Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 934-942
Author(s):  
J Peter Guthrie
Keyword(s):  
Carbon Dioxide ◽  
Free Energy ◽  
Equilibrium Constants ◽  
Marcus Theory ◽  
Energy Of Activation ◽  
Free Energies ◽  
Orbital Theory ◽  
Activation Free Energy ◽  
Free Energy Of Activation ◽  
Rms Error

Rate constants for hydration of carbon dioxide and ketene can be calculated by applying No Barrier Theory, which needs only equilibrium constants and distortion energies, the latter calculated using molecular orbital theory. The calculated free energies of activation are in satisfactory agreement with experiment: the rms error in free energy of activation is 2.38 kcal/mol. These compounds can also be described using Marcus Theory or Multidimensional Marcus Theory using the transferable intrinsic barrier appropriate to simple carbonyl compounds; in this case the rms error in free energy of activation is 2.19 kcal/mol. The two methods agree on preferred mechanistic path except for uncatalyzed hydration of ketene where Multidimensional Marcus Theory leads to a lower activation free energy for addition to the C=O, while No Barrier Theory leads to a lower free energy of activation for addition to the C=CH2. A rate constant for hydroxide ion catalyzed hydration of ketene can be calculated and is in accord with preliminary experimental results.Key words: ketene, carbon dioxide, hydration, Marcus Theory, No Barrier Theory.

Elimination reactions – Calculation of rate constants from equilibrium constants and distortion energies by means of no barrier theory

2005 ◽  
Vol 83 (9) ◽  
pp. 1654-1666 ◽  
Author(s):  
J Peter Guthrie ◽  
Leonardo Leandro ◽  
Vladimir Pitchko
Keyword(s):  
Free Energy ◽  
Alkyl Halide ◽  
Equilibrium Constants ◽  
Free Energy Of Activation ◽  
Carbon Carbon Bond ◽  
Alkyl Bromides ◽  
Encounter Complex ◽  
Leaving Group ◽  
Reaction Proceeds ◽  
Rms Error

No barrier theory has been applied to the E2 reactions of five alkyl bromides with ethanolic ethoxide. The model used for these reactions is that the reaction proceeds from the encounter complex of base and alkyl halide to the product encounter complex of halide ion and alkene (and alcohol), and requires five simple processes, which combine to give the concerted elimination: transfer of a proton from carbon to base; a change in geometry at the carbon which loses a proton from sp3 to sp2; breaking the C-leaving group bond; a change in geometry at the carbon which loses the leaving group from sp3 to sp2; and a change in the length of the carbon–carbon bond. The free energy of activation can be calculated with an rms error of 2.58 kcal mol–1 (1 cal = 4.184 J).Key words: Elimination, no barrier theory, rate constant, equilibrium constant.

Viscosity of Dimethyl Sulfoxide + 1,4 Dimethylbenzene System

2008 ◽  
Vol 59 (1) ◽  
pp. 45-48
Author(s):  
Oana Ciocirlan ◽  
Olga Iulian
Keyword(s):  
Free Energy ◽  
Dimethyl Sulfoxide ◽  
Atmospheric Pressure ◽  
Entire Range ◽  
Polynomial Equation ◽  
Energy Of Activation ◽  
Excess Gibbs Free Energy ◽  
Experimental Measurements ◽  
Gibbs Energy Of Activation ◽  
Free Energy Of Activation

This paper reports the viscosities measurements for the binary system dimethyl sulfoxide + 1,4-dimethylbenzene over the entire range of mole fraction at 298.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The experimental viscosities were correlated with the equations of Grunberg-Nissan, Katti-Chaudhri, Hind, Soliman and McAllister; the adjustable binary parameters have been obtained. The excess Gibbs energy of activation of viscous flow (G*E) has been calculated from the experimental measurements and the results were fitted to Redlich-Kister polynomial equation. The obtained negative excess Gibbs free energy of activation and negative Grunberg-Nissan interaction parameter are discussed in structural and interactional terms.

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

scholarly journals Rationalisation of the activities of phenolic (vitamin E-type) antioxidants

2003 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Christopher J. Rhodes ◽  
Thuy T. Tran ◽  
Philip Denton ◽  
Harry Morris
Keyword(s):  
Free Energy ◽  
Vitamin E ◽  
Gibbs Free Energy ◽  
State Theory ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Gibbs Free Energy Change ◽  
Linear Free Energy ◽  
Free Energy Of Activation ◽  
Enthalpy And Entropy

Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

Thermodynamic studies in solution. Part IV. Solvent effect on the solvolysis of tert-butyl chloride. A new treatment of the experimental data

1979 ◽  
Vol 57 (5) ◽  
pp. 500-502 ◽  
Author(s):  
Joaquim Jose Moura Ramos ◽  
Jacques Reisse ◽  
M. H. Abraham
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Free Energies ◽  
Butyl Chloride ◽  
Activation Free Energy ◽  
Tert Butyl ◽  
New Treatment ◽  
The One ◽  
Activated Complex ◽  
Tert Butyl Chloride

A new treatment of the solvent effect on the solvolysis of tert-butyl chloride is proposed. This treatment is based on activation free energy measurements and on transfer free energy measurements of the reactant (R) on the one hand and of a model (M) of the activated complex (AC) on the other hand. Solute–solvent interaction free energies for the reactant, the activated complex and the model compound are estimated. This estimation involves the calculation of the free energy of cavity formation of these various solutes (R, AC, and M) in all the solvents. These cavity terms, which are a function of the cohesive properties of the solvent and of the surface of the cavity do not reflect the electronic structure of the solute whereas the interaction free energy term does. The method we propose can be described as a new 'experimental' approach for the study of the charge separation in an activated complex.

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