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Date: Tue, 28 Mar 2000 13:01:31 +0800
From: Mao Xiang <xmao $#at#$ iris.sipp.ac.cn>
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To: chemistry -x- at -x- ccl.net
Subject: problem in TS searching
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Hello everyone:
    I met a strange thing in transition state searching in MOPAC. There
are three reactants,  HOCH2CH2NH2, H2O and HCONH2 to complete the
reaction like the following:

                                                                           
NH2
                                                                           
|                                                                     
 HOCH2CH2NH2+H2O+HCONH2--->(+)NH3CH2CH2O(-)+ H2O +HCONH2 --->
(+)NH3CH2CH2O-C-O(-) +H2O
                                                                           
|
                                                                           
H

I use pseudo reaction coordinate technique to find the transtion state
of the first reaction, but when I use PM3 MMOK TS PRECISE to refine it,
I failed. Then I cut off the HCONH2 from the system, I can refine the
first TS I got, because I got one negative frequency. 
    Does anyone have some experients about the problem I met, hope you
can give me some suggestion. Thank in advance.


Regards,
mao
     
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|  Mao Xiang                                                      |
|  Lab of Molecular Regulation for Microbial Secondary Metabolism |
|  Shanghai institute of Plant Physiology, Academia Sinica        |
|  300 Fenglin Road, Shanghai, China, 200032                      |
|  Tel: +86-21-64042090-4791                                      |
|  Fax: +86-21-64042385                                           |
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~