Contents History of DYES

DYE

Some Natural Dyes and their sources

Synthetic dye

Types of Dyes

Chemical Classification

Azo Dye

As Dyes and Pigments

Some Azo Dye Compounds and their structure

REQUIREMENTS

Para Red Dye

Names and Properties

Synthesis

Procedure and Observation

Fluorescent Dye

Resources Required

Procedure

Reactions

Observations

Bibliography

History of DYESDyestuffs are a branch of chemistry inspired by many people in history. The earliest written records of use of dyestuffs was found in China around 2600 B.C. Alexander the Great during his conquest of India in 327 B.C., mentions about the beautifully printed cottons that he saw during one of his expeditions. Around 1745, the dye INDIGO was grown in England, which was imported from India.

In 1868, a German chemist produced ALIZARIN, which was found to be useful as a synthetic substitute. In 1887, ALIZARIN YELLOW was used as a mordant dye. And 40 years later, Baeyer and Sunder had developed INDIGO SOL-O, which was a versatile dye that found various applications.

One cannot forget the contribution of Dupont International in the development of various kinds of dyes. By 1970s, the Ciba-Geigy introduced the CIBACRON-F series, which was considered to be the most recent development of time. Since then the dyestuffs created a new revolution in the world of colours.

DYE:

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber.

Some Natural Dyes and their sources

Colour/Class Name Source

Yellow/flavonoid Weld quercetin safflowerseeds, stems, leaves of Reseda luteolaNorth American oak bark, Quercus tinctoria nigradried petals of Carthamus tinctorius

Red/anthraquinoneKermes cochineal alizarininsects, Coccus ilicisinsects, Dactylopius coccusmadder plant roots, Rubia tinctorum

Blue/indigoid Indigo, woadindigo plant leaves, Indigofera tinctoria L.

Purple/indigoid Tyrian purplemollusks, Murex brandaris

Black/chroman Logwoodheartwood, Haematoxylon campechianum L.

Synthetic dyeThe first human-made (synthetic) organic dye, mauveine, was discovered serendipitously by William Henry Perkin in 1856. Many thousands of synthetic dyes have since been prepared. Synthetic dyes quickly replaced the traditional natural dyes. They cost less, they offered a vast range of new colors, and they imparted better properties to the dyed materials. Dyes are now classified according to how they are used in the dyeing process.

Dye typesIt distinguishes based on the process of application to various substrates. They are subdivided with examples as follows-

ACID DYES: They are salts of sulphonic acids and can be applied to wool, silk, polyurethane fibres and nylon.

Example: Orange-1, Methyl Orange.

BASIC DYES: They contain amino groups, which are acid form water-soluble salts. They attach themselves to the anionic sites on the fabrics. They are used as dye in reinforced nylons and polyesters.

Example: Malachite green, Congo red. DIRECT DYES: They are water-soluble and are directly applied to fabrics such as cotton, rayon, wool, silk and nylon that form hydrogen bonds with water.

Example: Martius yellow, Congo red.

DISPERSE DYES: These dye in the form of minute particles of suspension diffuse into the fabric. They are used for dyeing the synthetic fibres like polyesters, nylon and polyacrylonitrile. Example : Celliton fast pink B,Celliton fast blue B FIBRE REACTIVE DYES: They attach themselves to the fibre by an irreversible reaction. Dyeing is fast and colour is retained for a long time.

Example: 2,4 dichloro-1,3,5-triazine.

INSOLUBLE AZO DYES: They are directly synthesized on the fibre. The colour is not fast. They are used for dyeing cellulose, silk, polyester, nylon, polypropylene, polyurethane, polyacrylonitrile and leather.

Example: Nitroaniline red.

VAT DYES: They are water-insoluble and are reduced to leuco-form before dyeing by alkaline reducing agent. The fibre is then exposed to air or to an oxidizing agent after which the original insoluble dye is formed in the structure of the fibre.

Example: Indigo, Indigo Sol-O

MORDANT DYES: They are used for dyeing in the presence of metal ions. The metal ions bind to the fabric and the dye acting as a ligand coordinates with the metal ion. The same dye in the presence of different metal ions gives different colours.

Example: Alizarin gives rose red with Al3+, blue with Ba2+ Food dyes: One other class that describes the role of dyes, rather than their mode of use, is the food dye. Because food dyes are classed as food additives, they are manufactured to a higher standard than some industrial dyes. Food dyes can be direct, mordant and vat dyes, and their use is strictly controlled by legislation. Many are azo dyes, although anthraquinone and triphenylmethane compounds are used for colors such as green and blue. Some naturally-occurring dyes are also used.

Chemical classification

By the nature of their chromophore, dyes are divided into:

Category:Acridine dyes, derivates of acridine Category:Anthraquinone dyes, derivates of anthraquinone Arylmethane dyes

Category:Diarylmethane dyes, based on diphenyl methane

Category:Triarylmethane dyes, derivates of triphenyl methane Category:Azo dyes, based on -N=N- azo structure

Diazonium dyes, based on diazonium salts

Nitro dyes, based on a -NO2 nitro functional group Nitroso dyes, based on a -N=O nitroso functional group

Phthalocyanine dyes, derivatives of phthalocyanine Quinone-imine dyes, derivativees of quinone

Category:Azin dyes

Category:Eurhodin dyes Category:Safranin dyes, derivates of safranin Indamins

Category:Indophenol dyes, derivates of indophenol

Category:Oxazin dyes, derivates of oxazin

Oxazone dyes, derivates of oxazone Category:Thiazin dyes, derivatives of thiazin

Category:Thiazole dyes, derivatives of thiazole Xanthene dyes, derived from xanthene

Fluorene dyes, derivatives of fluorene

Pyronin dyes

Category:Fluorone dyes, based on fluorone

Category:Rhodamine dyes, derivatives of rhodamine AZO DYE

Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more stable derivatives contain two aryl groups. The N=N group is called an azo group.

As dyes and pigments

A Yellow Azo Dye

As a consequence of -delocalization, aryl azo compounds have vivid colors, especially reds, oranges, and yellows. Therefore, they are used as dyes, and are commonly known as azo dyes, an example of which is Disperse Orange 1. Some azo compounds, e.g., methyl orange, are used as acid-base indicators due to the different colors of their acid and salt forms. Most DVD-R/+R and some CD-R discs use blue azo dye as the recording layer. The development of azo dyes was an important step in the development of the chemical industry.

Azo pigments are colorless particles (typically earths or clays), which have been colored using an azo compound. Azo pigments are important in a variety of paints including artist's paints. They have excellent coloring properties, again mainly in the yellow to red range, as well as lightfastness. The lightfastness depends not only on the properties of the organic azo compound, but also on the way they have been absorbed on the pigment carrier. Many azo pigments are non-toxic, although some, such as dinitroaniline orange, ortho-nitroaniline orange, or pigment orange 1, 2, and 5 have been found to be mutagenic. Some Azo Dye Compounds and their structures REQUIREMENTSThe items listed below are required for the preparation of various dyes

Beaker

Test tubes

Spatula

Weight box

Burner

Conical flask

Measuring cylinder

Physical/Digital balance

Pair of gloves, lab coat, etc.

Para Red Dye

IUPAC name :- 1-[(E)-(4-Nitrophenyl)diazenyl]-2-naphthol

Other names :- 1-[(4-Nitrophenyl)azo]-2-naphthalenol, 1-((4-nitrophenyl)azo)-2-naphthol, 1-[(p-nitrophenyl)azo]-2-naphthalenol, 1-[(p-nitrophenyl)azo]-2-naphthol, paranitraniline red, Pigment Red 1, C.I. 12070, Recolite Para Red B, Carnelio Para Red BS

Identifiers

CAS number6410-10-2

ChemSpider13544963

EC number229-093-8

Properties

Molecular formulaC16H11N3O3

AppearanceRed solid

Melting point248 - 252 C

Hazards

R-phrasesR36/37/38

S-phrasesS26, S36

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.

Synthesis

Para Red is prepared by diazotisation of para-nitroaniline at ice-cold temperatures, followed by coupling with -naphthol.

PREPARATION OF PARA RED DYES

Procedure :-NaOH solution is prepared by dissolving 0.4g of NaOH flakes in 4mL of water.2g of NaOH and 0.g of -Naphthol were weighed.The solutions were prepared as follows:Solution A: 2g of Paranitro aniline,20mL of water and 8mL of conc.HCl.Solution B: 2g of NaNO2 and 20mL of water.Solution C: 0.2g of -Naphthol dissolved in 10%NaOH solution and was diluted with water (10mL)All the three solutions are kept in an ice bath for 30 min. Solution A was added to Solution C and then Solutions B was added to this solution slowly with constant stirring and then filtered and dried.Para Red was obtainedObservation- The filtrate after drying was deep red in colour. It gave needle shaped crystals on drying. FLUORESCENT DYE Resorcinol

Phthalic Anhydride

Sodium Hydroxide

Concentrated Sulphuric Acid - mL

Procedure :-

Take 2 g Resorcinol and 2 g of Phthalic anhydride and add 2 mL of Concentrated Sulphuric acid to it.

Heat the contents on a burner till the contents turn black.

Cool the contents and add to 20 mL of 5% Sodium hydroxide in a conical flask.

Vary concentration of Sodium hydroxide and water to obtain different intensities of colour.

Reactions

Observation of fluorescene :-

Prepare a solution of fluorescein by dissolving 5 milligrams (or spatula tip size) of the sample in 50 mL 0.1 M NaOH solution. Place the solution in a vial and place it on a black non-reflective surface, such as a lab bench. Place a bright light source (sunny window works well) on the opposite side of the bench from the observer and note the appearance of the solution. In this case, the color observed is primarily due to absorbance of some wavelengths of visible light passing through the sample from the light source.

Next observe the same solution at a position 90 degrees from the light source. The color observed from this perspective is primarily due to fluorescence.

Finally, in a darkened room shine a long wave UV lamp at the sample vial. The vials should visibly glow from the fluoresced light