Sunday, August 19, 2012

Color and Para Red

In this post I'll talk about a little chemistry regarding color(s) and Synthesis of the Dye Para Red from Aniline

First some info from WIKI:
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.
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". [2]
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.[2] 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.[3]

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             All procedures were carried out under a hood, all individuals involved wore nitile gloves and safety goggles. Glassware was cleaned, rinsed with deionzed water and if necessary acetone before usage.
            First .7 grams para-Nitroaniline, 15 mL H2O were placed in an Erlenmeyer  flask. The flask was placed onto a hot plate and 3 M HCl was added till everything was completely dissolved. Upon dissolving the solution was cooled in ice water bath (0-5°C) for 10 minutes. Meanwhile a solution of 7 % NaNO2 was prepared by adding .7 grams NaNO2 to 10mL H2O and swirled for 10 minutes with stir bar via the use of the stir function on the hot plate. The heating function was turned off on the hot plate and the solution was kept cool during the period of the stirring.
            Next .7 grams KI were weighed and placed in a beaker. Via the use of a pipette 5.0mL of the cold diazonium salt was added to the KI. The mix was swirled till gas evolution decreased and then ceased. The solid was isolated via vacuum filtration with a Hirsch funnel and washed twice with 1mL portions of cold deizonized water. After filtration the product was isolated and kept for a week allowing it to dry.

            In another 50 mL beaker .25 g b-naphthol and 15mL water were heated till about 60-80°C. Next 10% NaOH was added drop wise will all was dissolved. Meanwhile a notch was cut in the wool portion of the fabric (to help with identification). The fabric was soaked in the solution for about 2 minutes, then removed with forceps and patted dry. The fabric was then placed in the cool diazonium salt.
            Once the fabric was removed the remainder of the b-naphthol was chilled till about 5°C. After cooling the remainders of the 2 solutions were mixed together and via the use of a Buchner funnel underwent vacuum filtration. The collected product was washed thoroughly with water. Once the product was collected it was placed in a beaker and allowed to sit for a week to dry. After the products dried the melting point range was observed and analyzed

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