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

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From: Jacob Zabicky (zabicky$##$
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,


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
>ORGLIST - Organic Chemistry Mailing List
>Website / Archive / FAQ:
>List coordinator: Joao Aires de Sousa (jas$##$


Prof. Jacob Zabicky Tel.
Institutes for Applied Research Fax. 972-8-6472969
Ben-Gurion University of the Negev Private: POB 12366, Beer-Sheva 84863
POB 653, Beer-Sheva 84105, ISRAEL Tel. 972-8-6496792


ORGLIST - Organic Chemistry Mailing List
Website / Archive / FAQ:
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