4095-06-1Relevant articles and documents
Crossed-beam reaction of carbon atoms with hydrocarbon molecules. II. Chemical dynamics of n-C4H3 formation from reaction of C(3Pj) with methylacetylene, CH3CCH (X1A1)
Kaiser,Stranges,Lee,Suits
, p. 8721 - 8733 (1996)
The reaction between ground-state carbon atoms, C(3Pj), and methylacetylene, CH3CCH (X1A1), was studied at average collision energies of 20.4 and 33.2 kJ mol-1 using the crossed molecular beams technique. Product angular distributions and time-of-flight spectra of C4H3 at m/e=51 were recorded. Forward-convolution fitting of the data yields weakly polarized center-of-mass angular flux distributions isotropic at lower, but forward scattered with respect to the carbon beam at a higher collision energy. The translational energy flux distributions peak at 30-60 kJ mol-1 and show an average fractional translational energy release of 22%-30%. The maximum energy release as well as the angular distributions are consistent with the formation of the n-C4H3 radical in its electronic ground state. Reaction dynamics inferred from these distributions indicate that the carbon atom attacks the π-orbitals of the methylacetylene molecule via a loose, reactant like transition state located at the centrifugal barrier. The initially formed triplet 1-methylpropendiylidene complex rotates in a plane almost perpendicular to the total angular momentum vector around the BC-axes and undergoes [2,3]-hydrogen migration to triplet 1-methylpropargylene. Within 1-2 ps, the complex decomposes via C-H bond cleavage to n-C4H3 and atomic hydrogen. The exit transition state is found to be tight and located at least 30-60 kJ mol-1 above the products. The explicit identification of the n-C4H3 radical under single collision conditions represents a further example of a carbon-hydrogen exchange in reactions of ground state carbon atoms with unsaturated hydrocarbons. This channel opens a versatile pathway to synthesize extremely reactive hydrocarbon radicals relevant to combustion processes as well as interstellar chemistry.
NEUE WEGE ZUM CYCLOBUTADIEN UND METHYLENCYCLOPROPEN
Maier, Guenther,Hoppe, Manfred,Lanz, Klaus,Reisenauer, Hans Peter
, p. 5645 - 5648 (2007/10/02)
New routes to cyclobutadiene (2) and methylenecyclopropene (4) are described.Matrix irradiation of cyclopropenylketene (9) gives cyclobutadiene.Flash pyrolysis of 8, 11, 16, 17 and 18 also generates cyclobutadiene, which can be deposited from the gas phase onto a window cooled to 10 K.Methylenecyclopropene is one of he products in the thermal fragmentation of 8 or 14.
