The Thermal Decomposition of trans-1,2-Dimethylcyclobutane<sup>1,2</sup>

Gerberich, H. R.; Walters, W. D.

doi:10.1021/ja01485a003

Cited by 42 publications

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“…Assuming a concerted [,2, + ,2,]-cycloreversion the substituents R or phenyl can avoid steric interactions with the oxygen atoms in a transition state analogous to 11 by slight deformation of the trans-orientation 39 whereas no such leeway is available in the cis-configuration 38[59'. 36 …”

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confidence: 99%

[2 + 2]‐Cycloreversions

Schaumann¹,

Ketcham²

1982

Angew. Chem. Int. Ed. Engl.

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Four-membered rings can be cleaved thermally, photochemically, or catalytically into two n: bonded fragments. Theoretical calculations, kinetic studies, and investigations of stereoand regioselectivity have been undertaken to clarify the question of whether the reaction involves one or two steps and to permit predictions on its course. [2 + 2]-Cycloreversions have been used to clarify the structure of four-membered rings, to prepare highly reactive n: electron-systems and-in combination with a [2 + 2]-cycloaddition-t0 protect double bonds.The combination of a cycloaddition and -reversion can be used to convert a carbonyl group into an olefin. Starting with compounds containing annelated four-membered rings, compounds with two functional groups or large ring systems can be prepared. (2 + 2]-Cycloreversions have also been discussed in connection with storage of solar energy. 3 5 We will classify a reaction as a [2+2]-cycloreversion only when two opposing o bonds of a carbo-or heterocyclic four-membered ring 3 are cleaved to give 112 or 4/5.Other terms used in the literature, "retrograde [2 + 21-cycloaddition", and "[4+2 + 2]-cycloelimination" are synonymous with [2 + 2]-cycloreversion. On the other hand, the concept "metathesis" has come to be used for the disproportionation of alkenes catalyzed by transition-metal compounds (cf. Section 4.1).If in 1-5, a/d and b/c are identical then the educts and products of the overall reaction of 112 to give 4/5 belong to the same chemical type, and only an exchange of substituents occurs. This specific type of cycloaddition and cycloreversion has been called an "exchange reaction" by Ul-The complete reaction often takes place in situ Angew. Chem. Inr. Ed. Engf. 21 (1982) 225-247 0 Verlag Chemie GrnbH, 6940 Weinheirn. 1982 0570-0833/82/0404-0225 S 02.50/0 Mechanism of 12 + 21-CycloreversionsAccording to the principle of microscopic reversibility the same considerations for the reaction mechanism must apply to the [2 + 2]-cycloreversion as to the [2 + 21-cycloaddition. If the two o-bonds are broken simultaneously, then according to the Woodward-Hoffmann rules['] for a thermally induced cleavage this corresponds to a [,2, + 02J process having transition state 11 in which the fragments separate from each other in a "corkscrew"[51 motion. A geometrically more favorable [,2, + ,2,]-reaction path via transition state l2[I4] is thermally "forbidden" i. e. would be associated with a much higher activation energy. In the case of photochemical [2 + 2]-cycloreversions the reverse relationships are expected, i. e. 12 would be favored over ll"].

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confidence: 99%

[2 + 2]‐Cycloreversions

Schaumann¹,

Ketcham²

1982

Angew. Chem. Int. Ed. Engl.

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“…A symmetry correction of R In 3 for each methyl group was applied to the calculation of the standard entropy. The 1,2-dimethylcyclobutane isomer was chosen because its rate constant for decomposition has been measured [4], while the decomposition of 1,3-dimethylcyclobutane has not been studied. The thermodynamic and kinetic properties of the latter are very likely similar to those for 1,2-dimethylcyclobutane, so that the constants for formation of either isomer are probably very close.…”

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confidence: 99%

“…2C,H4 -+ cyclobutane (4) to calculation. For completeness, the following cross-combination reactions have been included : (6) C2H4 + C,H, -C,H5 + C3H5…”

Section: Introductionmentioning

confidence: 99%

Mechanism of the bimolecular reactions of ethylene and propylene

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1970

Int J of Chemical Kinetics

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Rate constants for the bimolecular reactions of ethylene and propylene to form radicals and to form cyclobutane or its derivatives have been calculated using thermodynamic and kinetic data. Comparison of these rates with the kinetics of the thermal reactions of ethylene and propylene show that cyclobutane and its derivatives are probably not important intermediates in the processes forming radicals.

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“…The dimerization of olefins to give derivatives of cyclobutane and the reverse decomposition of cyclobutanes have been interpreted in terms of the latter path-the intermediate formation of a biradicaI [2]. The analysis of the kinetics of the decomposition reactions by O'Neal and Benson [3] has shown that the observed activation energies and frequency factors can be adequately accounted for by the properties of the biradical.…”

Section: Introductionmentioning

confidence: 99%

The cycloaddition of ethylene to butene‐2. II. Energy relations

Scacchi

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1977

Int J of Chemical Kinetics

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The rate of the thermal cycloaddition of ethylene to cis-and trans-butene-2 has been measured a t 663, 678, 693, and 703"K, and the energy relations between the reactants, intermediates, and products have been determined. The intermediate biradicals formed from the cis reactants and from the trans reactants were shown to be separated by a small but measurable enthalpy difference. This result further supports the conclusion of Part I that the intermediates are distinct species which retain some of the original configuration of the reactant. The significance of the results in relation to the mechanism of "forbidden"reactions is discussed.

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The Thermal Decomposition of trans-1,2-Dimethylcyclobutane^1,2

Cited by 42 publications

References 1 publication

[2 + 2]‐Cycloreversions

[2 + 2]‐Cycloreversions

Mechanism of the bimolecular reactions of ethylene and propylene

The cycloaddition of ethylene to butene‐2. II. Energy relations

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The Thermal Decomposition of trans-1,2-Dimethylcyclobutane1,2

Cited by 42 publications

References 1 publication

[2 + 2]‐Cycloreversions

[2 + 2]‐Cycloreversions

Mechanism of the bimolecular reactions of ethylene and propylene

The cycloaddition of ethylene to butene‐2. II. Energy relations

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The Thermal Decomposition of trans-1,2-Dimethylcyclobutane^1,2