Questions tagged [transition-state-theory]
Questions related to explanations of the reaction rates of elementary chemical reactions. The theory assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated transition state complexes.
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What is the Best Transition State Search Method
I want to find transition states (TS) on the potential energy surface (PES) of small/medium reactions with sinle-ended methods. For example the reaction network from here. I've been looking at ...
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Is the minimum energy pathway a geodesic in the potential energy surface?
I just finished NEB-TS calculation using Orca 4.2.1. One of the output file is the minimum energy pathway (MEP) data. Am I correct to interpret the MEP as the geodesic (path of minimum length) on the ...
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Ambimodal transition states in some organic reaction pathways
In many computational studies, mechanisms appear to have so-called ambimodal transition states, i.e. a transition state which can lead to multiple products, in conflict to the common undergraduate ...
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Why does alpha-carbon substituents increase the rate of E2 reactions?
The reason for more reactivity of more substituted alkyl halides for E2 Reaction is said to be due to the more stability of its more substituted alkene character having transition state but here (...
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Gibbs free energy of transition and activation energy
Let's consider a reaction A (reactant) -> B(product) and activated complex is denoted by C.
This graph ( potential energy vs reaction coordinate ) tells us that reactant need some amount of ...
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Can there be two transition states (first order saddle point) connecting the same pair of minimas on a potential energy surface?
This is a purely hypothetical question. Consider a pair of local minimas A and B on a multi dimensional potential energy surface. Can there be two first saddle points (IE two different configurations) ...
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NMR and dienes to isolate certain isotopes?
I am looking to achieve isotope separation using transition states.
In the rxn of dienes with halogens, based on the temperature, the dienes can create a thermodynamic product or a kinetic product. ...
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Can AMBER as low-layer be used to model reaction mechanisms using ONIOM? If yes, do you need to parameterize the intermediates and Transition states?
I'm debating moving from (M06-2X:PM7:UFF) to (M06-2X:PM7:AMBER) for modelling a reaction mechanism in an enzyme. I've already examined the errors introduced by my partitioning and whether they cancel ...
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Why is the transition state the highest energy point? [closed]
If partial bonds form during transition state, it means some energy is released, so how can it have the highest energy? Shouldn't the point before transition state be highest energy? (the point where ...
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How to estimate the temperature needed to overcome an activation energy barrier?
Trying to elucidate a reaction pathway, I calculated the energies for different transition states possible for that reaction (computational chem. DFT). I found activation free energies ranging from 29 ...
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Can rate constant depend upon the concentration of reactants (or other species involved in the reaction)?
Transition state theory tells us that the rate constant of an elementary step is $$k_\mathrm{r} = \frac{\kappa k_\mathrm{B}T}{h}\exp\left\{\frac{- \Delta G^\ddagger}{RT}\right\},$$
where $\Delta G^\...
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Is standard change in activation Gibbs free energy indepedent of pressure?
For a chemical reaction the activation volume is defined as:
$$Δ^{\ddagger}V={V^\ddagger}-V$$
where both $V^\ddagger$ and $V$ refer to standard states (I have omitted the symbol for simplicity). One ...
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What is the reasoning behind the assumptions of Transition State Theory?
We were told in a first year introductory Thermodynamics and Kinetics lecture, and also from Wikipedia, that there are 3 main assumptions for the derivations used in Transition State Theory, but I'm ...
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Understanding transition state theory
Let's say we have standard chemical reaction given by
$$A-B + C \leftrightharpoons [A\cdot\cdot B\cdot\cdot C]^{\dagger} \rightarrow A +B-C$$
I want to estimate the pre-exponential factor of this ...
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Entropy of Activation and Temperature Dependence
I am trying to understand the extrapolation of enthalpy $\Delta H^{\ddagger}$ and entropy of activation $\Delta S^{\ddagger}$ from the Eyring equation. It's typically cast as:
$$\ln\left(\frac{k}{T}\...
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