this is about Fisher esterification reaction of benzoic acid and methanol to for
ID: 1031936 • Letter: T
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this is about Fisher esterification reaction of benzoic acid and methanol to form methyl benzoate
9. Evaporate the ether by blowing l 10. Once all of the ether has been removed, find the mass of the prodd 11. Transfer about 1-2 mL of the product a liquid, you will be able to tell that the ether is gUIl percent yield to a clean and dry scintillation vial and cap it. This ple. Transfer the rest to a clean and dry scintillation vial and cap it. This will be your IR sample. WASTE DISPOSAL: Aqueous waste should be disposed into an "Aqueous Waste" bottle. Stopping point for Day One Post-lab Questions for Esterification: Why is the alcohol used in excess? Would the reaction work if the carboxylic acid were used in excess instead? 2 What would the major product be of the reaction below? H2SO4, 1 equivalent MeoH EtoH Would the reaction below give the desired ester? Why or why not? OOEt OEt 4. If acid were not added, what would be the product of the reaction you did? DAYS TWO AND THREE Your TA will tl you which day you will do IR and which day you will do NMR.Explanation / Answer
1. For the Fischer esterification of benzoic acid to methyl benzoate, the mechanism invovlesthe formation of an activated complex where the carboxylic acid is involved and that is the rate-limiting step. In that step, to avoid self-quenching of the activated complex by other carboxylic acid molecules, excess alcohol is used. Also irrespective of whether the carboxylic acid is used in excess or the alcohol, the reaction will work however if the carboxylic acid is used in excess, the product formed will not be in large, isolable quantities.
2. As explained above, the alcohol present in excess has more probability of attacking the carboxylic acid after its activation thus forming an ester. In this case, while MeOH is used stoichiometrically with EtOH taken in excess as the solvent, the ester formed will most likely be ethyl cyclopentanoate along with a small quantity of methyl cyclopentanoate.
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