Talk:Transition state theory

Section "Applications of TST: enzymatic reactions"

Very interesting section, but it should be integrarted better in the article.

(1) It has several undefined terms.

(2) It should announce somewhere that inhibiting a reaction through mimicking a transition state complex is desirable, either to test theories or prevent reactions (say for medical purposes). As it stands, the idea of inhibition is introduced indirectly, the reader has to be clever to catch it.

178.38.90.162 (talk) 15:14, 4 April 2015 (UTC)

Origin and meaning of symbol ^‡

Can anyone explain WHY the symbol ^‡ is used to denote properties of the transition state? All my textbooks just say that it is so used, but none of them explain the origin and meaning of the symbol. Did it come from Eyring's papers, and did he offer any explanation? Dirac66 (talk) 21:39, 27 October 2016 (UTC)

The assumptions of the quasi-equilibrium seem very odd

Quote:

TST assumes that even when the reactants and products are not in equilibrium with each other, the activated complexes are in quasi-equilibrium with the reactants. As illustrated in Figure 2, at any instant of time, there are a few activated complexes, and some were reactant molecules in the immediate past, which are designated [ABl]‡ (since they are moving from left to right). The remainder of them were product molecules in the immediate past ([ABr]‡). Since the system is in complete equilibrium, the concentrations of [ABl] ‡ and [ABr]‡ are equal, so that each concentration is equal to one-half of the total concentration of activated complexes:[citation needed]

There are two odd aspects here: the last sentence says "since the system is in complete equilibrium" seems to contradict the first sentence. Second, why would the quantities $[AB_l]^\ddagger$ and $[AB_r]^\ddagger$ be equal, unless the activation energies of both forward and reverse reactions are equal (which would imply that starting material and product are the same energy)? Could someone make sense of this? It also isn't well-explained why these facts are significant. Alsosaid1987 (talk) 01:13, 17 December 2018 (UTC)

The argument in this section is indeed a little confused. The second paragraph supposes a true equilibrium between forward and backward reactions, which would mean that the statements you have questioned are true BUT also that there is no net reaction. Then in the third paragraph we change assumptions (!) and suppose that the product is suddenly removed so that the backward reaction stops, but the rate of the forward reaction is unchanged. Then we do have a net reaction whose rate is equal to the forward reaction of the equilibrium in the previous case. It is therefore called a quasi-equilibrium, but is not really an equilibrium at all.

This is however the original reasoning of Eyring, so it does belong in the article. If you want to try to rewrite the argument more clearly to separate the two assumptions, a good reference is J.I.Steinfeld, J.S.Francisco and W.L.Hase, "Chemical Kinetics and Dynamics", 2nd edn, Prentice-Hall 1999, ISBN 0-13-737123-3, p.290-1. Dirac66 (talk) 22:07, 20 January 2019 (UTC)

@Alsosaid1987: I have now dealt with this by just deleting the sentence about complete equilibrium. As you said, it makes no sense, and it contradicts Steinfeld and other sources. Dirac66 (talk) 20:33, 8 October 2020 (UTC)

Thanks for the explanation! Alsosaid1987 (talk) 15:06, 10 October 2020 (UTC)

The article should work with activities instead of concentrations

Also rate equations should be preferably formulated with activities, see https://www.researchgate.net/post/Does-anyone-have-experience-with-the-use-of-activities-instead-of-concentration-in-reaction-rate-equations Biggerj1 (talk) 23:36, 16 December 2020 (UTC)