Azo Dye Lab Report

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INTRODUCTION

Dyes exist in natural and synthetic forms in the world; they are used for the purpose of changing colors of different materials. William Perkins first discovered the azo dye on accident after adding alcohol to a product in the lab. They have the ability to do this due to the molecules of the dyes possessing conjugation. Conjugation is defined as p-orbitals overlapping which causes the electrons within to be delocalized; it is also seen in molecules and compounds that contain alternating double bonds. Systems that possess conjugation absorb energy in the ultraviolet-visible region of the spectrum to cause excitement of electrons and the transitions. When the electrons get excited, they jump from lower energy levels, to an excited
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The dye is called “azo” because of the nitrogen-nitrogen bond that is present. More specifically, the dye is called the azo-violet dye. The azo-violet dye molecule has a large and rather big conjugated system. To form the desired product, two reactions/mechanisms were conducted. The first reaction conducted consisted of reacting an aromatic amine ring and nitrous acid to produce a diazonium salt; the reaction is called diazotization. The reaction proceeding this was using the diazonium salt to couple with an activated arene to create the final product; this reaction is called diazonium …show more content…
An activated aromatic ring was needed, and this was where resorcinol came into play; due to its having two hydroxyl groups, it qualified. This solution was placed in an ice water bath; this was necessary as it lessened the amount of side reactions that had a chance of occurring. While the stir bar was stirring to ensure homogenous solution, the salt solution was poured in slowly. This was continued for thirty minutes and then sodium acetate was used to neutralize the solution (pH 5-6) and this took around thirty minutes; after this was over, the product was vacuum filtered and rinsed with slightly cold water. The product, observed qualitatively, was bright orange-red color. The reason for this color and not the azo-violet color presumed, was due to absorption of wavelengths. In acidic environment, the azo-violet has absorption tendency of 400nm, and reflects orange. This is because it is able to be protonated or undergo protonation. By being protonated, the resonance frequencies are changed/altered, which in turns lessen the conjugated system’s effects. This increases the energy needed to be absorb to make an electron excited. The product was turned into azo-violet color after the sodium acetate was used to neutralize the product, because under basic environment, the azo-violet absorbs wavelengths of 500-600nm, and reflects

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