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phosphonium salt acidity
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Bob

Joined: 15 Jun 2004
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Link to postPosted: Fri Apr 10, 2009 8:51 pmPost subject: phosphonium salt acidity Reply with quote

[bob@epoch questionData]$ evaluate -e "apKa()" "CC[P+](c1ccccc1)(c2ccccc2)c3ccccc3" -p 4

;;;;33.7038;46.4158;;36.0612;48.3189;;34.2035;;;;36.7633;;34.6963;;;;37.3314

This result is incorrect.  C(2) is more acidic than C(5).
Happily, though, JChem is correctly calculating the acidity of phosphonates:
[bob@epoch questionData]$ evaluate -e "apKa()" "COP(C)(=O)OC" -p 4
33.7162;;;25.4933;;;35.7277

Jozsef
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Link to postPosted: Fri Apr 10, 2009 9:39 pmPost subject: Reply with quote

Hi,

 

pKa of C(2)=24.37 see attached figure.

 

 

 

Jozsi

 

Bob

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Link to postPosted: Sat Apr 11, 2009 12:29 amPost subject: Reply with quote

It would be helpful if you would explain the difference between my result and yours.  I didn't make up the result I posted, and I don't know why it differs from yours.  Can you reproduce my result, which was obtained using JChem 5.1.05?  

Jozsef
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Link to postPosted: Sat Apr 11, 2009 12:42 amPost subject: Reply with quote

Hi,

 

Oh,yes. I have used tha latest release candidate version: ( 5.2.1)

 

http://www.chemaxon.com/rc/marvin/release-notes.html
http://www.chemaxon.com/rc/marvin/download.html
http://www.chemaxon.com/rc/jchem

 

For phosphonate I obtained the same pKa values.

 

Jozsi

 

Bob

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Link to postPosted: Sat Apr 11, 2009 12:50 amPost subject: Reply with quote

Thanks.  And this result is not obtained in JChem 5.2.0, correct?  I went to the current Marvin at your Web site, 5.2.0, and it gave no value for the CH2 group.

Jozsef
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Link to postPosted: Sat Apr 11, 2009 1:05 amPost subject: Reply with quote

Hi,

Yes. This type of "CH2" will only appear in 5.2.1.

Jozsi

 

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