High pressure (4+2) cyclodimerisation of 2,3-dimethyl 1,3-butadiene possible competition between concerted and stepwise mechanisms

Jenner, G.; Rimmelin, J.

doi:10.1016/s0040-4039(00)77401-6

Cited by 15 publications

(7 citation statements)

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“…The ene reaction has also received attention and the reaction of ( 6) with (7) exemplifies the existence of a generally tight, product-like transition An exception to this pattern appears to be the dimerization of 2,3-dimethylbuta-1,3diene (8). 34 In this case the volume of activation is considerably less negative than the volume of reaction, suggesting a transition state which does not lie close to products. The entropy of activation is correspondingly less negative than usual ( -28 cal K-' mol-' compared to -41 for isoprene dimerization).…”

Section: Ph'mentioning

confidence: 86%

Chapter 2. Physical methods. Part (iii) High-pressure chemistry

Isaacs¹

1981

Annu. Rep. Prog. Chem., Sect. B

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With some 60 groups carrying out aspects of chemistry at pressures in the kbar range, this topic must be regarded as one of major importance. Two principal objectives may be sought in carrying out reactions under pressure in solution. Rates may be measured as a function of pressure and the volume of activation, AV*, obtained according to equation (1) (AV* is defined as the difference in partial molar volumes of the transition state and reagents).* This is most usefully combined with a measurement of the overall volume change for the reaction to give a 'volume profile', which is proving to be a unique probe into the nature of the transition state. A similar relationship holds for equilibria, equation ( 2) where A V is the volume change for the reaction. Pressure will therefore favour a process that involves a diminution in volume, and conversely. The other aspect of interest is to employ this principle for preparative chemistry in order to bring about reactions that have a large, negative value of AV* but which will not occur at 1 bar. Much activity around the world is evident on both fronts. -RT[d In k / d p ] p + o = AV* -RT[d In K/dp]p+Ogeneral review articles, and data compilation^^.^ in which some 1500 volumes of activation and volumes of reaction of both organic and inorganic reactions are collected. Pressure effects on enzymic reactions,' on displacements from co-ordination com-pound~,~*' and upon isotope effects' are among more specialized articles. The 50th Commemorative Volume of Reviews of Physical Chemistry of Japan is devoted to review articles on Modern Aspects of Physical Chemistry at High Pressure; topics The subject has been thoroughly reviewed recently in two * The units of molar volume throughout this article are cm' mot-'.

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Section: Ph'mentioning

confidence: 86%

Chapter 2. Physical methods. Part (iii) High-pressure chemistry

Isaacs¹

1981

Annu. Rep. Prog. Chem., Sect. B

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“…75 Illustrative examples are portrayed in the [4C2] cycloaddition of hexachlorocyclopentadiene with cis-cycloalkenes 76 (Table 11, and reaction III in Scheme 18) and in the cyclodimerization of 2,3-dimethyl-1,3-butadiene (Table 12). 77 Another example is provided by the [4C2] and [4C4] cyclodimerization of a highly substituted 4,5-bis(methylene)-cyclopentane which proceeds via stepwise mechanism at variance with the route involving the unhindered monomer. 78 In the Diels-Alder reaction of hexachlorocyclopentadiene, q decreases with increasing ring strain.…”

Section: Applicationsmentioning

confidence: 99%

Correlation between pressure and steric interactions in organic reactions

Jenner

2005

Tetrahedron

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“…3 These authors deduced that there is participation of a non-concerted mechanism that has an activation energy several kcal/mol higher in energy than the concerted. 3 …”

Section: Introductionmentioning

confidence: 99%

Computational Investigation of the Competition between the Concerted Diels–Alder Reaction and Formation of Diradicals in Reactions of Acrylonitrile with Nonpolar Dienes

James

Padías

et al. 2013

J. Org. Chem.

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The energetics of the Diels-Alder cycloaddition reactions of several 1,3-dienes with acrylonitrile, and the energetics of formation of diradicals, were investigated with density functional theory (B3LYP and M06-2X) and compared to experimental data. For the reaction of 2,3-dimethyl-1,3-butadiene with acrylonitrile, the concerted reaction is favored over the diradical pathway by 2.5 kcal/mol using B3LYP/6-31G(d); experimentally this reaction gives both cycloadduct and copolymer. The concerted cycloaddition of cyclopentadiene with acrylonitrile is preferred computationally over the stepwise pathway by 5.9 kcal/mol; experimentally, only the Diels-Alder adduct is formed. For the reactions of (E)-1,3-pentadiene and acrylonitrile, both cycloaddition and copolymerization were observed experimentally; these trends were mimicked by the computational results, which showed only a 1.2 kcal/mol preference for the concerted pathway. For the reactions of (Z)-1,3-pentadiene and acrylonitrile, the stepwise pathway is preferred by 3.9 kcal/mol, in agreement with previous experimental findings that only polymerization occurs. M06-2X is known to give more accurate activation and reaction energetics but the energies of diradicals are too high.

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High pressure (4+2) cyclodimerisation of 2,3-dimethyl 1,3-butadiene possible competition between concerted and stepwise mechanisms

Cited by 15 publications

References 13 publications

Chapter 2. Physical methods. Part (iii) High-pressure chemistry

Chapter 2. Physical methods. Part (iii) High-pressure chemistry

Correlation between pressure and steric interactions in organic reactions

Computational Investigation of the Competition between the Concerted Diels–Alder Reaction and Formation of Diradicals in Reactions of Acrylonitrile with Nonpolar Dienes

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