Re: ORGLIST: basicity of C=O vs. P=O

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From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Tue Mar 20 2001 - 09:04:54 EST


Hello Eli,

It seems to me that this is a difficult question on various accounts:

1. If you have an aqueous solution protonation of carbonyl may catalyze in
certain cases enolization or diol formation, while I'm not aware of of
similar processes taking place with phosphoryl.

2. Knowing pKa's of carbonyl and phosphoryl compounds of similar structure
may not be enough for a decision when both groups are on the same molecule.
If the groups are close enough to each other they may strongly affect the
basicities by mutual inductive or conjugative effects.

3. If the stereochemistry is favorable you may be unable to tell where was
the proton attached due to hydrogen bonding between the groups.

You may find relevant information in the carbonyl and phosphoryl volumes of
Patai's series "The chemistry of functional groups," as they usually have a
chapter on acid-base properties.

All the best,

Jacob

At 9:22 20/3/1, eli breuer wrote:
>Hello everybody,
>
>I need pK data which could predict the site of monoprotonation in a
>molecule which contains a carbonyl, C=O, and a phosphoryl P=O group (in
>other words the basicities of the two groups).
>
>Eli Breuer
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