Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: shalikadm on June 22, 2012, 03:18:32 PM

Title: Which are the most acidic ?
Post by: shalikadm on June 22, 2012, 03:18:32 PM
(http://s17.postimage.org/7suc94zfz/image.png)
In the first one there's two deactivators while the second one has only one.But the second one has more electronegative element F as the deactivator..So how can I choose the most acidic ?
Title: Re: Which are the most acidic ?
Post by: Nescafe on June 22, 2012, 03:42:46 PM
I would say the dichloro due to the fact that the electronegativity of F is about 4.0, that of Cl is 3.0. There is one unit difference but there are two Cls v.s. one F. I do not think they are much different though.
Title: Re: Which are the most acidic ?
Post by: orgopete on June 22, 2012, 06:43:09 PM
The chloropropionic acid should be more acidic. I compared the dichloro with monofluoroacetic acids and the dichloroacetic acid was more acidic, 1.29 vs 2.66, see http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf

Title: Re: Which are the most acidic ?
Post by: cheese (MSW) on June 23, 2012, 12:26:41 PM
CH3CCl2CO2H 2,2-dichloropropionic acid   pKa = 1.68
CH3CHFCO2H  2-fluoropropionic acid    pKa = 2.68
CAS