From owner-chemistry@ccl.net Sun Jul 16 15:44:00 2006
From: "MIQUEL =?iso-8859-1?Q?SOL=C0_I_PUIG?= miquel.sola]_[udg.es" <owner-chemistry**server.ccl.net>
To: CCL
Subject: CCL:G: Can we find the transition state of SN1 reaction by using
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Date: Sun, 16 Jul 2006 18:28:00 +0200 (CEST)
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Sent to CCL by: MIQUEL =?iso-8859-1?Q?SOL=C0_I_PUIG?= [miquel.sola.^.udg.es]

Dear Wenrui and Steve,

We addressed this question some years ago. We found that the energy
profile for the Ch3Cl -> CH3+ + Cl- reaction in the gas phase increases
monotonically, whereas the presence of either uniform electric fields or
solvents changes the energy profile, causing the appearance of a
transition state and the increase of the exothermicity of the process. The
reference is:

M. Solŕ, E. Carbonell, A. Lledós, M. Duran and J. Bertrán.
"Ab initio study of the effect of external perturbations in the
dissociation of CH3Cl"
J. Mol. Struct. (THEOCHEM) 255 (1992) 283-296.

Hope this helps,

Miquel

> Sent to CCL by: Steve Bowlus [chezbowlus!A!goldrush.com]
> It would not surprise me that this type of reaction must be modeled with
>   explicit solvent.  Stabilization of the products relative to the TS is
> attained by solvation of the separated ions, i.e. the physical "flow" of
> solvent between the nascent ions, and the direct (dipolar?) interaction
> of solvent with the ions.  Most physical organic books should have a
> discussion of solvent-separated reaction partners, and most likely SN1
> reactions in particular.
>
> Cheers,
> Steve
>
>
> Wenrui Zheng wenruizheng:gmail.com wrote:
>> Sent to CCL by: "Wenrui  Zheng" [wenruizheng..gmail.com]
>>
>> Dear all,
>>    Recently I have failed to find the transition state of the first step
>> of solvolyses of alkyl halide RX,for example tert-Butylchloride in
>> methanol solvent
>> by using Gaussian03.
>> RX->R+ + X-
>> Following the lengths of C-Cl increasing,the potential energy rises all
>> along,which
>> is the same with the case of in methanol solvent by using PCM model.
>>
>> Now I have some questions:
>> 1. Can we on earth find the transition state of SN1 reaction by using
>> Gaussian03?
>>
>> 2. Is traditional transition state theory adapt to any system for
>> example this one ?
>> If it is true then how can this kind of reaction happen and how can we
>> calculate the
>> reaction rate?
>>
>>   Regards,
>>
>> Wenrui Zheng>
>
>
>