ChemAxon Forum Archive » Structure based predictions: Calculator Plugins & Chemical Terms

phosphonium salt acidity

User 870ab5b546

10-04-2009 19:51:09


[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



User 851ac690a0

10-04-2009 20:39:36

Hi,


 


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


 


 


 


Jozsi


 

User 870ab5b546

10-04-2009 23:29:47

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?  

User 851ac690a0

10-04-2009 23:42:11

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


 

User 870ab5b546

10-04-2009 23:50:32

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.

User 851ac690a0

11-04-2009 00:05:53

Hi,


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


Jozsi