Theoretical secondary kinetic isotope effects and the interpretation of transition state geometries. 1. The Cope rearrangement

Houk, K. N.; Gustafson, Susan M.; Black, Kersey A.

doi:10.1021/ja00048a032

Cited by 116 publications

(67 citation statements)

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“…[31] We use 1.0 (0.0) and 0.0 (1.0) as n R , and n P for the C À X (Nu À C) bond, respectively, and adopt a = 0.6 based on the suggestion in the literature. [31][32][33] The results are listed in Table 1.…”

Section: Resultsmentioning

confidence: 99%

G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon

Ren

Yamataka

2006

Chemistry A European J

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As a continuing theoretical study on the alpha-effect in the S(N)2 reactions at saturated carbon centers, 28 gas-phase reactions have been examined computationally by using the high-level G2(+) method. The reactions include: Nu(-)+CH(3)X-->CH(3)Nu+X(-) (X=F and Cl; Nu(-)=HO(-), HS(-), CH(3)O(-), Cl(-), Br(-), HOO(-), HSO(-), FO(-), ClO(-), BrO(-), NH(2)O(-), and HC(==O)OO(-)). It was found that all alpha-nucleophiles examined exhibit downward deviations from the correlation line between the overall barriers and proton affinities for normal nucleophiles, indicating the existence of the alpha-effect in the gas phase. The transition states (TS) for the alpha-nucleophiles are characterized by less advanced C--X bond cleavages than the normal nucleophiles, leading to smaller deformation energies and overall barriers. The size of the alpha-effect is related to the electron density on the alpha-atom, and increases when the position of alpha-atom is changed from left to right and from bottom to top in the periodic table. The reaction with CH(3)F exhibits a larger alpha-effect than that with CH(3)Cl, which can be explained by a later TS and a more positively charged methyl group at the TS for CH(3)F, [NuCH(3)F](- not equal). Thus, a higher electron density on the alpha-atom and a more positive methyl moiety at the TS result in a larger alpha-effect.

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Section: Resultsmentioning

confidence: 99%

G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon

Ren

Yamataka

2006

Chemistry A European J

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“…(2)]. The C 2h -symmetric structure is a transition structure at B3LYPS, but an intermediate at MP2/S, [53] while its associated transition state is dissymmetric with CÀC bond-breaking/forming lengths of 1.761 and 1.814 , indicating an asynchronous diradicaloid pathway; no open shell singlet states were located. However, the difference in activation energy between MP2/L//B3LYPS and MP2/L//MP2/S is only 1.0 kcal mol À1 and at SCS-MP2/L even smaller (0.8 kcal mol…”

Section: Methodsmentioning

confidence: 99%

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Goumans

Ehlers

Lammertsma

et al. 2004

Chemistry A European J

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A new quantum mechanical scheme to calculate electronic correlation energies, spin-component-scaled MP2, was tested as a tool to predict reaction energies and barriers in computational organic chemistry. Three common pericyclic reactions with known unsatisfactory MP2 descriptions were reinvestigated with the modified MP2 approach, in which the parallel and anti-parallel spin components of the correlation energy are scaled separately. The SCS-MP2 calculated reaction and activation energies of nine Diels-Alder reactions, four [3,3] sigmatropic rearrangements, and ten electrocyclization reactions are compared to those of the MP2, B3 LYP, QCISD(T), and G3 methods. For each, the SCS-MP2 results are in excellent agreement with the experimental data and compare far more favorably to G3 than both MP2 and B3 LYP. Careful evaluation of the effect of the size of the atomic orbital (AO) basis set shows that the larger expansions improve the agreement with experiment for the SCS-MP2 method, while they get worse for both MP2 and B3 LYP.

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“…The study of KIEs in such reactions is of particular interest. There have been numerous experimental [1][2][3][4][5][6][7][8][9][10][11][12][13][14]22,23 and theoretical [15][16][17][18][19][20][21][24][25][26][27][28][29][30][31][32][33][34] studies performed on proton transfer in systems of chemical and biochemical interest.…”

Section: Introductionmentioning

confidence: 99%

Primary and Solvent Kinetic Isotope Effects in the Water-Assisted Tautomerization of Formamidine: An ab Initio Direct Dynamics Study

Bell

Truong

1997

J. Phys. Chem. A

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We present an ab initio direct dynamics study of the primary and solvent kinetic isotopes effects (KIEs) for the water-assisted tautomerization in the formamidine-water complex. These calculations are based on a variational transition state theory plus multidimensional semiclassical tunneling corrections with potential energy information calculated at the MP2 level of theory using the 6-31G(d,p) basis set. We found that both the primary and solvent KIEs are large at low temperatures and are due not only to tunneling but also to quantum effects in vibrational motions. The primary KIEs were larger than the solvent KIEs. This results from differences due to the effect of deuteration on vibrational modes. Bending modes show significant inverse KIEs, while those of the reactive OH and NH vibrations show both inverse and normal effects. Such effects can be explained by examining changes in the zero-point energies of these modes. The adherence of the HH/HD/DD rates to the rule of the geometric mean is also examined.

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Theoretical secondary kinetic isotope effects and the interpretation of transition state geometries. 1. The Cope rearrangement

Cited by 116 publications

References 0 publications

G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon

G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Primary and Solvent Kinetic Isotope Effects in the Water-Assisted Tautomerization of Formamidine: An ab Initio Direct Dynamics Study

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Theoretical secondary kinetic isotope effects and the interpretation of transition state geometries. 1. The Cope rearrangement

Cited by 116 publications

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G2(+) Investigation on the α‐Effect in the SN2 Reactions at Saturated Carbon

G2(+) Investigation on the α‐Effect in the SN2 Reactions at Saturated Carbon

Improved Reaction and Activation Energies of [4+2] Cycloadditions, [3,3] Sigmatropic Rearrangements and Electrocyclizations with the Spin‐Component‐Scaled MP2 Method

Primary and Solvent Kinetic Isotope Effects in the Water-Assisted Tautomerization of Formamidine: An ab Initio Direct Dynamics Study

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G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon

G2(+) Investigation on the α‐Effect in the S_N2 Reactions at Saturated Carbon