Subject: Re: CCL:pKa calculation (2)

From: [email-masked] (Per-Ola Norrby)
Date: Wed, 27 Nov 1996 22:58:39 +0100

Dear Emad,

>Now is it possible to convert the obtained difference, even very rough, to pH
>units?  For example is there anything like "1Kcal can be related to .6 pH
>unit"?

        Sure, since .Delta.G = -RT ln(Ka) and pKa = -log(Ka), it follows that

        .Delta.G = RT ln(10) pKa

        Therefore, for the reaction AH+ + B <-> A + BH+ :

        .Delta.G = RT ln(10) .Delta.pKa

        I would still add a semi-empirical solvation term to .Delta.G, as
the conformers may be solvated differently.

        Regards,

        Per-Ola Norrby

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 *  Per-Ola Norrby
 *  The Royal Danish School of Pharmacy, Dept. of Med. Chem.
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