To prepare and submit Coumalic acid from Malic acid.

Experiment

 Object:

To prepare and submit Coumalic acid from Malic acid.

Requirements:

Sulphuric acid, malic acid, methanol, round bottom flask, water bath.

Theory:

Coumalic acid is formed by self-condensation of malic acid in fuming sulphuric acid.

Reaction involved:

Procedure:

1.Add 180 ml of sulphuric acid to 202 g (1.5 mol) of finely powdered malic acid
contained in a 2 litre round-bottomed flask.

2.At intervals of 45 minutes, add three 50 ml portions of fuming sulphuric acid
(25 % SO3); a slight exothermic reaction sets in with the steady evolution of gas.

3.Swirl the mixture frequently to obviate excessive foaming, and when the evolution ofgas has slackened, heat the reaction mixture on a water bath for 2 hours.

4.Cool the mixture and pour on to 800 g of ice with stirring. Set the mixture aside in a
refrigerator for 24 hours and then filter the crude coumalic acid and wash with small
portions of ice water.

5.Recrystallize the crude product from methanol to give coumalic acid as light yellow
crystals, M.P. 206-208°C. The yield of product is 65 g (62%).

Observation/calculation:

Theoretical yield =_____mg
Practical yield =______mg

Percentage of yield = _____%

Result:

 The yield of obtained product was found to be ...... gm and percentage yield was

% and melting point was found to be ....... °C.

Uses.:

 It is an example of intermediate used in bulk drug industry.

Cautions:

1. Glass ware should be clean and dry before being used
2. Washing is essential to remove the mineral acid and to avoid partial esterification
that otherwise takes place during the methanol recrystallization step.