Para red

Para red
Names
	Preferred IUPAC name 1-[(E)-(4-Nitrophenyl)diazenyl]naphthalen-2-ol
	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, 1-[(E)-(4-Nitrophenyl)diazenyl]-2-naphthol, paranitraniline red, Pigment Red 1, C.I. 12070, Recolite Para Red B, Carnelio Para Red BS
Identifiers
CAS Number	6410-10-2 [PubChem];
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL1967257;
ChemSpider	13544963 ;
ECHA InfoCard	100.026.449
EC Number	229-093-8;
PubChem CID	22917;
UNII	D54Q24K2EI ;
CompTox Dashboard (EPA)	DTXSID1052325 ;
	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
Molar mass	293.282 g·mol−1
Appearance	Red solid
Melting point	248 to 252 °C (478 to 486 °F; 521 to 525 K)
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Para red (paranitraniline red, Pigment Red 1, C.I. 12070) is a dye. Chemically, it is similar to Sudan I. It was discovered in 1880 by von Gallois and Ullrich and was the first azo dye. It dyes cellulose fabrics a brilliant red color, but is not very fast. The dye can be washed away easily from cellulose fabrics if not dyed correctly. Acidic and basic stages both occur during the standard formation of Para Red, and acidic or basic byproducts may be present in the final product.

Synthesis

Para red is prepared by diazotization of para-nitroaniline at ice-cold temperatures, followed by coupling with β-naphthol:^[1]

Regulation

Para red is not approved for use in food in any jurisdiction. In 2005, Old El Paso dinner kits were found to be contaminated with the dye and removed from supermarket shelves.^[2]^[3]

References

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

External links

MSDS at Oxford University

[1] Williamson, Kenneth L. (2002). Macroscale and Microscale Organic Experiments, Fourth Edition. Houghton-Mifflin. ISBN 0-618-19702-8.

[fsa-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.

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