ABSTRACT
Twelve different monoazo heterocyclic disperse and acid dyes of low molecular weight derived from 2-aminothiophene and conventional amines as diazo components were successfully synthesized. The identities of the synthesized dyes and intermediates were investigated using spectroscopic analysis such as Uv-visible spectrometry, Fourier Transform Infrared Spectrometry and Gas Chromatography Mass Spectrometry. The 2-aminothiophene intermediates and heterocyclic disperse dyes were synthesized using the Gewald‟s method and the molar mass of the synthesized intermediates were between 257-285 g/mol while that of the synthesized dyes were between 305-614 g/mol. All the synthesized dyes absorbed within the visible region of the electromagnetic spectrum but the heterocyclic disperse dyes synthesized from the 2-aminothiophene intermediates were more bathochromic than those of the conventional amines dyes. The heterocyclic disperse dyes gave good exhaustion ranging from 60 % to 78 % on polyester fabric while the acid dyes on chrome tanned leather gave an excellent exhaustion of 80 % to 87 %. The dyes gave mostly brown, deep purple and orange shades and exhibited good to excellent fastness properties on the dyed substrates. For wash fastness, it was between 5 (excellent) and 3 (good), while for light fastness it was between 6 (good) and 4 (moderate). The antimicrobial screening of the synthesized dyes against six (6) different microorganisms were assessed using the Agar Well diffusion method and the results showed zones of inhibition ranging from 3-34 mm, Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) values as low as 12.5 mg/ml, which indicate that the dyes can be effective against infectious diseases which these microorganisms can cause.
TABLE OF CONTENTS
TITLE PAGE………………………………………………………………..…………………..i
DECLARATION ……………………………………………………………………………………………………….. ii
CERTIFICATION ……………………………………………………………………………………………………. iii
DEDICATION ………………………………………………………………………………………………………….. iv
ACKNOLEDGEMENT ………………………………………………………………………………………………. v
ABSTRACT ……………………………………………………………………………………………………………… vi
TABLE OF CONTENTS…………………………………………………………………….vii
LIST OF TABLES … …………………………………………………………………………vii
LIST OF FIGURES …. ……………………………………………………………………….xii
LIST OF SCHEME………………………………………………………………………. … xiii
LIST OF APPENDICES …………………………………………………………..………..xiv
CHAPTER ONE ………………………………………………………………………………………………………… 1
1.0 INTRODUCTION ……………………………………………………………………………………………. 1
1.1 Azo Dyes ………………………………………………………………………………1
1.1.1 Disperse Dyes …………………………………………………………………………3
1.1.2 Acid Dyes ……………………………………………………………………………..3
1.2 Statement of the Research Problem ……………………………………………………3
1.3 Justification ……………………………………………………………………………4
1.4 Aim and Objectives of the study ………………………………………………………4
CHAPTER TWO ………………………………………………………………………………6
2.0 LITERATURE REVIEW ……………………………………………………………..6
2.1 Development of Synthetic Dyes ………………………………………………..…………6
2.1.1 Basic dyes ……………………………………………………………………………….9
2.1.2 Vat dyes (Indigoid) …………………………………………………………………….10
2.1.2.1 Anthraquinone vat dyes ………………………………………………………………11
2.1.2.2 Solubilised vat dyes ………………………………………………………………….11
2.1.3 Sulphur dyes ……………………………………………………………………………11
2.1.4 Direct dyes ……………………………………………………………………………..12
2.1.5 Phthalocyanine dye ……………………………………………………………………13
2.1.6 Azoic dyes ……………………………………………………………………………..13
2.1.7 Acid dyes ………………………………………………………………………………14
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2.1.8 Metal Complex dyes ……………………………………………………………………15
2.1.9 Disperse dyes …………………………………………………………………………..15
2.1.10 Reactive dyes …………………………………………………………………………17
2.2 Azo dye synthesis ………………………………………………………………………..18
2.3 Heterocyclic Disperse Dyes ……………………………………………………………..21
2.4 Fibre Structure in Relation to Dyeing ……………………………………………………22
2.5 Dyes and their Required Properties ………………………………………………………23
2.6 Forces of Attraction between Dye and Fibres during Dyeing ……………………………23
2.6.1 Ionic Bonds (Ionic Forces) …………………………………………………………….24
2.6.2 Hydrogen Bonding …………………………………………………………………….24
2.6.3 Covalent Bonding ………………………………………………………………………25
2.6.4 Van der Waals Forces ………………………………………………………………….25
2.7 Hides and skins …………………………………………………………………………..26
2.7.1 Functions of Hides and Skins ………………………………………………………….26
2.7.2 Tanning …………………………………………………………………………………26
2.7.3 Tanning Procedure …………………………………………………………………….27
2.7.3.1 Vegetable tanning …………………………………………………………………….28
2.7.3.2 Mineral tannin (chrome tanning) …………………………………………………….28
2.7.4 Dyestuffs Available for the leather Industries …………………………………………29
2.7.5 Dyeing of Leather ………………………………………………………………………29
2.7.6 Dye selection for leather application …………………………………………………..30
2.8 Polyester Fibre ……………………………………………………………………………30
2.9 Dyes for polyesters ………………………………………………………………………31
2.10 Antimicrobial Dyes …………………………………………………………………….31
CHAPTER THREE ………………………………………………………………………….34
3.0 MATERIALS AND METHODS ……………………………………………………34
3.1 Materials …………………………………………………………………………………34
3.2 Apparatus and Equipment ……………………………………………………………….34
3.3 Synthesis of Aminothiophene Intermediates …………………………………………….34
3.3.1 Aminothiophene intermediate 1 ……………………………………………………….34
3.3.2 Aminothiophene intermediate 2 ……………………………………………………….35
3.4 Purification and Determination of some Physical properties of the Synthesized 2-Aminothiophene Intermediates ………………………………………………………………35
3.5 Procedure for Diazotization and Coupling ………………………………………………35
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3.5.1 Diazotization of Intermediates 1 And 2 ……………………………………………….35
3.5.2 Diazotization of Intermediate 3 ………………………………………………………..36
3.5.3 Diazotization of Intermediate 4 ………………………………………………………..36
3.5.4 Coupling Reaction ……………………………………………………………………..36
3.6 Purification of the Dyes ………………………………………………………………….37
3.7 Percentage Yield of Dyes and Intermediates ……………………………………………37
3.8 Characterization of the Synthesized Dyes and Intermediates ……………………………37
3.8.1 Melting Point Determination …………………………………………………………..38
3.8.2 Molar Extinction Coefficient ………………………………………………………….38
3.8.3 Determination of Visible Absorption Spectra …………………………………………38
3.8.4 FT-IR Determination …………………………………………………………………..39
3.8.5 Gas Chromatography-Mass Spectrometry (GC-MS) ………………………………….39
3.9 Application of Dyes ……………………………………………………………………..39
3.9.1 Dyeing of polyester ……………………………………………………………………39
3.9.2 Dyeing of leather ………………………………………………………………………40
3.10 Determination of Dyebath Exhaustion …………………………………………………41
3.11 Assessment of Fastness Properties ……………………………………………………..41
3.11.1 Wash Fastness Test …………………………………………………………………..41
3.11.2 Light Fastness Test ……………………………………………………………………42
3.12 Evaluation of the Antimicrobial Activity of Azo Dyes …………………………………42
3.12.1 Test organisms ……………………………………………………………………….42
3.12.2 Culture media …………………………………………………………………………42
3.12.3 Determination of inhibitory activity (sensitivity test) of the synthesized dyes using
Agar well diffusion method ………………………………………………………………….43
3.12.4 Determination of minimum inhibitory concentration (MIC) ………………………..43
3.12.5 Determination of minimum Bactericidal/fungicidal concentration (MBC/MFC) …..44
CHAPTER FOUR ……………………………………………………………………………45
4.0 RESULTS ……………………………………………………………………………45
4.1 Synthesis of 2-Aminothiophene Intermediates ………………………………………45
4.1.1 Synthetic Route for the 2-Aminothiophene Intermediates …………………………..45
4.1.2 Physical Properties of 2-aminothiophene Intermediates …………………………….45
4.2 Synthesis of the Azo Dyes …………………………………………………………..46
4.2.1 Synthetic route for the Synthesis of the Azo Dyes …………………………………..46
4.2.2 Physical Properties of the Synthesized Azo Dyes ……………………………………51
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4.3 Characterization of the Synthesized Intermediates and Dyes ……………………….51
4.3.1 Visible absorption Spectroscopy of Dyes ……………………………………………51
4.3.2 Infra-Red Spectra of the Intermediates and Dyes ……………………………………51
4.3.3 GC-MS of the Intermediates and Dyes ………………………………………………51
4.4 Antimicrobial Activity of the Synthesized Dyes …………………………………….51
4.5 Dyeing of Polyester Fabric and Chrome Tanned Leather ……………………………52
4.5.1 Dyeing Exhaustion of the Synthesized Dyes ………………………………………..52
4.5.2 Assessment of Fastness Properties to Washing and Light …………………………..52
4.5.2.1 Wash fastness ………………………………………………………………………..52
4.5.2.2: Light Fastness of the using 8 Blue Wool Standard …………………………………52
CHAPTER FIVE …………………………………………………………………………….64
5.0 DISCUSSION ……………………………………………………………………….64
5.1 Synthesis and Physical Properties of 2-aminothiophene Intermediate ………………64
5.2 Synthesis and Physical Properties of the Azo Dyes …………………………………65
5.3 Characterization of the Synthesized Intermediates and Dyes ………………………..66
5.3.1 Visible absorption spectroscopy of dyes in DMSO and Methanol ………………….66
5.3.2 The Infra-Red Spectra of the Intermediates and Dyes ………………………………69
5.3.3 GC-MS Spectra of the Synthesized Intermediates and Dyes ………………………..69
5.4 Antimicrobial Screening of the Synthesized Dyes …………………………………..70
5.5 Dyeing of Polyester Fabric and Chrome Tanned Leather ……………………………72
5.5.1 Dye Exhaustion on Polyester Fibre and Chrome Tanned Leather …………………..72
5.5.2 Wash Fastness of the Synthesized Dyes on Polyester Fibre and Chrome Tanned Leather using ISO 3 Standard ……………………………………………………….73
5.5.3 Light Fastness of the Synthesized Dyes on Polyester Fibre and Chrome Tanned Leather using 8 Blue Wool Standards ……………………………………………….74
CHAPTER SIX ………………………………………………………………………………75
6.0 SUMMARY, CONCLUSION AND RECOMMENDATION ………………………75
6.1 Summary …………………………………………………………………………….75
6.2 Conclusion ……………………………………………………………………………77
6.3 Recommendations ……………………………………………………………………77
CONTRIBUTION TO KNOWLEDGE ……………………………………………………..78
REFERENCES ………………………………………………………………………………79
CHAPTER ONE
1.0 INTRODUCTION
1.1 Azo Dyes
Azo compounds are a class of chemical compounds that are continuously receiving attention in scientific research (Kirkan and Gup, 2008; Seferoglu, 2009 Otutu et al., 2011). They are usually strongly coloured compounds which can be intensely yellow, red, orange, blue or even green, depending on the exact structure of the molecule. As a result of their colour, azo compounds are of tremendous importance as dyes and also as pigments for a long time (Ebenso et al., 2008). For a dye to be suitable for use, the colored material must have the following desirable properties: intense colour, solubility in water and substantivity for the substrate (Nkeonye, 1987). In fact, about half of the dyes in industrial use today are azo dyes, which are mostly prepared from diazonium salts (Robert et al., 2011; Zollinger, 2003). The structural features in organic compounds, that usually produce colour are >C=C<, –N=O, –N=N–, >C=O and –NO2. Most importantly, the groups that invariably confer colour are the azo (–N=N–) and nitroso (–N=O) while the other groups actually do so under certain circumstances (Abrahart, 1977). Furthermore, azo dyes have been studied widely because of their excellent thermal and optical properties in applications such as optical recording medium (Samieh et al., 2008), toner (Kirkan and Gup, 2008), ink-jet printing and oil-soluble light fast dyes (Gregory, 1990). Recently, azo compounds as organic dyes have also attracted attention due to their interesting electronic features in photoconductors (Yildiz and Boztepe, 2002). However, the traditional application field of the synthetic azo dyes still remains the textile industry, and the finishing of fibrous materials.
In recent years, several heterocyclic and non heterocyclic compounds are extensively used in azo dye chemistry for textile and non-textile applications (Katritzky and Rees, 1984). These dyes are now marketed to produce a full range of azo dyestuffs without the use of colorants based on hetero-aromatic diazo components. Most of the heterocyclic dyes are
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derived from the diazo components consisting of five-membered rings containing one or more nitrogen heteroatoms, with the rings being fused into another aromatic ring (Griffiths et al., 1984; Towns, 1999; Samieh et al., 2008; Otutu et al., 2011). The dyes with heterocyclic diazo components have been intensively investigated, to produce bright and strong colour shades ranging from red to greenish blue on synthetic and natural fibres. These results led to commercial products to replace the conventional azobenzene dyestuffs. The nitro substituted aminothiophenes, and aminothiazoles are primarily of importance as diazo components (Seferoglu, 2009). Non-textile uses of heterylazo disperse dyes have been explored, for example in reprographic technology, functional dye applications, and non-linear optical systems (Zollinger, 2003). The monoazo dyes containing heterocyclic rings or carbocyclic rings result in brighter and often deeper shades than their disazo or trisazo analogues. On the other hand, the disazo or trisazo dyes are very important in applications such as disperse dyes for polyester fibres, and as photoconductors (Otutu et al., 2011).
The past few decades have witnessed considerable innovation in the field of azo dye chemistry based on heterocyclic systems and studies in the synthesis of such derivatives have been reported (Alaa and Terek, 2006; Maradiya, 2010). Heterocyclic based azo dyes are not only important for their excellent properties as dyes for polyester textiles; they have also been utilized in non-textile applications such as photodynamic therapy, lasers, reprographic technology, functional dye applications and non-linear optical systems. Although a variety of heterocyclic and conventional azo benzene systems have been employed for the synthesis, there remains much scope for the design and development of new chromophores. Most of the recent research has focussed on structural variations of existing types, for example variations in substituents, especially on the side chains of the coupling components (Alaa and Terek, 2006; Maradiya, 2010)
.
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1.1.1 Disperse Dyes
Disperse dyes are sparingly water soluble dyes. The most important class of disperse dyes is the azo class. This class of azo disperse dyes may be further subdivided into four groups, the most numerous of which is the amino azo benzene class. This class can be altered to produce bathochromic shifts. A range of heterocyclic aminoazobenzene dyes are also available. These give bright dyes, and are bathochromically shifted to give blues. The third class of disperse dye is based on heterocyclic coupling components, which produce bright yellow dyes. The fourth class is disazo dyes. These tend to be quite simple in structure. Other than these, there are disperse dyes of the carbonyl class and a few from nitro and polymethine classes (Yusuf, 2012).
1.1.2 Acid Dyes
Acid dyes are water soluble dyes which are applied basically from acid solution onto fibres possessing basic nitrogen groups e.g. leather, wool, silk, nylon. The water solubility is as a result of the presence of sulphonic acid groups or in rare cases carboxylic acid groups. Acid dyes are found in nitrophenols, azo compounds, triphenyl methane, anthraquinoids or indigoid compounds (Recep, 2005). There are three kinds of acid dyes which are in accordance to their molecular mass and ease of levelling. Those of higher molecular mass which do not level easily (groups 2 and 3) are known as acid milling and neutral milling dyes (Nunn, 1979).
1.2 Statement of the Research Problem
Most of the conventional azobenzene dyes fall in the visible region of the spectrum and hence not sufficiently bathochromic and this place a limitation on the colours obtained. Therefore there is need to synthesize dyes that are highly bathochromic and possess good colouristic properties.
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The growth of micro-organisms on textile materials inflicts a range of negative effects not only on the fibre itself but also on the wearer. This is due to the fact that fibrous materials undergo biological degradation, and it seems that about 40 % of the damage is due to the effect of microorganisms.
In spite of decades of effort it has been difficult to obtain fibrous materials free of pathogenic microbes. To survive bacterial developed antibiotics mechanism, there is a great demand for new dyes with good colouristic and application properties, and also exhibiting biological activity.
1.3 Justification
Azo compounds are versatile molecules and have received much attention in both research, and application (Nejati et al., 2007).
Due to the smaller molecular size of the mono-azo dyes, they are expected to present good penetrability in fibre, and the exhaustion problem of acid and disperse dyes on fibres improved. This will reduce the amount of dyes left after dyeing, thus reducing the environmental pollution caused by the use of acid and disperse dyes (Hallas and Towns, 1997a).
The present study is focused on the possibility of developing new azo dyes with good colouristic and application properties, and exhibiting biological activity.
1.4 Aim and Objectives of the study
Aim
The aim of this research was to synthesize acid and disperse dyes using aminothiophene and conventional amine based diazo components and to study their application and antimicrobial properties.
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Objectives
The main objectives of the present study were:
1. To synthesize series of azo acid and disperse dyes based on 2-aminothiophene and conventional amines as diazo components, and with coupling components such as N,N-dimethylaniline, N,N-diethylaniline and dodecyl-pyridone.
2. To characterize the structure of the dyes using Uv-visible, FT-IR Spectrophotometry and GC-MS.
3. To investigate the dyeing properties of the synthesized heterocyclic disperse dyes on polyester fabric and acid dyes on chrome tanned leather.
4. To investigate the fastness properties of the dyed substrates to agencies such as washing and light.
5. To investigate the antimicrobial properties of the synthesized dyes against some selected bacteria and fungi such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida krusei, Candida albicans and Aspergillus niger.
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