[Brainless]

While doing research on colouring agents used in food and cosmetics in the EU I stumbled upon cochineal (or carminic acid, carmine, E120). I read about the synthetic substitute which is labeled E124 (E numbers are approved by the Europian Union). To my surprise it's banned in the USA. Can anyone explain to me why it is banned?

also: The structures of the natural and synthetic version aren't very analogous, why is cochineal red A called the synthetic version of cochineal? Is it only because they absorb light at the same wavelength?

[Enthalpy]

https://en.wikipedia.org/wiki/Ponceau_4R#Health_effects
https://de.wikipedia.org/wiki/Cochenillerot_A#Gesundheitliche_Aspekte

There are zillions of compounds but only a handful of colours.

[Brainless]

Yeah I've read the wikipedia pages but as usual they aren't a great help haha, apparently the threat of it being carcinogenic is reason for America's health and safety department to completly ban it?

Also I've ran into more questions so if anyone has the time to answer them OR brainstorm about them with me I'd appreaciate it greatly!

I've read that:
1) Carmic acid would turn orange in low pH solutions?
2) That the structure of carmic acid is great for bonding metal complexes but what makes it so great? I know it has to do with the double bounded oxygen but I can't really tell why this would be great for bonding with aluminium.
3) They cook the carmic acid in ammonia and sodium carbonate. I understand the ammonia makes carmic acid -> 4-amino-carmic acid but why the sodium carbonate? sodium and carmic acid make an insoluable salt, but I don't understand how, where would sodium fit in? and Why?

[Babcock_Hall]

With respect to (1), see a note at https://pubchem.ncbi.nlm.nih.gov/compound/Carminic-acid

[Brainless]

not a lot of talkative people huh?

I've already visited that website as it is the first hit on google when you search for carminic acid....

I didn't find why it changes colour in acidid solutions but I found the answer on a different website.

I didn't find why carminic acid is great for bonding metal complexes. And I would still like to know.

I DID find why they use sodium carbonate.
"Bright-red, light pieces, easily reduced to powder; practically insoluble in cold water or dil acid; partly soluble in hot water; soluble in borax, alkali hydroxides and alkali carbonates giving deep red solutions" 
So it's technically just a solvent. This still rises the question why it is a good solvent.

[AWK]

I expect that it changes color in the basic solution too. The only problem at which pH.

Compare complexes of alizarin.

Check reactions of phenols with bases (qualitative test in organic chemistry)

[Brainless]

I have found that it changes gradually because the phenol groups react with the base and in water, in acidic solutions it turns orange (lack of free electron pairs so less chromofore groups) and violet in a basic solution (too many free electron pairs, a lot of chromofore groups)

So you were spot on with the phenols!

That leaves me with these questions:
That the structure of carmic acid is great for bonding metal complexes but what makes it so great? I know the double bonded oxygen and phenol groups have lone electron pairs (negative) and aluminum is a positive ion but is that the only reason it forms metal complexes easily?

Alizarin is build from the same quinone, they are actually quite similar I'm gonna read more about it tomorrow