Structure-reactivity correlations in the reactions of hydrocarbons on transition metal surfaces. 1. Ring contraction of cyclooctene, 1,3-cyclooctadiene, 1,5-cyclooctadiene, and cyclooctatetraene to benzene on a platinum(111) surface

Journal Article · Thu Mar 17 00:00:00 EST 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100062a036· OSTI ID:7069455

Hostetler, M J; Nuzzo, R G; Girolami, G S ^[1]; Dubois, L H ^[2]

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1. Univ. of Illinois, Urbana, IL (United States)
2. AT T Bell Lab., Murray Hill, NJ (United States)

The adsorption and subsequent reactions of the C[sub g] cyclic hydrocarbons cyclooctane (COA), cyclooctene (COE), 1,3-cyclooctadiene (1,3-COD), 1,5-cyclooctadiene (1,5-COD), and cyclooctatetraene (COT) have been studied on a platinum(111) single crystal surface. On clean Pt(111), the majority of the adsorbed COA desorbs molecularly, whereas all of the unsaturated hydrocarbons are dehydrogenated to COT and then converted to benzene. In several cases, intermediates in the dehydrogenation pathway can be identified spectroscopically; for example, COE is dehydrogenated to COT via the diene 1,3-COD. In all cases, whether added directly to the surface or formed via dehydrogenation reactions, COT is bound to the surface initially in a tub-shaped [eta]+4 fashion and is converted to a planar [eta]+3 structure at higher temperatures. The conversion of COT to benzene follows thereafter. Co-adsorption experiments with COT and COT-d[sub 8] indicate that the majority of the benzene is formed via an intramolecular rearrangement and not by complete fragmentation of COT to acetylene followed by cyclotrimerization. We propose that, at 475 K, COT undergoes ring contraction to form bicyclo[4.2.0]-octa-1,3,5-triene (BOT). The BOT is then transformed via a retro[2 +2]cyclization to benzene, which desorbs, and acetylene, which is dehydrogenated first to surface ethynyls and then to a surface carbon overlayer. 72 refs., 14 figs., 3 tabs.

• DOE Contract Number: FG02-91ER45439
• OSTI ID: 7069455
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 98:11; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BENZENE
SYNTHESIS
CYCLOALKENES
ADSORPTION
DECOMPOSITION
DEHYDROGENATION
DESORPTION
MOLECULAR STRUCTURE
HYDROCARBONS
PLATINUM
SURFACE PROPERTIES
TRANSITION ELEMENTS
ACETYLENE
CATALYSTS
DEUTERIUM COMPOUNDS
EXPERIMENTAL DATA
MONOCRYSTALS
ALKENES
ALKYNES
AROMATICS
CHEMICAL REACTIONS
CRYSTALS
DATA
ELEMENTS
HYDROGEN COMPOUNDS
INFORMATION
METALS
NUMERICAL DATA
ORGANIC COMPOUNDS
PLATINUM METALS
SORPTION
400201* - Chemical & Physicochemical Properties
661300 - Other Aspects of Physical Science- (1992-)