Subject: How can one calculate reaction rate constant?

From: "Alexei Khalizov" <[email-masked]>
Date: Mon, 14 Feb 2000 18:51:16 -0500

<color><param>0100,0100,0100</param><FontFamily><param>Times New Roman</param><bigger>Dear CCLers,

I would like to calculate rate constant k for bimolecular reaction 
A + B -> AB. I have found transition state and proved that it 
really connects reagents and products (G98w, GAMESS). 
According to RRKM the simplest expression for calculation of 
rate constant k is

k = (kB*T/h)(Q’’/Qa*Qb) exp(-Eo/RT),

where kB is Boltzmann’s constant; Q’’, Qa and Qb are partition 
functions for TS and reagents A and B; Eo – difference in zero 
point energies of TS and reagents. 

Question: what units and what measure does this rate constant k 
have? Simple evaluation gives units of [s-1], but being a 
bimolecular it is expected to have units of  [M-1s-1], [cm3 
molecules-1 s-1] or such. How can we account for this?

Sincerely,

Alexei Khalizov,

</color>Balakrishnan Viswanathan

-------------------------
Dr. Alexei Khalizov
Departments of Chemistry
McGill University,
801 Sherbrooke St. W.,
Montreal, Quebec, CANADA,
H3A 2K6