Aim: To prepare and submit 1-Phenyl Azo-2-Napthol from aniline and report its melting point.
Requirements:
a) Chemical Required: Aniline, Sodium nitrite, HCl, NaOH, β-Napthol, Ethanol,(re-crystallization).
b) Apparatus: Conical flask, Measuring Cylinder, Water bath, Glass rod, Funnel, Thermometer.
Principle:
Primary aromatic amines dissolved in aqueous mineral acids (HCl) and sodium nitrate (NaNO3) at temperature of about 0-5° C to from diazonium salts. This type of reaction is known as Diazotization.
Diazonium salt reacts with aromatic compound having activating group at ortho-para position form AZO compounds. This reacion is called coupling reaction.
In this reaction aniline is first dissolved in dil HCl and sodium nitrite (NaNO3) to form benzene diazonium chloride, this then reacts with β-Napthol to form 1-Phenyl Azo-2-Napthol.
Procedure:
- In a beaker dissolve 1.3ml of Aniline and 5ml of conc. HCl. Dilute with 15ml of cold water. Cool the beaker in an ice bath until the temperature falls below 0-10°C
- Dissolve 1.5g of sodium nitrate solution and cool. Slowly add to the Aniline solution by stirring.
- Dissolve 3g of powdered β-Napthol in15ml of 10% sodium hydroxide solution.
- Cool this pour the diazonium solution prepared earlier into the β-Napthol solution with constant stirring a bright red color solution is performed continuous stirring. Cool the beaker in an ice bath until the temperature falls below 0-10°C.
- Keep it aside for 10 mins, filter the precipitate and wash with water.
Reactions:
Calculation:
Molecular weight of Aniline =93g
Molecular weight of 1-Phenyl Azo-2-Napthol =248g
93g of Aniline-248g 1-Phenyl Azo-2-Napthol
1.3g of Aniline should yield = 1.3x248/93 = g
Theoretical Yield= 3.46g
Practical Yield= Xg
Percentage Yield= (Practical yield/Theoretical yield)x100
Result:
The Percentage yield of 1-Phenyl Azo-2-Napthol was found to be - ______
Melting point of 1-Phenyl Azo-2-Napthol is 131°C
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