Lab Report Marco Huerta
Partner: Sami Mrestani Chem 12B – Organic Chemistry
Objective: To prepare a local anesthetic, Benzocaine, by the direct estherification of p-aminobenzoic acid with ethanol.
Abstract: Over the years many new local anesthetics have been synthesized and tested. Though many have not come into general use, the search for the perfect local anesthetic is still under way. An interesting fact about these compounds is that they all share common feature (see ...view middle of the document...
It is also a possible sulfonamide antagonist.
p-Aminobenzoic acid ethanol Benzocaine
Since the reaction is in equilibrium, excess water would cause the reaction to favor the reactants and thus not produce the desired product. Our intent is to create the ethyl esther functional group.
Results: Benzocaine Product
Mass .0705g .0411g
M.P. 86.55-88oC 89.5-90.9oC
Melting Point % error
Crude = 90o-88o/90 x 100 = 2.2% error
Purified = 90.9o-90o/90 x 100 = 1.0% error
0.131g p-aminobenzoic acid x 1mol/137.14g = 9.55x10-4 mol p-aminobenzoic acid *
1.20 mL ethanol x .789g/mL x 1mol/46.07g = 2.055x10-2 mol ethanol *-limiting reagent
9.55x10-4 mol p-aminobenzoic acid x 1mol/1mol x 165.19g/1mol = .1578g Benzocaine
.0411g*/.1578g Benzocaine x 100 = 26.05 %* Recrystallized Benzocaine
.0705-.0411/.0705 x 100 = 41.7 % loss due to recrystallization*
*= reported values are much lower than actual yields because m.p. and IR analysis were done prior to weighing final product
Major IR peaks
NH2 peaks = ~ 3300-3400cm-1
Strong Aromatic C-H bonds = ~ 3000cm-1
Strong Carbonyl signal = ~ 1700cm-1
1. What is the structure of the precipitate that forms after the sulfuric acid has been added?
2. When 10% sodium carbonate solution is added, a gas evolves. What is the gas? Give a balanced equation for this reaction.
* Carbon dioxide
* 2 NH3 + Ph-CO2Et + CO3-2 -- 2 H2N-Ph-CO2Et + H2O + CO2
3. Explain why benzocaine precipitates during the neutralization.
* During neutralization the acidic proton is removed making the benzocaine insoluble in the solvent we used to dissolved...