[CHM 331] Capsule question

[Andrew J. Pounds]

On 04/24/2017 08:05 PM, Kathryn Elizabeth Morris wrote:
>
> On capsule 9, I am still trying to figure it out. On the example 
> graph, it shows two wells, the a dot at the bottom of each of them. 
> What energies are these associated with? I am confused on what they mean.
>
>
> Thanks,
>
> Katie Morris
>

Look below the graph -- there are some pictures of a molecule undergoing 
and SN2 reaction.   Going across the page from left to right you have


1.   A neutral CH3Cl molecule and a Chlorine ion

2.   A system in which the reaction is starting with the Chlorine ion 
attacking from the bottom

3.   A system representing the "transition structure"

4.   A system in which re reaction is completing with the other Chlorine 
atom about to be ejected from the top

5.   A neutral CH3Cl molecule and a Chlorine ion


Numbers 4 and 5 are energetically identical 2 and 1 based on symmetry.  
So you really only have to a few calculations to determine the three 
energies.


1. You need to add the energy of the neutral molecule to that of the 
chlorine ion

2. You need to find the energy of the "van der Walls complex"  (this 
requires scanning in redundant coordinates)

3. You need to find the energy of the transition state  (can be done as 
part of previous calculation)


Those three numbers represent the energies of the horizontal lines on 
the graph.  You should be able to calculate the changes in energy 
accordingly.




-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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