Glacial Acetic Acid Lab Report

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Introduction: Benzopinacol can be prepared from benzophenone in presence of sun light
(photochemically) using isopropanol as the reducing agent in presence of acetic acid. Acetic acid is added to prevent the cleavage of benzopinacol to benzophenone and benzhydrol by the alkali derived from the glass container used for the reaction. Benzopinacol obtained in the first experiment is converted to benzopinacolone by heating under reflux (5 minutes) with glacial acetic acid containing trace amount of iodine dissolved in it. This reaction is known as pinacol- pinacolone rearrangement.
Step I: Preparation of benzopinacol from benzophenone : Coupling reaction
Reaction:

Procedure:
1. Take a mixture of 1.5 g of benzophenone , one drop of glacial acetic
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Diazotized Sulphanilic Acid
1. Dissolve 1.1 g of anhydrous sodium carbonate in 50 mL of water in a 100 mL conical flask.
2. Add 4 g of sulphanilic acid to the solution and heat it until it dissolves. A small amount of suspended material may render the solution cloudy.
3. Filter the hot solution and rinse the used filter paper with 2-5 mL hot water.
4. Cool the filtrate to room temperature, add 1.5 g of sodium nitrite, and stir until reaction is complete.
5. Pour this mixture, while stirring, into a beaker containing 25 mL of ice water to which 5 mL of concentrated hydrochloric acid have been added. The diazonium salt of sulfanilic acid should soon separate as a finely divided white precipitate. Keep this suspension cooled in an ice bath until it is to be used.
2. Methyl Orange
1. In a test tube, mix together 2.7 mL of dimethylaniline and 2.0 mL of glacial acetic acid.
2. Add this solution to the cooled suspension of diazotized sulhanilic acid in the beaker. Stir the mixture vigorously. In a few minutes, a red precipitate of helianthin should form. Keep the mixture cooled in an ice bath for about 15 minutes to ensure completion of the coupling
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Pour the hot reaction mixture now out into a petridish, covered with a paper to prevent loss by sublimation, and allow to cool.
Step II: Preparation of anthranilic acid from pthalimide
Reaction:
(Step 2 is Hoffmann degradation reaction)
Procedure:
4. Dissolve 15 g sodium hydroxide in 15 ml water. Keep the solution cool and add 4.2 mL bromine in one lot.
5. Shake the mixture till all the bromine has reacted. Maintain the temperature below 0 º C and finely add 12g powdered phtalimide in one lot.
6. Shake the mixture vigorously and add a cold solution of 11 g sodium hydroxide in 40 mL water.
7. Shake the reaction mixture and the temperature rises to about 70 0C . Warm the mixture to 80 0C for 5 minutes.
8. Cool the clear solution in ice bath and add conc. HCl slowly (about 30 ml) with stirring until the solution is just neutral.
9. Add 10-12 mL glacial acetic acid gradually, so as to precipitate the anthranilic acid . Filter the separated acid, wash with cold water and recrystallize it from hot water.
Mechanism:
Step III: Preparation of o-chlorobenzoic acid from anthranilic

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