Dear Dang T. Nguyen

I think that we have to start analyzing and check the structure with XRD, NMR, IR, TGA and chromatography techniques for each reactant and product.

Then we have to look at the nearest reaction by searching about the differences that happened with reactants. by this we should be much nearest to the reaction that we looking for.

I hope my answer will be helpful

Best regard

Dear Nguyen,

Many reactions will take place in barrier less reactions in this case true transition state is not located. Some reactions will takes place with some amount of barrier in that case we should try to guess true transition states for the concerned reactions. we can guess the transition state structure by using two approaches QST2 and QST3 methods. Another way is to optimize the guess structure alone by using the command opt=(ts, calcall, noeigen). Some of the DFT methods produce very good results in chemical reactions are namely M06-2x, wB97XD and MPWB1K methods.

Thanks in advance.

identify the reaction mode and maximize energy along this mode while minimizing energy in all other directions. One reason why transition state optimization is more difficult than the search for a minimum is that a successful search should start off in a region where the reaction coordinate already has a negative curvature. In other words, search for a transition state should start near the transition state.

Dear Dang T Nyugen,

If you don't mind, you can mail me([email protected]) in details on this regard. If I can be of any help for your problems, I will try to locate TS and look into it.

Thanks.

Lily

Dear,

Every chemical reaction will surely proceed via transition state. If you have well known structures of reactant and product then we have to notice structural change. Using reactant and Product structure, we can easily obtain TS structure by using any quantum calculation software .

Dear Dang T. Nguyen thank you for asking this interesting technical question. According to the transition state theory, all chemical reactions pass through an unstable structure which is termed the transition state. The transition state is located between the chemical structures of the substrate and the products. For some general information about this please have a look at the Wikipedia entry on "Transition state theory" at

https://en.wikipedia.org/wiki/Transition_state_theory#Enzymatic_reactions

Also please have a look at the following useful link:

Transition State Theory

https://courses.lumenlearning.com/introchem/chapter/transition-state-theory/

Dear Frank T. Edelmanm and Nand Kishor Gour,

I am not sure that : "Transition state theory" is always right and it could be applied for any chemical reaction. For example: NaOH + HCl or Redox reaction,....These kinds of chemical reaction occur very fast, whether could it exist really a transition state structure or not? Should we propose a limit range of reaction rate which it could exist a transition state structure to look for it through the modeling job using computational chemistry. I mean so.

Best regards.

Dear Lily Makroni,

Thanks for your great suggestion. I will email to you in the near future to get some support for the calculational job.

Best regards.

Dear Bakr Aldoori,

Thanks for interesting response. But I do not understand your mean. How do you guess when you have chromatography and spectra of reactants and products?

Best regards.

Dear Gunasekaran Manonmani and T. H. Al-Noor,

Thanks for your valuable share. However, here my mean like as I have mentioned in the above response to Frank T. Edelmanm and Nand Kishor Gour. I do not ask how to look for a transition state structure by the calculational job.

Best regards.

Interested

Dear Prof. Dr. Nada Farhan Kadhim.

Thanks for your valuable contribution in the discussion.

Best regards.

Hi,

Some reactions involving radicals or ions are experimentally observed to be non-barrier, which occurs when the potential of the product crosses that of the reactant at its minimum (i.e., between the "normal" and "reverse" regions). Reactions then take place spontaneously. For the description of reaction mechanisms, theoretical studies are now at the heart of this effort (computational chemistry). They bring to the experimental data the framework of an atomic and molecular description of the structures. They even guide the experiments in new directions.

Please see the links bellow:

https://chemistry.stackexchange.com/questions/98424/why-some-reaction-have-no-transition-state

https://pubs.acs.org/doi/10.1021/ar900013p

https://pubs.acs.org/doi/10.1021/jp070736j

With my best regards

There are so many different types of chemical reactions. What is the chemical reaction you are referring to?

Dear Prof. Dr. Vadim S. Gorshkov, Prof. Dr. Doufnoune RACHIDA Rachida, Dr. Kolita Weerasekera,

Thanks for your valuable contribution in the discussion.

Best regards.

HI Dear Dang T. Nguyen . Transition state theory (TST) provides a simple and useful way to understand and determine the rate coefficients of chemical reactions. It was first proposed by Eyring and Evans-Polanyi in 1935. So transition state is a proposed state not real or actual state . All reactions have theoretically transition states. See the following useful link: https://www.sciencedirect.com/topics/chemistry/transition-state-theory

Kindly see also the following very good link: https://www.sciencedirect.com/topics/chemistry/transition-state-structure

See also the following very good link: https://www.nature.com/articles/s41597-020-0460-4

Dear Dang T. Nguyen

All questions can be solved in the software product QCC Front End. As they say, you can design, calculate all possible variants of reactions with different isomers. If there are specific types of reactions, write, I'll see what I can offer.

Regards, Sergey