Thesis Abstract

Abstract
Azo dyes are important compounds widely used in the textile, food, and pharmaceutical industries due to their vivid colors and ease of synthesis. In this study, an azo dye was synthesized from 2,4-dinitroaniline, 3-amino-5-methylpyrazole, and Byroscarpus coccineus. The synthesis process involved the diazotization of 2,4-dinitroaniline followed by coupling with 3-amino-5-methylpyrazole to form the azo dye. Byroscarpus coccineus was used as a natural source of the diazotizing agent to promote a greener and more sustainable approach to dye synthesis. The reaction progress was monitored using thin-layer chromatography (TLC) and the final product was characterized using UV-Vis spectroscopy and infrared spectroscopy (IR). The UV-Vis spectrum exhibited a distinct absorption peak characteristic of azo compounds, confirming the successful formation of the azo dye. The IR spectrum showed peaks corresponding to the azo linkage and other functional groups present in the dye molecule. The synthesized azo dye exhibited good solubility in common organic solvents and demonstrated excellent color strength, indicating its potential application as a dye in various industries. The dye was also tested for its dyeing properties on cotton fabric, showing good dye uptake and color fastness under different washing conditions. Overall, the synthesis of the azo dye from 2,4-dinitroaniline, 3-amino-5-methylpyrazole, and Byroscarpus coccineus proved to be a successful and environmentally friendly process. The use of natural sources for diazotization not only reduces the reliance on harsh chemical reagents but also offers a sustainable alternative for azo dye synthesis. The characterization results confirmed the formation of the azo dye, which exhibited desirable properties for potential industrial applications. This study contributes to the growing interest in green chemistry approaches for dye synthesis and highlights the potential of natural sources as alternatives to traditional chemical methods. The synthesized azo dye shows promise for use in various industries, particularly in textiles, where color intensity and fastness are crucial factors. Further research can focus on optimizing the synthesis process and exploring the application of the azo dye in different materials to fully assess its potential in commercial settings.

Thesis Overview

INTRODUCTION

1.1           Background of Study

 Azo compounds are a class of chemical compounds that are continuously receiving attention in scientific research (Kirkan, 2008; Otutu, 2013, Seferoglu, 2009). Azo dyes contain one or more azo groups (-N =N-) which are linked to SP2 hybridized carbon atoms, based on the number of such groups (Zollinger, 1991). The dyes known as monoazo dyes have only one (-N = N -) group while diazo and triazo dyes contain two and three (-N = N -) group, respectively.

The azo groups are generally connected to benzene and naphthalene rings, but can also be attached to aromatic heterocycles or enolizable aliphatic groups (Hunger, 2000).Synthetic dye manufacturing started in 1856, when the English chemist W.H. Perkin, in an attempt to synthetize quinine, obtained instead a bluish substance with excellent dyeing properties that later became known as aniline purple, Tyrian purple or mauveine. Henry Perkins 18 years old patented his invention and set up a production line. This concept of research and development was soon to be followed by others and new dyes began to appear on the market, a process that was strongly stimulated by Kekules discovery of the molecular structure of benzene in 1865. In the beginning of the 20th century, synthetic dyestuffs had almost completely supplanted natural dyes (Welham, 2001). The synthesis of most azo dyes involves diazotization of a primary aromatic amine, followed by coupling with one or more nucleophilic aromatic compound such as an aryl amine or a phenol (McCorthy, 1997). Azo dyes are the most important class of industrial dyes, both in number and amount. In addition, azo dyes have found wide application in dyeing wool, polyamide fiber, semi conductivity textile and food industries (Bluss, 1995). In the present study a new azo compounds was prepared and Identification by IR, UV–Visible spectroscopy was carried out.

1.2           Objectives of the Study

The objectives of work are to

1. synthesize azo dyes from 2,4,­­- dinitroaniline and 3­- amino ­-5- methylpyrazole
2. characterize the dyes using Infra-red spectroscopy and UV­­­­­­­­­­­­- visible spectroscopy

1.3           Colour and its Chemical Constitution

After the synthesis of mauviene in 1856 by Henry Perkins, little was known of the chemistry of dyes and the constitution of mauviene was not established. However, following kekul’s proposal concerning the structure of benzene in 1865 which lead to theories concerning the influence of organic structures on the colour of molecules began. Graebe and Lieberman in 1867 observed that organic dyes know then were unsaturated compounds and that this unsaturation is destroyed by reducing agent which causes them to decolourise.

Witt 1876 put forward a theory that the colour of a substance is mainly due to the presence of an unsaturated group called chromophores (Greek chroma – colour, phores – bearing).the important chromophores are the nitro(-NO2), Carbonyl (-C=O), azo (-N=N-), nitroso (-C=N-) the quinoid rings. He named the compounds containing chromphores chromogen. this chromogen do not behaves as dyes fibers unless they are also substituted by basic or weakly acidic groups called auxochromes e.g. -NH2, and OH .The presence of these groups increases the colour yielding power of the chromophore.