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Sorry for my mistake there is not indeed any K-Oor Na-O bond, but the
organic mechanism of saponification could suggest an interaction of K+ or
Na+ with the charged oxygen in the intermediate (thus stabilisation of the
intermediate). It is not so easy to say if it hasn't an effect...Anyway KOH
works better for me now. It depends also on what oil you use, costs and on
many other things.
Step 1:
The hydroxide nucleophiles attacks at the electrophilic C of the ester
C=O, breaking the p bond and creating the tetrahedral intermediate.
Step 2:
The intermediate collapses, reforming the C=O
results in the loss of the leaving group the alkoxide, RO-, leading to
the carboxylic acid.
Step 3:
An acid / base reaction. A very rapid equilibrium where the alkoxide,
RO- functions as a base deprotonating the carboxylic acid, RCO2H, (an
acidic work up would allow the carboxylic acid to be obtained from the
reaction).
----- Original Message -----
From: "bob allen" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, January 14, 2005 6:13 PM
Subject: Re: [Biofuel] Kaliumhydroxide.
> Let me take a shot at this, even though inorganic chemistry is not my
> forte.
>
> <INORGANIC> Both KOH and NaOH are strong bases, meaning they ionize
> completely in water to metal cations and hydroxide anions. Hence the
> K-OH or Na-OH bond is ionic. In a sense you may say that one is more
> polar on the basis of the fact that Potassium is more electropositive than
> Sodium (K is below Na in the periodic chart) . This means that the
> difference in the Pauling electongativities of Potassium and Oxygen is
> greater than for the Sodium oxygen pair. </INORGANIC>
>
> All that having been said, I don't think that there is any difference in
> degrees of saponification EXCEPT for the fact that commercial NaOH
> contains about 15 per cent water, where as KOH can be had with less than
> 8 per cent water. Without that excess water in the system there will be
> little saponification. That is why you need to be sure and remove as much
> water as possible from WVO before doing the transesterifcation with
> alcohol.
>
>
>
>
> Andrew Cunningham wrote:
>
>>I would like to get a copy of those article. Can you explain what you
>>mean by the K-O bond being more polar? I didn't think that there were
>>any K-O bonds left once the KOH is dissolved (reacted) with the
>>methanol creating methoxide since that acid-bace reaction is quite
>>complete.
>>
>>Andy
>>
>>
> --
>
> ------------------------------------------------------------------
> Bob
> /ozarker.org/bob
> ------------------------------------------------------------------
> -----------------------------------------------------------------
> The modern conservative is engaged in one of Man's oldest exercises
> in moral philosophy; that is, the search for a superior moral
> justification for selfishness
> --------------------------------------------------------------------
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