Aim: To prepare Bartituric acid from urea dimethyl malonate.
Apparatus:
- RBF
- Beaker
- Measuring Cylinder
- Reflux condeser
- Water bath
- Funnel
- Heating mantel
Chemicals Required:
- Sodium metal
- Diethyl malonate
- Urea
- Sodium Hydroxide
- Ethanol
- Calcium chloride
- Conc HCL.
Reaction:
Mechanism:
Procedure:
Assemble a double surface reflux condenser with a 2litre round bottomed flask, place 11.5g(0.5mol) of clean sodium. Mix 250ml of absolute ethanol in a portion and if the reaction is undulvigorous, immerse the flask within ice. When all the sodium has completed reaction. add diethyl malonate 80g(76ml, 0.5mol), followed by a solution of dry urea 30g (0.5mol) in 250ml of hot(70°C) absolute ethanol. Shake the mixture thoroughly, attach a calcium chloride guard tube to the top of the condenser, start reflux of the mixture for 7hr in an oil bath and heat to 110C. A white solid will be separated. Treat the reaction with hot(50°C) water 450ml and then with conc HCl, with constant stirring, until the solution will be acid(about 45ml). Filter the resulting almost clear solution and leave it in the refrigerator overnight.Filter the solid at the pump, wash it with 25ml of cool water, drain well and then dry at 100°C for 4hours.
Calculation:
Here limiting reagent is diethyl malonate; hence yield should be calculated from its amount taken.
Molecular formula of diethyl malonate=C7H12O4
Molecular formula of barbituric acid= C4H4N2O3
Molecular weight of Diethyl malonate= 160g/mole
Molecular weight Of Barbituric acid=128g/mole
Theoretical yield:
160g diethyl malonate forms 128g barbituric acid
Therefore, 80g diethyl malonate will form(X)g barbituric acid
X=(128x80)/160 =64g
Theoretical yield=64g
Practical Yield = _____g
%yield = (Theoretical yield/Practical Yield)x100
Uses: Itself not active pharmacologically, but its derivatives are used as sleeping pills and sedatives.
Report: Barbituric acid was synthesized and the percentage yield was found to be ____%
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