Subject: HELP: kinetics and computers

From: "Dr. Jose Santiago Duca (h)" <[email-masked]>
Date: Wed, 04 Dec 1996 19:02:03 -0200

Dear CCL'ers,

I got a problem (maybe completely out of theme, if so my sincere
apologies) with the following experimental system because I cannot find
the corresponding global kinetic equation, 

     k1
I0  ---->  I1 + X

          ka
I1 + Nu  ---->  I2

          kT
I2 + R1  ---->  P1 + I0

     k2
I3  ---->  I4 + X

          ka
I4 + Nu  ---->  I5

          kT
I5 + R2  ---->  P2 + I3

           K12
I0 + R2  <====>  R1 + I3  (this is a fast equilibrium, K12=k12/k21)

          kT
I5 + R1  ---->  P2 + I0

          kT
I2 + R2  ---->  P1 + I3

This system correspond to a SRN1 competition reaction of two substrates
by a nucleophile, and the problem with it is that the limitant steps are
those of k1 and k2 constants, which take place LATER than the fast
equilibrium reaction, so P1 and P2 are linked...
I know that all intermediates (I0, ...I5) can be treated as in
stationary state, but...

what I want to know is the expressions of dP1/dt and dP2/dt (much better
(dP1/dt)/(dP2/dt) as the relative rates) as functions of the initial
quantities of R1, R2 and maybe of P1 and P2 since **the only thing** I
can messure is the final yield of the products P1 and P2!!

I have been trying to deal with this problem with no success because I
am not an expert on kinetics and I haven't found any useful example on
kinetic books, so I am asking you for help.
Is there any program that can manage systems like that or simulate
kinetic systems in order to find the kinetic equation, or does anybody
know about a reference of similar systems or something?
Do there exist any people who can help me or give me some useful advice
about how to solve the system?

Any comments are welcome, 

Thank you in advance.

Jose

-- 
Dr. Jose Santiago Duca (h)

e-mail: [email-masked]
URL: http://zeus.uncor.edu/jsd/jsd.htm

---

From: Kenneth Geisshirt <[email-masked]>
Date: Wed, 4 Dec 1996 19:57:22 -0700 (MST)

Dear Dr. Duca,

If you need a numerical simulation of any kinetic scheme, I might have a
program that can help you. But then you need the numerical values of the
rate constants and so on. The program can be downloaded from my home page
at address: http://virgil.ruc.dk/~kneth/software.html - the program is
called KCI. The manual is not yet completed, but some parts can the read
on-line at the same address.

Best wishes
  Kenneth

+-----------------------------------------------------------------+
| Kenneth Geisshirt                                 Ph.D.-student |
| Department of Life Sciences and Chemistry,  Roskilde University |
| Currently at: University of Colorado at Boulder                 |
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| [email-masked]                 http://virgil.ruc.dk/~kneth/ |
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