EIDt: Got ya!
| Quote: | | "FD&C Yellow N° 5 (Tartrazine, color index N° 19140) is a monoazo dye having pyrazoline ring structure. It is synthesized by condensing
phenylhydrazine-p-sulfonic acid with oxalacetic ester. This reaction product is then coupled with diazotized sulfanilic acid. The resulting ester is
then hydrolyzed with sodium hydroxide. Alternatively, tartrazine can also be synthesized by condensing two moles of phenylhydrazine-p-sulfonic acid
with 1 mole of dihydroxytartaric acid. FD&C Yellow N° 5 is an orange yellow powder. It is readily soluble in water, yielding golden yellow
solutions." |
From the Handbook of Food toxicity.
Looks more simple than what I would have though! I guess you need to wok your way to phenylhydrazine-p-sulfonic acid.. Which I think can be made my
reacting diazotized p-sulfanilic acid with sodium sulfite.
PS: you should look in the site library at the dye chemistry books availble. I'm sure you will find further info over there, especially on the
preparation of the precursors an general process. There also lots of info in the google books!
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