Subject: concerted reaction/ kinetics

From: "Rochus Schmid" <[email-masked]>
Date: Wed, 4 Dec 1996 18:06:25 +0100

Dear netters,

Please help me with the understanding of the following problem:

I can calculate the thermodynamics of a reaction cascade

	AB + C --> A + B + C --> AC + B

The first step is the dissociation of B and the second is the association of C.
The energy barrier (if association and dissociation don't have a barrier, e.g.
a simple morse potential like bond breaking) is equivalent to the dissociation
energy:

	AB --> A + B

right?

Now, if this reaction (or substitution) would be concerted

	BA + C --> [ B-A-C ]# --> B + AC

the barrier is the energy between BA + C and the TS [ B-A-C ].
right?

This is probably (from the point of energy) lower than the two step mechanism.
However, I have the feeling, that the free energy barrier will be different,
since C must "meet" BA, wich should somehow reduce the probability of the
reaction.

OK
Am I right? Or is this stupid?
And is there any possibility after calculating both barriers to estimate the
free energies?
In other words: if the barrier for the concerted reaction is lower, does it
really happen that way?

Thanx in advance for any replies.
I will summarize.

Rochus

-- 

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Rochus Schmid
Technische Universitaet Muenchen	Tel. 	++49 89 2891 3140
Lehrstuhl f. Anorganische Chemie 1	Fax. 	++49 89 2891 3088
Prof. W. A. Herrmann			E-mail:	
Lichtenbergstrasse 4			[email-masked]
85747 Garching
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