Title:

Synthesis of Benzocaine from P-Aminobenzoic acid

Apparatus:

Ø  Quick fit round bottom flask,

Ø  Condenser,

Ø  Water Bath,

Ø  Beaker,

Ø  PH Meter

Chemicals:

Ø  Amino Benzoic acid

Ø  Conc. H₂SO₄

Ø  Ethanol

Ø  Distilled water

Ø  10% Na₂CO₃ Soln.

Procedure:

First of all we will take round bottom flask and add in it 1.2g Para amino benzoic acid with 12ml ethanol and shake the flask so that all the solid dissolve in ethanol. Then we will add 1ml Conc. H₂SO₄ in it. After that we will attach the round bottom flask with condenser and reflux this reaction mixture at 80^oC up to one hour. In the next step we will separate the flask from condenser and transfer this material into the beaker and add 30ml distilled water in that beaker and allow this beaker to cool down. Then we will add 10% NaCO₃ in it to maintain the PH of this solution mixture upto8 or 8.5 after that we will wash the filtrate ppt with distilled water and in this last recrystallize it with ethanol.

Chemical Equation:

P-Aminobenzoic acid                                                Benzocaine

Mechanism:

Observation and calculations:   

Find Percentage Yield:

Molar mass of P-amino benzoic acid    = 137.14 g/mol

Molar mass of Ethanol is = 98.08

Mass of HNO₃ = d= m/v       d= 0.79

m=0.79 X 12 = 9.48g

No of moles of Ethanol used = mass/ molar mass

                                              = 9.48/98.08

                                              = 0.09665 g/mol     

No of moles of Paraamino benzoic acid used = mass/ molar mass

                                                =1.2/ 137.14

                                                = 0.008750 g/mol     

Because there is more No. of moles of ethanol than P-aminobenzoic acid, P-aminobenzoic acid is used up first as the reaction proceeds. We can conclude that ethanol is in excess and P-amino benzoic acid is the limiting reactant.

Theoretical yield:

Theoretical yield = No. of moles of P-aminobenzoic acid X molar mass of P-aminobenzoic acid

                         Theoretical yield = 0.0087 X 137

                          Theoretical yield = 1.1919g

                          Actual yield which we obtained was 0.79g

% Yield:

% Yield = Actual yield / Theoretical yield X 100

                                       % yield =  0.79g / 1.1919g X 100

                                       % yield =  66%

Results:

Mass of obtained benzil = 0.94g

The M.P of the product which we measured is ----^oC

The percentage Yield was = 66%

The Rf value is     2/3=0.67

Discussion:

The product which we prepared in laboratory was Benzocaine from P-Aminobenzoic acid                                          The percentage yield which we obtained of this product was 66% which is satisfactory since the yield may also be reduce due to climate change and it is also possible that there were different impurities present in a resulting product.