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Para red

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Para red
Names
IUPAC name 1--2-naphthol
Other names 1-((4-Nitrophenyl)azo)-2-naphthalenol, 1-((4-nitrophenyl)azo)-2-naphthol, 1-((p-nitrophenyl)azo)-2-naphthalenol, 1-((p-nitrophenyl)azo)-2-naphthol, paranitraniline red, Pigment Red 1, C.I. 12070, Recolite Para Red B, Carnelio Para Red BS
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.026.449 Edit this at Wikidata
EC Number
  • 229-093-8
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C16H11N3O3/c20-15-10-5-11-3-1-2-4-14(11)16(15)18-17-12-6-8-13(9-7-12)19(21)22/h1-10,20H/b18-17+Key: WOTPFVNWMLFMFW-ISLYRVAYSA-N
  • InChI=1/C16H11N3O3/c20-15-10-5-11-3-1-2-4-14(11)16(15)18-17-12-6-8-13(9-7-12)19(21)22/h1-10,20H/b18-17+Key: WOTPFVNWMLFMFW-ISLYRVAYBR
SMILES
  • O=N(=O)c1ccc(cc1)/N=N/c2c3ccccc3ccc2O
Properties
Chemical formula C16H11N3O3
Appearance Red solid
Melting point 248 - 252 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Para Red (paranitraniline red, Pigment Red 1, C.I. 12070) is a chemical dye. Chemically, the dye is similar to Sudan I. The dye was discovered in 1880 by von Gallois and Ullrich, and was the first azo dye. It dyes cellulose fabrics a brilliant red, but is not very fast. The dye can be washed away easily from cellulose fabrics if not dyed correctly. Throughout making Para Red, the solution will become acidic and basic. Small amounts of byproducts may be left over after the Para Red dye is made that may be acidic or basic, but if made correctly there are little of these and the byproducts have no effect.

Synthesis

Para Red is prepared by diazotisation of para-nitroaniline at ice-cold temperatures, followed by coupling with β-naphthol:

Synthesis of Para Red
Synthesis of Para Red

UK food alert

In the United Kingdom, the dye is not permitted in food. The UK's Food Standards Agency (FSA) stated that "the Agency’s independent scientific experts have advised that, although there are very limited data available, it would be prudent to assume that it could be a genotoxic carcinogen".

On 21 April 2005, the FSA announced that some batches of Old El Paso dinner kits had been contaminated with the dye, and issued an alert. Also, reported on the 5 May 2005, the dye was found in 35 products which have now been taken off supermarket shelves. The products were mainly cooking sauces, though some are also spices.

References

  1. Williamson, Kenneth L. (2002). Macroscale and Microscale Organic Experiments, Fourth Edition. Houghton-Mifflin. ISBN 0-618-19702-8.
  2. ^ "Old El Paso Dinner Kits for enchiladas and burritos found with illegal dye" (press release). Food Standards Agency. 21 April 2005.
  3. "Banned dye found in more products". BBC News. 5 May 2005.

External links

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