Subject: Help with transition states

From: "Mus Musculus" <[email-masked]>
Date: Thu, 31 Jan 2002 14:28:09 +0100

Hello!
Excuse me if my question seems too basic for this forum, but I'm a newcomer 
in this field and I'm feeling quite lost.

I'm trying to locate the transition state of a electrocyclic opening of a 
cyclopropane ring to yield an allyl cation. Is there a kind of established 
methodology to follow in this cases (a way of making an "educated guess" for 
the geometry of the TS)?
Do you think the outcoming of the reaction being two ions requires a special 
treatment?
I would gladly receive any piece of information about the location of 
transition states either in general or in electrocyclic reactions.

Thank you in advance.

Viv.

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---

From: David Gallagher <[email-masked]>
Date: Thu, 31 Jan 2002 16:20:19 -0800

Minimizing the gradient of a starting guess is one approach but there are 
other methods that may or may not work better.

You can download a "Guide to Transition State Modeling" at 
http://www.cachesoftware.com/solutions/index.shtml  or
http://www.cachesoftware.com/pdfs/CACheGuideTransitionStateModel.pdf

The default MOPAC method (singlet) will force the electrons to remain 
paired, but you can switch to UHF to allow for radicals.

David Gallagher, Fujitsu

At 02:28 PM 1/31/2002 +0100, Mus Musculus wrote:
>Hello!
>Excuse me if my question seems too basic for this forum, but I'm a 
>newcomer in this field and I'm feeling quite lost.
>
>methodology to follow in this cases (a way of making an "educated guess" 
>for the geometry of the TS)?
>Do you think the outcoming of the reaction being two ions requires a 
>special treatment?
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