CHE 334 EXP 3 laboratory PDF

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CHE 334 EXPERIMENT NO:

3

EXPERIMENT TITLE: DIAZOTIZATION PREPARATION OF PHENYL AZO-BNAPHTHOL FROM ANILINE SURNAME:

BOK

NAME:

MOEMEDI

ID NO:

201300337

DATE:

10 FEBRUARY 2016

DAY:

WEDNESDAY

AIM: Synthesis of phenyl azo-β-naphthol from aniline, calculation of percentage yield and determination of its melting point. ABSTRACT 1-phenylazo-2-naphthol or known as “Sudan-1” was synthesized by diazotization and coupling reactions. Diazonium salts are formed in the diazotization reaction while in the coupling reaction coupling products are formed because the positively charged aryl diazonium ion becomes electrophilic towards highly activated substrates. Aniline and β-naphthol was made to react and recrystallization was done to obtain a product with 2.43g and the theoretical yield of 3.40 g was calculated. The percentage yield of 71.5% was found. While the theoretical melting point is 131oC (Williamson, 1994) and the obtained melting point was found to be in range 128 – 130 °C.

INTRODUCTION Azo compounds are compounds containing a diazene molecule where hydrogen is replaced by R. The general formula for an azo compound is R-N=N-R' where R and R’ can be an aryl or an alkyl group. Aryl azo compounds have vivid colors ranging from red to yellows. Because of this trait, azo compounds are usually used as dyes and are commonly known as azo dyes. Dyes are colored because of delocalization. The extended -N=N- bond causes light to be absorbed in the visible regions. The groups responsible for the delocalization and absorption of light are called chromophore(Williamson, 1994). Most dyes also contain auxochromes like carboxylic acid, sulfonic acid, amino, and hydroxyl group which influence dye solubility and can shift the color of the dye. Dyes can be used as acid-base indicators, food coloring, biological staining agent, and textile dyes. The dyes are colored because light is absorbed in the visible region. Azo dyes are very easy to synthesize.

REAGENTS:      

Aniline Hydrochloric acid Sodium nitrite β-naphthol Sodium hydroxide 95% ethanol

EXPERIMENTAL PROCEDURE 1.25 ml of aniline was dissolved in a mixture of 4 ml of hydrochloric acid and 5 ml of water and the solution was cooled in ice of temperature between 0 and 5 °C and the solution of 1 g sodium nitrite in 3-4 ml water was added to the solution in ice with continuous shaking and temperature controlled

below 5 °C. In another flask 2 g of β-naphthol was dissolved in a solution of 1.25 g sodium hydroxide in 13 ml of water and the solution was heated to get the clear solution. The solution was then cooled in ice bath to 0 - 5°C. After both solution attained the temperature of the ice bath, one solution was added drop wise to the other with continuous stirring for 30 minutes without allowing temperature to rise above 10°C. Suction filtration was performed to obtain solid that was washed with cold water. The solid was dried and recrystallized from 95% ethanol. RESULTS AND ANALYSIS Table : showing amount of product obtained Description Mass of petri dish + filter paper Mass of petri dish + filter paper + product Mass of product

Mass (g) 45.91 48.34 2.43

Melting point of phenyl azo-β-naphthol: 128 - 130°C Calculation of percentage yield Volume of aniline = 1.25 ml Density of aniline = 1.02 g/ml Molar mass of aniline = 93.13 g/mol Mass of aniline = density x volume = 1.02g/ml x 1.25 ml = 1.275 g Moles of aniline = mass/molar mass = 1.275g/93.13g/mol = 0.01369 mol C6H5NH2 1 0.01369

: C16H12ON2 :

1

:

x

x = 0.01369 mol of C16H12ON2

Molar mass of C16H12ON2 = 248.28 g/mol Theoretical mass = moles x molar mass

= 0.01369 mol x 248.28 g/mol = 3.40 g Percentage yield = actual yield/theoretical yield x 100 = 2.43g/3.40 x 100 = 71.5 % DISCUSSION The product was recrystallized from ethanol. The best IR spectrum of the product was determined when the product was dry. The IR spectrum of the product display a strong N=N absorption band at 1386.2 cm-1. The OH bending vibration appeared in the region of 1495.1 – 1448 cm-1, C-H stretching vibration appeared in the region of 1203.7 – 747.52 cm-1 and C=C stretching vibration band appeared in the region of 1615.8 - 1551 cm–1.The product obtained was enough which shows that the method used was suitable for the preparation. 1)The diazonium coupling reaction is an electrophilic aromatic substitution reaction (Kirner, 2007)

2) Synthesis of orange II from benzene and β-naphthol

Sulfanilic acid will be diazotized and used the resulting diazonium ions will be reacted with ßnaphthol to form the azo dye Orange II. The sulfanilic acid will be made soluble by neutralization with sodium carbonate solution. 3) The hydroxyl group is assigned 6.88 ppm,16.26ppm is assigned to benzene.

4) IR spectrum: 1616 cm-1 → C=C 16.26 cm-1 → C-H

CONCLUSION The light orange crystals of 1-phenyl-azo-2-naphthol of 2.43 g were obtained. The percentage yield was calculated and found to be 71.5%. The melting point was determined to be in the range 128-130 °C and the literature value for melting point was 131°C(Clarke,2007) . The IR spectrum of the product was determined.

REFERENCES 1) K. L. Williamson, Macroscale and Microscale Organic Experiments, 2nd Ed. 1994, Houghton Mifflin, Boston Revised 6/28/07 2) H. T. Clarke and W. R. Kirner. "Methyl red". Org. Synth.; Coll. Vol. 1, p. 374...