1517-51-7Relevant academic research and scientific papers
Deceptive Similarities in the Reactions of Fe+ and Co+ with Linear Nitriles in the Gas Phase
Lebrilla, Carlito B.,Drewello, Thomas,Schwarz, Helmut
, p. 5639 - 5644 (2007/10/02)
The gas-phase reactions of the transition-metal ions Fe+ and Co+ with linear C(4)-C(12) nitriles are reported.In spite of an overall similar reactivity pattern, a more detailed analysis, based on the study of labeled nitriles, reveals distinct differences with regard to the mechanisms of elimination of alkenes and alkanes.For both metal ions, hydrogen and alkenes are generated from linear C(4)-C(12) nitriles, and the intermediates are formed via oxidative addition to terminal and internal C-H bonds.For the RCN/Fe+ system insertion in an internal C-H bond commences at position C(8) of the nitrile; for the analogous RCN/Co+ system, the oxidative addition to an internal C-H bond starts at position C(7) of the nitrile.Similarly, alkane formation is different for the two transition-metal ions.For RCN/Fe+ the generation of alkanes is observed for nitriles having at least eight carbon atoms; in contrast, the elimination of alkanes from RCN/Co+ is already observed for C(6) nitriles.Alkane elimination seems to follow the conventional mechanism (i.e., oxidative addition to a C-C bond, β-hydrogen transfer, and reductive elimination) for the RCN/Co+ system, whereas for the RCN/Fe+ complex there exists an additional mechanism.This mechanism corresponds to the loss of H2 from an internal position of the alkyl chain followed by the elimination of an alkene.Some possible origins of the different behavior of Fe+ vs.Co+ are discussed.
REACTIONS OF 2-METHYLPROPENE AND OTHER ALKENES ON ZINC OXIDE
Brown, Ronald,Kemball, Charles,Taylor, Duncan
, p. 2899 - 2914 (2007/10/02)
Studies have been made on the hydrogenation, deuteration and exchange with deuterium of ethene, propene and 2-methylpropene on zinc oxide and Arrhenius parameters for the reactions have been determined.Some general conclusions are reached about the catalytic behaviour of alkenes on zinc oxide from these and earlier results.Exchange occurs readily with alkenes which can dissociate to allyl intermediates but can also take place via the formation of vinyl intermediates with other alkenes, particularly at higher temperatures.Similar rates of alkane formation are found with different alkenes at temperatures at which the strengths of adsorption of the alkene are equivalent.The mechanism of alkane formation does not contribute to exchange of the alkene nor give rise to double-bond movement and the probable rate-determining step is the formation of adsorbed alkyl species which are then rapidly converted to alkane.
The Collisionally Induced Dissociation of Allyl and 2-Propenyl Cations
Burgers, Peter C.,Holmes, John L.,Mommers, Alexander A.,Szulejko, Jan E.
, p. 596 - 600 (2007/10/02)
Pure (1+) and CH3C(1+)=CH2 ions are generated only in metastable fragmentations of 1+., X=Cl, Br, I, and 1+., X=Br, I, respectively.For ion source generated (1+) ions there is some structural interconversion.The structure characteristic feature of their collisional activation mass spectra is the ratio m/z 27 (1+):m/z 26 (1+.).For CH3C(1+)=CH2 the ratio is only weakly dependent upon the translational energy of the ion.For (1+), the ratio rises sharply as translational energy is reduced, from 0.9 at 8 kV to c. 3 at 1 kV. (1+) ions generated by charge reversal of (1-) show higher ratios, resulting from their lower average internal energy content.It must therefore be emphasized that (1+) ion structure assignments should only be made using reference data which apply to specific experimental conditions. (1+) daughter ion structures for a number of well-known fragmentations have been established.The heat of formation of the 2-propenyl cation was measured to be 969+/-5 kJ mol-1.Labelling experiments show that at low internal energies, allyl cations do not undergo atom randomization in c. 1-2 μs; high internal energy ions of longer lifetime (c. 8 μs) show complete atom randomization.H1+ atom loss from +. has been shown to generate (1+) and 13CH2=C(1+)-CH3 without any skeletal rearrangement.
Use of Simple Test Reactions to Characterise the Catalytic Activity of a Commercial CoO-MoO3-Al2O3 Catalyst
John, Christopher S.,Williamson, James G.,Kennedy, Lois V. F.,Tyler, J. Kelvin
, p. 1356 - 1365 (2007/10/02)
Exchange of thiophene with D2 and reactions of deuterium-labelled propene and isobutene, followed using a combination of mass spectometry and microwave spectroscopy, have been used to characterise the catalytic nature of a commercial CoO-MoO3-Al2O3 (CMA) catalyst.The results indicate that the activity of partially sulphided CMA, produced by exposure to H2S or by hydrodesulphurization (h.d.s.) of ethanethiol, closely resembles that of unsupported MoS2.Thus, sulphided-CMA shows high selectivity/activity for exchange of the α hydrogens in thiophene and catalyses double bond migration in propene through half-hydrogenated intermediates, activity characteristic of MoS2, whereas oxide-CMA is much less active for α exchange and shows Lewis acid type activity for the latter reaction.It appears that a CMA catalyst during h.d.s. may usefully be described as "dual-functional", with MoS2 supported on, and stabilised by, an acidic support.
