Question

1) Write a Reaction equation using 4- aminobenzenesulfulfonic acid (aniline derivative) and 8-anilino-1-naphthalenesulfonic acid (coupling agent). Write the mechanism.

SYNTHESIS OF AZO DYES INTRODUCTION Humans' love of color dates back almost to prehistoric times, yet it is not actually until the modern era that the full range of the rainbow has been accessible to the majority of people irn their clothes and other textiles. Ancient or medieval times have often been described as being quite splendid with their "tyrian purple" and "medieval scarlet", but closer examination shows that some of these colors were quite dull by today's standards EARLY HISTORY The history of dyeing can be divided into two great periods, the" and the "post-aniline" period. The former was characterized by a rather limited range of colors that were based on dyc-producing animals and plants. The main vegetable dyes available were extracted from madder root (Asia and Europe), producing a brilliant red and leaves of the indigo plant (India), yielding the blue dye still used today in jeans. Among the most important animal pre-aniline," extending to 1856 based dyes is the famous and expensive "Tyrian Purple" which was obtained from the small shellfish murez. We have the ancients' word that this dye was unbelievably beautiful, but evidence taken from ancient samples prove that it ranges through a rather uninspiring series of reds and purples. After seeing it, we wish that Homer had written about some of today's inexpensive coal-tar purples and reds. A far more beautiful natural color was introduced to Europe from Mexico in 1518, the brilliant scarlet dye cochineal, which had been produced from tiny lice which infest certain types of cactus. MODERN HISTORY Aniline (C&HsNH2) became available from coal tar in the 19h century and in1856, William Henry Perkin at the age of 17 used it in the synthesis of Mauveine (a mixture of 4 compounds- one of which is shown below). The era of synthetic dyes was born. H2N NH Structure of Mauveine A Soon thereafter, the main component of the dye in the madder root, Alizarin, was isolated by Carl Graebe and Carl Liebermann; prepared in the lab and the process was commercialized. Starting in 1865, recognizing the potential of synthetic dyes, Adolph von Baeyer researched the synthesis of indigo and determined its structure and first synthesized it in 1870. Structure of Indigo In 1897 the large scale industrial synthesis of indigo started and rapidly reached 10,000 tons a year, completely replacing the agricultural production. THE CHEMISTRY OF COLOR Colored substances absorb radiation in the visible region of the spectrum. The energy absorbed causes changes in electronic energy. Electrons are promoted from a ground state to an excited state. The electrons excited in this case are the outer bonding electrons or lone pairs. Not all electronic transitions are brought about by visible light as some require ultra-violet radiation. Those which absorb UV radiation appear colourless (unless they fluoresce). The energy needed to excite an electron in a coloured compound and in a colourless compound is shown below excitation energy excited state corresponds to visible radiation colorless ground state compound colored compound Colored Organic Compounds A dye molecule is built up from a group of atoms called a chromophore, which is largely responsible for its color. chromophores contain unsaturated groups such as C-O and-N=N-, which are often part of an extended delocalised electron system involving arene rings. Chrysoidine is a basic dye shown below: NH2 Chromophore H2N tached to the chromophore are two NH2 groups which interact with the chromophore to produce the orange color. Other functional groups may be added which can: . modify or enhance the colour of the dye make the dye more soluble in water . attach the dye molecule to the fibres of the cloth. All azo dyes contain the R-N-N-R' arrangement. How do dyes stick to fibres? This depends on the dye and the fibre to which the dye is attached. Protein-based fibres such as wool and silk have free ionisable CO2H and NH2 groups on the protein chains which can form an electrostatic attraction to parts of the dye molecule. For example the sulfonate group, SOs, on a dye molecule can interact with a NHs group on the protein chain. Cotton is a polymer with a string of glucose units joined together. Indigo which is used to dye denim jeans is a vat dye. Indigo is insoluble in water. The reduced form of indigo is soluble. Cotton is soaked in a colorless solution of the reduced form. This is then oxidized to the blue form of Indigo which precipitates in the fibers. он Cotton Wool OH OH Nylon Acetate Rayon Orlon N Dacron Figure 1: Structures of some fabric molecules SYNTHESIS Today's experiments deal with a class of compounds called Azo dyes, compounds that nected by a N-N double bond. You may have encountered as they are typical pH indicators. Methyl yellow, methyl orange, are some of the examples. They are straightforward to contain two aromatic fragments con these in chemistry experiments methyl red, congo red and alizarin yellow make and are of industrial importance. Azo dyes are prepared in a two step reaction, the first being the synthesis of an aromatic nium ion from an aniline derivative. The next step is coupling of the diazonium salt with an diazo aromatic compound (see below). The colors of azo dyes include different shades of yellow, red, orange, brown, and blue. Step 1: Diazotization NCI но Diazonium salt Step 2: Coupling reaction OH or NHPh NCI OH or NHPh Diazonium sat Aro dye Note: x.sosorNO2 so,NH4 Figure 2: Generalized synthesis of azo dyes You will work in pairs for this experiment. Each pair will be assigned a starting aniline derivative and a coupling agent. After synthesizing and recovering your azo dye, you will test your azo dye product as a direct dye to color a number of different fabrics (on a fabric strip). The possible aniline derivatives (with codes) are as follows: AM-1:3- Aminobenzenesulfonic acid AM-2: 4- Aminobenzenesulfonic acid 113.2 The possible coupling agents (with codes) are as follows: CA-1: 2-naphthol CA-2: 8-anilino-1-naphthalenesulfonic acid The stoichiometry (a 1:1 mole ratio) must be kept the same during the synthesis. SAFETY Personal protective equipment including safety goggles, gloves and a lab coat must be worm at all times during the experiment. Long pants should be worn along with close-toed shoes. No food or drink is allowed in the lab. Always work in the fumehood. Be careful when handling the products, they are deeply colored and will stain your skin and cloth for a long period of time. not wipe gloves on lab coats. PROCEDURE 1. In test tube A, add approximately 0.5 mL of conc. HCI and place in an ice water bath. 2tbe B, place .mmol436anuline or assigaed aniine derivattve, O u949 o.1349 0.13 g of sodium carbonate (Na COs), and S ml. of water and place in a hot water bath until a clear solution is obtained. S.omL 3. In test tube C, prepare a so water. อ . 2033 Remove test tube B from the hot water bath and pour the contents all at once from test 4. tube C into test tube B. 5. Add the contents from test tube B to test tube A and place in an ice water bath until a significant amount of solid has precipitated. 6. In a25 mL RBF (RBF-round bottonn flask), add 2.6 mmol-D-773 assigned coupling agent, 2 ml of 2.SM NaOH and a magnetic stir bar and place in an О.77 gofyour A ice-water bath. Turn on the stirrer and ensure the magnetic stir bar is working. cooling the reaction for 10 minutes. boiling commences (check with the instructor to ensure the set -up is correct) has dissolved. for 15 minutes. NaCI solution. filtrate using this fine grade paper. 7 Add the contents of test tube A to the RBF while stirring and continue stirring and 8. Remove the RBF from the ice water bath and heat the reaction using a thermowell until 9. Add I g of sodium chloride (NaC) to the flask and continue heating until all the NaCI gab 10. Stop stirring the reaction and cool to room temperature, then place in an ice water bath Noc 11. Filter the solid using vacuum filtration with a Buchner funnel and wash with a saturated 12. If no solid precipitates, ask your instructor for a piece of Grade 2 filter paper. Re-filter the Sand bath You will be given a rectangular piece of testing cloth which contains a number of strips of fabric. The figure below explains the order of the different fabrics starting from the top (with the serrated black border) with the first strip being acetate. Prepare the dye bath by mixing 50 mg of your dye with 20 mL of water in a 150 mL beaker. (note: if you did not obtain solid material place the pieces of filter paper that were used to collect the product in the beaker with the water). Heat the mixture on a hot plate to the boiling point. Once the mixture is boiling, stir it with a glass rod Immerse a piece of test fabric in the bath and use a piece of glass rod to keep it submerged for exactly 10 minutes. Add water as needed to maintain the volume of liquid in the bath. Using tweezers, remove the fabric from the dye bath and allow it to cool for 5 minutes. Then wash it thoroughly under cold running water. Pat the cloth dry with a paper towel. Write your name(s) and reactants on the back and attach this to your lab report Multifiber ribbon Acetate SEF Arnel(bright) Bleached cotton Creslan 61 Dacron 54 Dacron 64 Nylon 6,6 Orlon 75 Spun silk Polypropylene Viscose Wool References: Gung, B.W., Taylor, R.T.; 2004. J. Chem. Ed,81, 1630. Decelles, C.; 1949,J. Chem. Ed., 26, 583 Post lab questions: What conclusions can you draw about the relationship between chemical structure and dye color from the results of your experiment? 1. What conclusion can you draw about the relationship between the structure of the fabric molecule and the adherence ability of your dye? 2. Write a balanced equation for the preparation of the azo dye that you made. 3.

Answer 1

i have done according to azo dye hope your query will clear