Re: do acids act as anti-oxidants ?


<andrewvecsey@xxxxxxxxxxx> schrieb im Newsbeitrag
news:1132910245.984204.265420@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Yes you are right. To rephrase the question.... When bases release OH-,
> do these OH-s nutralize the "damages" caused by oxidizing agents that
> tear or rob electrons from molecules.

No, in general they don't.
Think of it this way: damage done by oxidizing agents is usually
peroxidation, the formation of epoxides, and/or breaking of the molecule
chain, and/or chemical addition of different radicals leading to a stable
molecule.

Its easier to estimate probabilities when you look at the molecule and its
electron configuration.

Oxygen:

..O. one unpaired electron on either side

(thats why oxygen is usually found in the more stable form O2 - that is O=O
which means each of the two oxygens shares two unpaired electrons making 2
covalent bonds to 2 electrons each)

Hydrogen:

H. one unpaired electron

a clearer (though a little to simplified) display can be found here:
http://www.krysstal.com/images/chembond_atom3.jpg

OH- means " :O:H " that is 2 electrons shared between hydrogen and oxygen
and one extra electron pairing the single electron on the other side.. thus
the "-" charge.

In order to act as a quencher the molecule should be able to add one more
electron to its structure and still be a (somewhat) stable molecule, OH-
already has one added to it, so its not really reactive in that way.

Most antioxidants have a few conjugated doublebonds.. these can transport
the "radicalic" electron to the end of the chain, thus stabilizing the
molecule and making it less reactive.

> Can bases act as ant-oxidizing agents in this way?
> regards

Antioxidants in biological systems are usually seen in the light of slowing
or terminating radical chain reaction.
In so far the release of OH- ions has no effect in any way to my best
knowledge.
(Although I would not rule out that pH value can have some effect on radical
chain reactions or the reactivity of certain metabolites)

> andrew vecsey.
>


.

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