[Timur992j]

Hello,

I noticed the following during an experiment:

When mixing L-proline (powder) and ascorbic acid/vitamin C (powder), the following reaction occurred within a few hours/days:

Initially within about 1 day a discoloration to pink, also an unpleasant odor (towards swimming pool/chlorine). In the further course (1-2 days) the color changed to yellow or brown and the mixed powders liquefied to an ultimately brown liquid (smell of washed rice)

Apparently it is not simply an oxidation of the vitamin C, as this does not actually turn pink and without proline the vitamin C powder remains unchanged.

Does anyone have an explanation?

Many thanks in advance!

[Babcock_Hall]

I do not know the answer to your question.  However, a low concentration of a colored substance can easily be seen.  In other words, you might be observing a contaminant of some kind.

[rolnor]

You have bacteria to consider and since you dont chemically analyze any product its impossible to answer. But its nice to make experiments even so, keeping your interest in chemistry alive. When I started doing chemistry I mixed everything I had and distilled the mixture, then checked the smell of the distillate, I was 12 years old

[Babcock_Hall]

Some proline residues in the protein collagen are converted into hydroxyproline residues (you may know this already).  Vitamin C has an indirect, but critical role in supporting this process.  It is quite unlikely that free proline is being converted into hydroxyproline in your experiment.  I am almost certain that hydroxyproline is colorless, for one thing.

[rolnor]

Some proline residues in the protein collagen are converted into hydroxyproline residues (you may know this already).  Vitamin C has an indirect, but critical role in supporting this process.  It is quite unlikely that free proline is being converted into hydroxyproline in your experiment.  I am almost certain that hydroxyproline is colorless, for one thing.

But you need enzymes for this, or?

[Babcock_Hall]

Yes, the enzyme prolyl hydroxylase.  Even if this enzyme were present, it might not act on free proline, as opposed to prolyl residues within the polypeptide.  I only mentioned this as background information, but perhaps it was confusing to do so.

[rolnor]

ok