To PREPARE THE BENZOIC ACID BY THE OXIDATION OF BENZALDEHYDE AND DETERMINE IT'S MELTING POINT

 Apparatus Required 

• RB flask

• Condenser 

• measuring cylinder

• test tubes and holders

• Thiele's tube

•  beaker

• funnel

• filterpaper

Chemical Required

• Benzaldehyde = (5ml)

• Anhydrous Sodium Nitrite = (3gm)

• Potassium permangnate = (4gm)

THEORY

Benzoic acid is a nuclear aromatic carboxylic acid in which one- COOH group is directly attached to nuclear or carbon of benzene ring Benzoic acid is prepared by the oxidation of benzaldehyde with the help of KMno4 in presence of alkali

PROCEDURE:

we mixed 5ml benzaldehyde, 3gm NaNo2 4gm kMno4 and 100 ml of distilled water in round bottom flask fitted with an air condenser or heated the mixture gently for about 45-50 minutes. untill all oily drops of benzaldehyde dissappeared and Mno₂ & (black ppt) was precipitated out we allowed it cool and filtered. Acidified the filtrate with conc. H2so4, when white creamy precipitate of benzoic acid was obtained It was, then filtered and washed with sold distilled water. filter paper was separated from funnel and residue was poured in a beaker containing some water added charcoal (to decloris) and stirred well. finally, we collected the pure Crystals by suction filtration, which was wash with little cold water and dried it been fold of filterpaper by pressing. We put some pinch benzoic acid in capillary tube which was fitted in Thiele's tube and it's melting point I was determined.

RESULT

• Appearance: White shining crystals.

• Yield: 3.1g

• observed Melting point: 120°c

• Actual Metting point: 1201°c

CONCLUSION

Hence, benzoic acid can be prepeared by
the oxidation of benzaldehyde and melting
point · be determined.