Mechanism of the Cope rearrangement

Dewar, Michael J. S.; Jie, Caoxian

doi:10.1021/ja00254a001

Cited by 72 publications

(18 citation statements)

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“…However, some years later, Osamura et al [22] published M C S C F /~-~~G ab initio calculations for the rearrangement of 1 that, they claimed, showed the ARO path to be preferred, the lengths of the breaking and forming CC bonds in the TS corresponding to the values expected for the ARO mechanism. Since the semiempirical approach had in the meantime been strengthened by the development of AM^, we reinvestigated the matter by carrying out AM^ calculations [23] for the rearrangement of 1 and for the rearrangements of 10 derivatives of 1, all of which had been studied experimentally. We also calculated secondary deuterium kinetic isotope effects (SDKIE) for the three cases (1 and its 2-phenyl and 2,5-diphenyl derivatives) for which experimental results were available.…”

Section: The Cope Rearrangementmentioning

confidence: 99%

The semiempirical approach to chemistry

Dewar¹

1992

Int J of Quantum Chemistry

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Two kinds of quantum mechanical treatment are needed in chemistry: First, a treatment accurate enough to provide definitive solutions of chemical problems, in particular, the prediction of reactions and reaction mechanisms, without reference to experiment. As yet, treatments of this degree of accuracy are restricted to a few small atoms and molecules. Second, a treatment that chemists can use as a practical aid to their own research, on the same basis as mass spectrometry or NMR. Here, the need has been largely met by the series of progressively better semiempirical methods, in particular, those developed by our group. Since only the best and most expensive ab initio procedures are superior to ours and since the computing time they need is far greater, their use as a practical aid in chemistry is restricted. Our procedures, therefore, serve as a useful supplement to ab initio ones in areas where the latter cannot be applied effectively, as the leading ab initioists now fully recognize. Since the semiempirical approach is capable of almost unlimited further development, this situation is likely to continue in the foreseeable future. 0 1992 John Wiley & Sons, Inc.

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Section: The Cope Rearrangementmentioning

confidence: 99%

The semiempirical approach to chemistry

Dewar¹

1992

Int J of Quantum Chemistry

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“…He criticized our calculations in a paper that described his own AM1 study of the Cope rearrangement [46]. Dewar and Jie's AM1 calculations found a much shallower well for cyclohexane-l,4-diyl than Dewar's MIND0/3 calculations had, and Michael even conceded that this intermediate might even turn out to be the TS for a concerted Cope rearrangement.…”

Section: Results Of' Mindois Casscf Und Am1mentioning

confidence: 95%

Symmetry breaking, diradicals, and Coping with and Coping without Ernest Davidson

Borden

2002

Molecular Physics

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This paper describes a collaboration between Professor Ernest Davidson and the author, which began in 1976 and lasted until Ernest left the University of Washington in 1984. During those 9 years we co-authored a total of 34 papers that described the results o f ah iriirio calculations on a variety of different types of organic molecules, These included antiaromatic annulenes, carbanions, carbenes, conjugated radicals and radical cations, and nonKekle hydrocarbon diradicals. Our collaboration led to insights about symmetry breaking, both real and artefactual, which formed the basis for a frequently-cited review article on this subject that we co-authored. However, our most often-referenced paper was concerned with predicting the sizes and signs of the singlet-triplet splittings in diradicals, based on whether OJ not the non-bonding Huckel molecular orbitals of a diradical can be chosen so that they are confined to disjoint sets of atoms. In 1984, we co-authored a paper on the Cope rearrangement. Since then, we have both continued to publish papers on this interesting reaction. but independently, rather than together. The results of the calculations that we each performed on the Cope rearrangement and how this reaction is affected by radical-stabilizing substituents are described. Our independent discoveries, that calculations beyond the CASSCF level are necessary in order to describe correctly the transition structure for the Cope rearrangement, led to our most recent joint publication, a 1996 review on the general importance of including dynamic correlation in ab initio calculations

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“…The resonance energy in benzene is 83X6 kJ mol À1 103X2 kJ mol À1 in the full-VB calculation) 1 . The spin weights (in percent) of W VB are shown in the ®rst row of Table 3: 1 4 40X1Y 2 3 6X8Y and 5 6X2.…”

Section: Resultsmentioning

confidence: 99%

“…Our next goal is to perform constrained SC calculations along slices of the g 2h chair and g 2v boat surfaces in order to see the fraction of diradical versus aromatic character along the interallylic distance 1 3 .…”

Section: Discussionmentioning

confidence: 99%

Transition states in modern valence-bond theory: application to the Cope rearrangement

Oliva¹

1999

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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Modern valence-bond theory, in its spincoupled form, is used to study the electronic structure of the transition structures in the Cope rearrangement. It is found that the transition structure described by à`c hair'' geometry with a``6-in-6'' CASSCF/6-31G* wave function is clearly aromatic while the CASSCF/ 6-31G*``boat'' transition structure corresponds more closely to two weakly interacting allyl radicals. Moreover, there is a striking resemblance between the CASSCF chair transition structure and the benzene molecule, arising from the modern valence-bond analysis in terms of Rumer spin functions. In agreement with previous works, dynamical correlated wave functions show shorter interallylic distances in the optimized transitions structures. The use of spin-coupled wave functions on the latter geometries results in diradical and aromatic character for the chair and boat transition structures, respectively.

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Mechanism of the Cope rearrangement

Cited by 72 publications

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The semiempirical approach to chemistry

The semiempirical approach to chemistry

Symmetry breaking, diradicals, and Coping with and Coping without Ernest Davidson

Transition states in modern valence-bond theory: application to the Cope rearrangement

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