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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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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Transition state and free energy
We have products $\ce{A + B}$ combining to form $\ce{C + D}$ through the transition state $\ce{X}$.
Are all reactions at least virtually reversible? Is the difference between a reversible reaction ...
user1160
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Why are the total energies of transition states so commonly corrected for zero-point vibrational energy?
So often I see total energies of transition states corrected for zero-point vibrational energy which always confuses me. Zero point energy is the lowest energy that a ground state minimum energy ...
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Finding chair and boat transition states during ring-forming reactions
Reactions that form 6 membered rings most commonly go via either boat or chair transition states but the products themselves do not necessarily adopt the same conformation as the TS.
I'm attempting ...
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Units of rate constant (cycles per second vs radians per second) in Eyring equation
In the Eyring equation (EE),
$$k = \frac{k_\mathrm B T}{h} \exp\left(\frac{-\Delta G_{\mathrm f}}{RT}\right),$$
the units of $k$ are $\mathrm{s^{-1}}$. However, in general rate constants are usually ...
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Transition state optimisation on the surface of periclase
I want to model a reaction catalysed by periclase ($\ce{MgO}$) using DFT.
I have a good guess on the transition state (TS) of the reaction that goes in gas phase/solvent (produced using MOPAC).
The ...
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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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When are transition state's energy barrier "reasonable" at a certain temperature?
Every computational chemist who does a little bit of mechanistic studies has asked himself this question. When you obtain your first transition state and look at the activation barrier needed to ...
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Transition state - multidimensional surfaces
I've been reading an explanation about transition states in Smith's Organic Synthesis:
A transition state is an energy maximum along the reaction coordinate. However, a chemical
reaction where ...
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References for Transition State Theory and Quantum Transtion State Theory
Having asked recently this, I started to look for good references and notes on Transition State Theory and, also, modern versions of it including things like tunneling (which isn't taken into account ...
user28429
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Unix/MobaXterm Project Assistence (Knowing the Error in my Output File)
I'm a student and I recieved a project in which I am supposed to simulate a transition state in an $\mathrm{S_N2}$ reaction.
The first instruction in this project is to use a benchmark reaction in ...
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Calculation of rate constant for bimolecular reaction from Gaussian DFT calculations
I am working with a bimolecular reaction for which I have computed the energy profile. I have output files for TS and reactants which I intend to use for rate constant calculations. From TST we have:
...
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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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Why only molecules with three or more atoms undergo unimolecular reaction?
Only molecules with three or more atoms undergo unimolecular reactions. A diatomic molecule cannot dissociate in this way because it has a single mode of vibrational freedom. If this mode is excited ...
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Why some reaction have no transition state?
All stationary point are local minimum, if any parameters changed the energy should be increase. There is no way for a stationary point that energy go straight down to reach another.
I was told that ...
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