Crossed-beam reaction of carbon atoms with hydrocarbon molecules. I. Chemical dynamics of the propargyl radical formation, C{sub 3}H{sub 3} ({ital X}{sup 2}{ital B}{sub 2}), from reaction of C({sup 3}{ital P}{sub {ital j}}) with ethylene, C{sub 2}H{sub 4}({ital X}{sup 1}{ital A}{sub {ital g}})
- Department of Chemistry, University of California, Berkeley, California 94720 (United States)
The reaction between ground-state carbon atoms, C({sup 3}{ital P}{sub {ital j}}), and ethylene, C{sub 2}H{sub 4}({ital X}{sup 1}{ital A}{sub {ital g}}), was studied at average collision energies of 17.1 and 38.3 kJmol{sup {minus}1} using the crossed molecular beams technique. Product angular distributions and time-of-flight spectra of {ital m}/{ital e}=39 were recorded. Forward-convolution fitting of the results yields a maximum energy release as well as angular distributions consistent with the formation of the propargyl radical in its {ital X}{sup 2}{ital B}{sub 2} state. Reaction dynamics inferred from the experimental data indicate two microchannels, both initiated by attack of the carbon atom to the {pi}-orbital of the ethylene molecule via a loose, reactant like transition state located at the centrifugal barrier. Following {ital C}{sub {ital s}} symmetry on the ground state {sup 3}{ital A}{double_prime} surface, the initially formed triplet cyclopropylidene complex rotates in a plane roughly perpendicular to the total angular momentum vector around its {ital C}-axis, undergoes ring opening to triplet allene, and decomposes via hydrogen emission through a tight transition state to the propargyl radical. The initial and final orbital angular momenta {bold L} and {bold L}{prime} are weakly coupled and result in an isotropic center-of-mass angular distribution. A second microchannel arises from A-like rotations of the cyclopropylidene complex, followed by ring opening and H-atom elimination. In this case, a strong {bold L}-{bold L}{prime} correlation leads to a forward-scattered center-of-mass angular distribution. The explicit identification of C{sub 3}H{sub 3} under single collision conditions represents a single, one-step mechanism to build up hydrocarbon radicals. (Abstract Truncated)
- Research Organization:
- Lawrence Berkeley National Laboratory
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 388177
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 19 Vol. 105; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Crossed-beam reaction of carbon atoms with hydrocarbon molecules. III: Chemical dynamics of propynylidyne (l-C{sub 3}H; X{sup 2}{Pi}{sub j}) and cyclopropynylidyne (c-C{sub 3}H; X{sup 2}B{sub 2}) formation from reaction of C({sup 3}P{sub j}) with acetylene, C{sub 2}H{sub 2}(X{sup 1}{Sigma}{sub g}{sup +})
Crossed-beam reaction of carbon atoms with hydrocarbon molecules. IV. Chemical dynamics of methylpropargyl radical formation, C{sub 4}H{sub 5}, from reaction of C({sup 3}P{sub j}) with propylene, C{sub 3}H{sub 6} (X{sup 1}A)