration and “ simple exchange reaction ” of propylene in the C3H64-D24-CH3OD system have been studied for comparison with those of n-butene isomerization. Hydrogen atoms in propylene exchanged with different rates depending on their positions. On the basis of these results, a detailed mechanism is proposed, which involves coordination of olefins to platinum hydride complex, formation of alkyl-platinum, and regeneration of olefins.
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    Quenching and Isomerization in the Photolysis of trans-But-2-ene and cis-Pent-2-ene at 185 nm and 203 nm
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (2), 1972) Borrell, Peter; Cervenka, A
    Additional results on the effect of additives on the product yields in the vapour-phase photolysis of trans-but-2-ene and cis-pent-2-ene are reported. They confirm, extend and reconcile our previous results with those of Chesick. The main photoreaction could be quenched by all additives at both wavelengths; at 203 nm, and with some additives at 185 nm, quenching was accompanied by photoisomerization. The effects can be correlated with the two states, Rydberg and V(π→π*), which are excited at the two wavelengths. Collisional deactivation of the V state results in photoisomerization while when the R state is deactivated no isomerization occurs. Apparently there is no ready collisional interconversion of the R and V states.