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Re^3: solvent effect

Thomas Pijper
thomaspijper@hotmail.com


Dear David,

A larger difference might be reasonable to expect. However, it is important to realize that PCM solvation has its limitations. It simulates the interaction of a solute with a continuum through dielectric theory. As such, it cannot account for hydrogen bonding, the protic/aprotic nature of the solvent, multipole interactions, etc.

Also, the 1,3-dicarbonyl structure you've used is somewhat acidic. That might skew the results.


Kind regards,
Thom


On Fri Feb 14 '14 3:20am, David G. wrote
----------------------------------------
>>Dear Thom

>I have calculated the solvent effect of a 1,3-dicarbonyl like system (diketo) which was experimentally shown that is predominated case in solvents of high polarity. In the following you can see the free energy values in gaseous state and different solvents. Also the input/output files were attached.  

>free energy of diketo (gaseous) : -345.80484232 - 231.220/2625.5 = -345.716775 H
>free energy of diketo (water): -345.81631349 H
>free energy of diketo (benzene): -345.8099058 H

>couldn't a larger difference between the free energies be reasonable ?
>
>
>
>
>
>On Thu Feb 13 '14 11:21am, Thomas Pijper wrote
>----------------------------------------------
>>Dear David,

>>Are you sure that HF is a good 'benchmark' to investigate solvation effects? HF is a strong acid and will almost fully dissociate into H+ and F- in water. I would also expect some dissociation when in benzene. As such, your current model of dissolved HF is not very realistic.
>>
>>
>>Kind regards,
>>Thom
>>
>>
>>On Thu Feb 13 '14 6:33am, David G. wrote
>>----------------------------------------
>>>Hi

>>>As a test to understand how Firefly does compute and consider solvent effects the free energy of HF diatomic molecule has been calculated in gaseous state, water, and benzene to compare the results.

>>>free energy of HF (gaseous) : -100.426656 - 18.394/2625.5 = -100.433662 H
>>>free energy of HF (water): -100.433893 H
>>>free energy of HF (benzene): -100.430009 H

>>>we expected a larger difference between the values in water and benzene since HF is a highly polar molecule. I have attached the input/output files and I appreciate any comment to help us how to improve the results if it looks unwise in this state. Many Thanks
>>>
>>>
>>>Sincerely, David
>>>
>>>
>>>
>>>
>>>
>>>


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