Valence bond representation for the hydrogen atom exchange reaction. [Erratum to document cited in CA119(24):257296t]

It was shown that, when deuterium and ethylene are passed over a nickel catalyst, in addition to the formation of deuterium substituted ethanes, an exchange reaction which may be formulated C 2 H 4 + D 2 ⇄ C 2 H 3 D + HD takes place (Farkas, Farkas and Rideal 1934). Horiuti and Polanyi (1934) pointed out that if the exchange reaction involved atoms, and the addition reaction molecules of hydrogen, the two reactions should differ in their kinetics; this inference is only true under those conditions where the rate-controlling mechanisms involve those species in concentrations in equilibrium with the gas phase. It was found that the two reactions differed at least in respect to their relative energies of activation. If the exchange reaction involves an atomic mechanism, this can be formulated in two different ways (Horiuti and Polanyi 1934), either a primary addition of a deuterium atom, or a primary loss of hydrogen atom may take place, the respective reactions being represented diagrammatically as follows:

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Valence‐bond study of the (H2, D2) exchange reaction mechanism

The Journal of Chemical Physics ◽

10.1063/1.1679302 ◽

1973 ◽

Vol 58 (3) ◽

pp. 1202-1204 ◽

Cited By ~ 10

Author(s):

B. Freihaut ◽

L. M. Raff

Keyword(s):

Reaction Mechanism ◽

Exchange Reaction ◽

Valence Bond

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An Accurate Barrier for the Hydrogen Exchange Reaction from Valence Bond Theory: Is this Theory Coming of Age?

Chemistry - A European Journal ◽

10.1002/chem.200305093 ◽

2003 ◽

Vol 9 (18) ◽

pp. 4540-4547 ◽

Cited By ~ 23

Author(s):

Lingchun Song ◽

Wei Wu ◽

Philippe C. Hiberty ◽

David Danovich ◽

Sason Shaik

Keyword(s):

Exchange Reaction ◽

Hydrogen Exchange ◽

Coming Of Age ◽

Valence Bond ◽

Valence Bond Theory ◽

Bond Theory

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Some Comments on Valence Bond Representations for the Radical Exchange Reaction X•+ R:Y → X:R + Y•

The Journal of Physical Chemistry A ◽

10.1021/jp076864p ◽

2007 ◽

Vol 111 (50) ◽

pp. 13278-13282 ◽

Cited By ~ 3

Author(s):

Richard D. Harcourt ◽

Karin Schaefer ◽

Michelle L. Coote

Keyword(s):

Exchange Reaction ◽

Valence Bond

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Ab initio study of C—H bond breaking in olefins. II. GVB computations on propene ↔ H + cis- or trans-propen-1-yl

Canadian Journal of Chemistry ◽

10.1139/v94-156 ◽

1994 ◽

Vol 72 (5) ◽

pp. 1230-1237 ◽

Cited By ~ 9

Author(s):

George R. De Maré ◽

Earl M. Evleth ◽

Raymond A. Poirier ◽

Guy J. Collin

Keyword(s):

Hydrogen Atom ◽

Minimum Energy ◽

Valence Bond ◽

Basis Set ◽

Bond Rupture ◽

Structural Behaviour ◽

Reaction Coordinates ◽

Dissociation Energies ◽

Linear Behaviour ◽

Dissociation Curves

The Generalized-Valence-Bond-Perfect-Pairing (GVB-PP) method has been used to investigate the structural behaviour, energy, and dipole moment along the reaction coordinates for propene ↔ H + cis- or trans-propen-1-yl. Geometry optimizations were carried out at the GVB(9)/STO-3G level (complete valence shell) for the minimum energy propene structure (complete optimization) and for numerous structures up to r(C—H) = 10 Å (only the elongated C—H distance kept fixed). The dissociation curves are smooth, without a maximum, and yield predicted dissociation energies of propene to H + cis-propen-1-yl and H + trans-propen-1-yl of 555.8 and 554.8 kJ mol−1, respectively. These values are within several percent of those obtained for C—H bond rupture in ethylene using GVB and MCSCF methods with the same basis set. They are obviously too high but they confirm that removal of a hydrogen atom from the CH2 moiety in propene requires about the same energy as removal of a hydrogen atom from ethylene. GVB(7)/6-31G//GVB(9)/STO-3G computations lower the predicted dissociation energies of propene ↔ H + cis-propen-1-yl and H + trans-propen-1-yl to 448.2 and 448.6 kJ mol−1, respectively.The reduced energy concept (ER = (E∞ − Er)/De) is applied to the reaction coordinates. Linear behaviour for In ER versus bond length is observed at long bond distances. At r(C—H) = 3 Å, the values of the slopes, d(ln ER)/dr(C—H), which are related to the effective Morse constant B are −3.73 and −3.74 (GVB(9)/STO-3G) and −2.75 and −2.81 (GVB(7)/6-31 G//GVB(9)/STO-3G) for the H + cis- and H + tras-propen-1-yl reaction coordinates, respectively.

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