Reactive intermediates in the interconversions of C3H4 hydrocarbons

Steinmetz, Mark G.; Srinivasan, R.; Leigh, William J.

doi:10.1007/bf03155645

Cited by 33 publications

(16 citation statements)

References 75 publications

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“…In the parent (C3H4) system, the ground state of vinylmethylene is the planar vinyl-diradical (up) triplet state (9-15, 35), but the two lowest excited singlet states, the carbenic u2 and higher energy up (vinyl-diradical) states, are thought to be the ones normally obtained in thermal or photochemical ring opening of cyclopropenes (3). Calculations reveal that the ground state of cyclopropene correlates with the vinylmethylene up state, while the first excited singlet state correlates with the lower energy u2 state (9-15).…”

Section: Discussionmentioning

confidence: 99%

“…that typical of arylcyclopropenes. These compounds afford substantial amounts of allene and alkyne products in addition While the photochemistry of arylcyclopropenes has thus been to the 1,3-dienes and other products that are characteristic of , extensively investigated (1)(2)(3)(4)(5)(6)(7)(8), there have been few reported vinylcarbene intermediates. The photochemistry of compounds ' studies of simple alkyl-substituted derivatives in solution and supplements the elegant studies of Steinmetz er (I6, 19), probably because the parent chromo~hOre is devoid Of (16)(17)(18) and Johnson and co-workers (19)(20)(21) on the photoabsorption above 210 nm and hence requires the use of ,-hemistry of allene derivatives.…”

Section: + A+a+m+mentioning

confidence: 99%

“…[3]) may provide an important photochemical decomposition pathway in simple cyclopropenes with high singlet excitation energies (14). Carbene photoextrusions are rather common in cyclopropane photochemistry (23,24) (particularly in alkyl-substituted systems) (24), but have apparently not been observed in cyclopropene systems.…”

Section: + A+a+m+mentioning

confidence: 99%

“…. pene to propyne (3,25) may proceed by G o competitive pathways (eq. [4]), one involving [1,2]-H migration in vinylmethylene and the other involving the intermediacy of propenylidene (15).…”

Section: + A+a+m+mentioning

confidence: 99%

“…20% conversion, and identified by ir and 'H/I3C nmr spectroscopy and gc/ms analysis, and comparisons to literature data in the cases of 11 and 12. Relative product yields were determined by a similar method to that used for the photolysis of 3 We have ruled out sequential two-photon excitation by the laser as contributing to the observed photochemistry for either Reaction quantum yields were not determined quantitatively, but they appeared to be quite low on the basis of qualitative comparisons to other systems that we have studied under similar conditions (32). We thus estimate the upper limit for the quantum yields of disappearance of 3 and 4 to be in the range 0.01-0.1.…”

Section: 33-trimethylcyclopropenementioning

confidence: 99%

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The far-ultraviolet photochemistry of alkylcyclopropenes in solution

Fahie¹,

Leigh²

1989

Can. J. Chem.

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This paper is dedicated to Professor Ronald J . Gillespie on the occasion of his 65th birthday BRIAN J. FAHIE and WILL~AM J. LEIGH. Can. J. Chem. 67, 1859Chem. 67, (1989. The photochemistry of 1,3,3-trimethylcyclopropene and 1-tert-butyl-3,3-dimethylcyclopropene has been investigated in hydrocarbon, methanol, and 1-hexene solution with far-ultraviolet (185-228 nm) light. Direct photolysis of the two compounds affords allene, alkyne, and 1,3-diene derivatives, formally as a result of initial bond cleavage to yield vinylcarbene intermediates. Products derived from cleavage of the most substituted (Cl-C3) cyclopropene bond account for 60-80% of the observed mixture in each case. Results from the photolysis of 1 ,3,3-trimethylcyclopropene-1-13C suggest a second pathway for formation of alkyne products in cyclopropene photochemistry, which occurs in competition with (or by exclusion of) the vinylcarbene

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Section: Discussionmentioning

confidence: 99%

Section: + A+a+m+mentioning

confidence: 99%

Section: + A+a+m+mentioning

confidence: 99%

Section: + A+a+m+mentioning

confidence: 99%

Section: 33-trimethylcyclopropenementioning

confidence: 99%

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The far-ultraviolet photochemistry of alkylcyclopropenes in solution

Fahie¹,

Leigh²

1989

Can. J. Chem.

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Bequeme Synthese von Vinylcyclopropanen durch intermolekularen Abfang von thermisch erzeugtem Perchlorvinylcarben

Weber

Meijere

1985

Chem. Ber.

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Tetrachlorcyclopropen (I) wird oberhalb 150°C ringgeijffnet zu Perchlorvinylcarben (2), welches sich mit hoher Effizienz intermolekular an Olefine addiert. In den Produkten, 1-Chlor-1-(trichlorviny1)cyclopropanen 7, 11 bzw. 14, bleibt die Olefinkonfiguration erhalten. Mil n-Hexan und Adamantan entstehen durch C -H-Insertion Convenient Synthesis of Vinylcyclopropanes by Intermolecular Trapping of Thermally Generated Perchlorovin ylcarbeneTetrachlorocyclopropene (1) is ringopened above 150°C to give perchlorovinylcarbene (2), which is intermolecularly trapped by olefins with high efficiency. The olefin configuration is retained in the products, 1-chloro-I-(trichloroviny1)cyclopropanes 7, 11, and 14, respectively. With n-hexane and adamantane 17 -19 as well as 21 and 22 are obtained by C -H insertion. For 21 olefins with different degrees of substitution and types of substituents the isolated yields range from 24 LO 88%, in most cases above 60%. Acrylonitrile (9%) and substituted acrylonitriles (17%) give lower yields, acrylates, however, react well. The torsional barriers of the chloro(trichlorovinyI)cyclopropane derivatives 14 are unusually high (17.4 -18.6 kcal/niol) for vinylcyclopropane systems. Products 7 can be reductively dechlorinated to vinylcyclopropane hydrocarbons 23, ethylidenecyclopropanes 24 being observed as by-products.Cyclopropene konnen therrnisch oder photolytisch zu Vinylcarbenen ringoffnen 1*2). Jedoch fand die umgekehrte Reaktion, die Cyclisierung aus anderen Vorstufen erzeugter Vinylcarbene, als synthetischer Zugang zu Cyclopropenen lange Zeit groljere Beachtung3). Zwar gibt es eine Vielzahl von Cyclopropen-Ringdffnungsreaktionen4*'), bei d e nen Vinylcarbene als Zwischenstufe postuliert wurden, doch nur wenige, bei denen diese intermolekular an Doppelbindungen addiert werden. Auch bei der triplettsensibilisierten Photolyse6) und der durch Kupfersalze katalysierten') Zersetzung von Vinyldiazomethan in Gegenwart von Olefinen uberwiegen intramolekulare Reaktionen wie 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1985

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Gas phase kinetics of pyrolysis of 1‐methyl‐1‐cyclopropene

1985

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The title study has been carried out in the temperature range 210-250°C. The isomerisation products are 2-butyne (91 -94%), 1,3-butadiene (5-8%), and 1,Zbutadiene (1 -2%). No other products were detected and material recovery was complete within experimental error (+ 5%). The reaction obeyed first-order kinetics, with the products formed by parallel pathways, and appeared to be both unimolecular and homogeneous although some surface sensitivity was detected in packed vessels. Studies of pressure dependence showed characteristic rate constant "fall-off' below 20 Torr (SF,) and 100 Torr (Nz). Within at least 2% of the high pressure limit, the following Arrhenius equation for overall decomposition wasArrhenius equations were similarly found for the individual pathways. The figures are discussed in the light of Transition State Theory and represent a significant improvement over a previous study. It is argued that all products arise via 1,2-H shifts in a diradical-like intermediate and the propensities for different H shifts are discussed. A 1 -methyl substituent, rather surprisingly, deactivates cyclopropene in its isomerisation reactions. Die Gasphasenkinetik der Pyrolyse yon 1-Methyl-1-cyclopropn')Die Pyrolyse von I-Methyl-I-cyclopropen wurde im Temperaturbereich von 210 -250 "C untersucht. Als Isomerisierungsprodukte wurden 2-Butin (91 -94%), 1,3-Butadien (5 -8%) und 1,2-Butadien (1 -2%) nachgewiesen; andere Produkte entstehen bei vollstandiger Materialbilanz ( * 5% Abweichung vom berechneten Wert) nicht. Die Reaktion verlauft nach einem Zeitgesetz 1. Ordnung, wobei die isomeren Produkte in parallelen Reaktionswegen gebildet werden. Die Umlagerungen erfolgen unimolekular und homogen, obwohl in gepackten ReaktionsgefaDen eine gewisse Oberflachenabhangigkeit beobachtet wurde. Charakteristisches "fall-off'-Verhalten tritt in Gegenwart von SF6 unterhalb von 20 Torr, in Gegenwart von N2 unterhalb von 100 Torr ein. Die Gesamtreaktion laBt sich innerhalb des Hochdruckbereichs durch die folgende Arrhenius-Gleichung beschreiben:

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Reactive intermediates in the interconversions of C3H4 hydrocarbons

Cited by 33 publications

References 75 publications

The far-ultraviolet photochemistry of alkylcyclopropenes in solution

The far-ultraviolet photochemistry of alkylcyclopropenes in solution

Bequeme Synthese von Vinylcyclopropanen durch intermolekularen Abfang von thermisch erzeugtem Perchlorvinylcarben

Gas phase kinetics of pyrolysis of 1‐methyl‐1‐cyclopropene

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