The kinetic compensation effect (KCE) is the subject of extended debates concerning its meaning and the reality of the effect itself. For a good discussion you can read the Wikipedia article under the title of KCE where a preponderance of evidence suggest it to be an artifact arising from the errors incurred in the relation linking DeltaH and Delta S. There is an interesting excercise described in a kinetics book and cited in the Wikipedia article that creates the KCE using the phone numbers of some faculty members of some (any) university,i.e. it's just statistical artifact along with the isokinetic temperature, not a real physical entity. No one seems to have a better explanantion.

Hi,

Cornish-Bowden has written an interesting review on the subject. Please see the attachment for details.

Yes, it is true, KCE can be deduced from EES (ΔH = TisoΔS + ΔHiso). Very interesting papers in the field of KCE.

KCE is merely a "fudge factor" resultung from the nionsense of having applied the Arrhenius Equation to transport-controlled processes; "garbage in, garbage out". Late Prof. Garn was exposing this nonsense for decades, but in vain, to the deaf ears. An alternative, realistic approach is proposed in

Czarnecki J, Sestak J.,  Practical thermogravimetry. J Therm Anal

Calorim. 2000;60:759–78.

I completely agree with Theodore Mill. KCE is often called the enthalpy-entropy compensation

https://en.wikipedia.org/wiki/Enthalpy%E2%80%93entropy_compensation

The lower activation energy requires a formation of  highly organized system (high entropy activation). The correlation is qualitative and commonly can't be used practically. 

Dear Jerry. KCE is usually applicable for the elementary bimolecular reactions and it has nothing to do with the transport-controlled processes. Your language is rather rude for a scientific discussion. You seem to advertise your paper. I read it, it's not directly related to KCE

Dear Yuri

iConnection between KCE and EES can be easily demonstrated by activation functions. This effect definitely exist, but experimental determination of isokinetic temperature is the fundamental problem. In the given link to Wikipedia it is designated as β for all cases. Meanwhile, it can be shown that according to various sources there are huge differences for the KCE, eg. for calcite as reported by L’vov Tiso = 1200 K, while according to the Annex it is lower Tiso = 821 K (Fig.5, a1 vs a2 results from Eqs(15) or (16) in the Annex).

Our studies show that the temperature variation depends on how to implement the process: isothermal or dynamic conditions, different preparation and sample mass.

I think that this problem discourages the acceptance of KCE / EES.

Dear Andrzej, As I wrote the KCE is usually applicable for the elementary bimolecular reactions. The lower activation energy requires a formation of highly organized system (high entropy activation). In general this is  a qualitative correlation between activation parameters. The rate constants are exponentially dependent on activation parameters. Therefore, the predicted value of the rate constant of unknown reaction may very withing 2-3 orders of magnitude. KCE IS NOT applicable for the reactions with a complex reaction mechanism. For all these reasons I don't understand the usefulness of KCE concept. KCE does exist but and I agree with you that numerous factors "discourage the acceptance of KCE / EES"

Dear Yurii, 

My fault, I was ignorant that, as you said, "KCE is usually applicable for the elementary bimolecular reactions". I have always known KCE as an element of thermoanalytical kinetics, where IT IS used for diffusion-controlled macro-processes. Late Prof. Paul D. Garn at every thermoanalytical conference was demonstrating clearly KCE in thermal analysis to be a nonsense, and never, not a single participant opposed him.  I was puzzled, and asked a thermoanalytical doyen: "Garn keeps telling, in effect,  that we are idiots; should not there be a debate, rather than the silence?"  That prominent Professor said: "Jerry, be practical. I have to use the tools I have. Do you want me to stop working because the models that we are using are imperfect?"

In my opinion imperfect theories is one thing, and wrong models is another. The Flogiston theory was not approximating the truth, it was 100% wrong. According to the current therrmoanalytical models the "apparent/formal" activation energy of thermal decomposition of calcium carbonate can change by the factor of 10exp69 when the sample size changes.  10exp69 - more than the number of atoms in our Galaxy!  Yes, with aging I am losing patience for those who say that such numbers are correct because the computer has calculated them. Hence my rudeness.

The  inherent fault and flaw of thermoanalytical kinetics was  having applied the Arrhenius equation to macro-processes in solids - the rest, those tens of its out-of-this-world theories, is the product. Our article proposes abandoning the micro-viewpoint and switching to the realistic macro one. Since it differs radically from the mainstream, it came and went unnoticed, so I did use this small opportunity to let it be know.  If this is advertising, I have to live with this shame.   By the way, our article is related to KCE, indirectly, since KCE is a part of the kinetic models we are criticizing.

I appreciate your criticism, it inspired me.

Dear Yurii,

Continuing the discussion I think there is no clear boundary between the elementary and the complex reactions/processes. I enclose a cumulative figure, at which the results from Fuel (72,1993,1537-1539) are published and also additional. All studies concern coal pyrolysis and all studies are performed in thermogravimetric conditions, so samples were finely divided. But there were various types of coal, various equations and even variable temperature ranges and different laboratories. Conclusion: it is the same pyrolysis process, derogations from linear relation suggest the entropy variation of the test samples, for example changing the reaction mechanism for the lump samples. The A parameter is changing, and simultaneously the activation energy E is also changing in the same direction.

I am grateful for your presented opinion.

Andrzej

KCE concept is based on Eyring equation, which is applicable for elementary reaction.

The definition of elementary reaction from IUPAC Golden Book:

elementary reaction

A reaction for which no reaction intermediates have been detected or need to be postulated in order to describe the chemical reaction on a molecular scale. An elementary reaction is assumed to occur in a single step and to pass through a single transition state.

For the complex reaction KCE does not have any "physical / chemical meaning"

Without knowing the reaction mechanism KCE can't be rationalized. 

Dear Yurii, thank you very much for consultations and an excellent source of knowledge in this field.

Andrzej