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Org-Chem 221 Lab

Exp
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Ghassan Daghrah

Student Name: Yazan Abu Kweder Partner Name: Aseel Mhani
Student No: 1140426

Partner No: -------------------------

Experiment No: #8
Experiment title: Local Anesthetics – The Synthesis of Benzocaine

Submission date: 23/4/2016

Objectives:
1- To learn the technique of benzocaine synthesis by esterfication
reaction ( Fischer Esterfication Reaction)
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3- To Determine the melting point of the benzocaine
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pbworks
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scribd
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50g (0
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Then swirl the
of the reaction
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2- Add to the above mixture
5ml of concentrated sulfuric
acid (H3PO4) dropwise
with a Pasteur pipette to the
ethanol-aminobenzoic
solution , then you will see
the solid precipitate out of
the solution
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4- If any precipitate remains
after heating , cool the
solution at room
temperature for 203
minutes , then add 3 ml of
absolute ethanol and 0
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5- Resume heating under
gentle reflux until all the
solids dissolve
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7- Remove the condenser and
pour the hot solution into a
beaker contains 100 ml of
cold water
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9- Precipitate the crude
benzocaine
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 It is very important
that all of the solid
dissolve during this
period , to get the
maximum yield
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 Do not add additional
sodium carbonate
(excess) because it will
not produce further
evolution of CO2 Gas
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11Re-Crystallize the
product from water and
95% ethanol using the
mixed solvent technique
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Data:
Fill in the chart below with appropriate structures, and physical properties of reagents
needed to complete the reaction
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Experimental results are to be filled in during completion of the
experiment
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52g
Volume of Suluric acid (H2SO4) = 5ml
Volume of Absolute ethanol = 25ml
Weight of filter paper =
Weight of Benzocaine (Experimental yield) = 1
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189 g/mol
Density of Benzocaine = 1
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14 g/cm3
Ethanol Density = 0
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06844 g/mol
Filter Paper :A- Company : Double Rings
B- 102 Qualitative
C- Medium filter speed (20-30um)
D- Ash content 0
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50/137
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018 moles
Ethanol #moles = (Volume *density)/ Molecular weight
= (25ml * 0
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06844
= 0
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So the limiting reagent is p-aminobenzoic acid !!!
So the theoretical benzocaine #moles = 0
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018 * 165
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973 grams
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89/2
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57%

Discussion & Comments:
Provide a summary of the experiment including observations, analysis of all data and
results, and methods to correct errors or optimize the experiment
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Although the alchohol ,which is absolute ethanol was added in excess
to drivethe forward reaction , methodologies limit the extent that the ester can
be produced
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89 grams
,whereas the mass of the ester should have theoretically been 2
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57%
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Although sulfuric acid
is necessary to start the reaction , the acid catalyst is capable of driving the
reaction in both forward and reverse reactions, with a reverse reaction still
occurring , the yield could never be 100%
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Finally , The melting point range of benzocaine was (90-91) °C , which is so
close to the theoretical melting point which is 89-90 °C
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Questions:

Q2
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Q3
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In addition of Hydrochloric acid (HCl) which contains water , which will react
with ester which will shift the equilibrium to the left (Reactants) ,so it will cause
the lost (Lower yield) of the product
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The ester will react with the cold water ,so the equilibrium of the reaction will
shift to the left as a result of Le Chaterilier's Principle , so the product will be
lost ( Lower yield of product ) which is benzocaine
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However , when the solution is made alkaline , the two
substances are easily separated , since p-aminobenzoic acid remains in solution
as the water soluble anion of the acid , whereas the benzocaine precipitates and
may be isolated by suction filtration
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Reference :- The Word of organic chemistry , A laboratory
Approach , David C
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