Dye Lab - Amy Linkous CHEM 2556 CRN 91653 Synthesis of...

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Amy Linkous 9/21/09 CHEM 2556: CRN: 91653 Synthesis of Methyl Orange and Dyeing Objective: To synthesize an azo dye and use it along with previously made dyes in dyeing studies with natural and man-made fibers treated with varying mordants. General Reaction: Diazotization: 2R-N + H 3 + Na 2 CO 3 → 2R-NH 2 + CO 2 + H 2 O R-NH 2 + 2 HCl + NaNO 2 → R-N + N + 2NaCl + 2H 2 O Azo Coupling: Procedure: Part 1: Synthesis of Methyl Orange
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4.8 g of sulfanilic acid monohydrate was dissolved in 50 mL of boiling 2.5% sodium carbonate solution. The solution was cooled under running tap water and 1.9 g of sodium nitrite was added with stirring. Once the sodium nitrite dissolved, the solution was poured into a beaker containing about 25 g of ice and 5 mL concentrated hydrochloric acid was added. In about one minute the white diazonium salt precipitated out of solution. This product was not collected but was used while still in suspension. 3.2 mL dimethylaniline and 2.3 mL glacial acetic acid were thoroughly mixed in a test tube and this new solution of dimethylaniline acetate was added to the suspension of diazonium sulfanic acid, with stirring. The test tube was rinsed with a small amount of water and the rinse was added to the beaker. The solution was stirred thoroughly and a red color was observed. The solution formed a stiff paste within a few minutes. 33 mL of 3 M sodium hydroxide solution was then added to produce the orange sodium salt. This was stirred thoroughly and heated to boiling, when the dye dissolved. The beaker was then removed from heat and placed in an ice bath, where it cooled undisturbed for about 10 minutes until cool to the touch. The product was then collected by suction filtration using a Büchner funnel. The beaker and filter cake were rinsed with saturated sodium chloride solution. The product did not need to be dried before use in the dye bath.
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