EXPLAIN IN DETAIL. AND GIVE STEP BY STEP to earn full points! a. Assume that you

Question

EXPLAIN IN DETAIL. AND GIVE STEP BY STEP to earn full points!

a. Assume that you used isopentyl alcohol whose oxygen atom was labeled with O - 18 (instead of normal O - 16) in the esterification of acetic acid. Draw the structure of the product and show with a star (* ) where the O - 18 label would be located. (Hint: See the mechanism on p. 94)

b. What major band in the IR spectrum is definitive proof that the ester product formed?

c. Why must the organic phase be washed with sodium bicarbonate in the work - up procedure?

d . Why is an excess of acetic acid used in the synthesis of isopentyl acetate?

e. What are the benefits of a microwave synthesizer in organic chemistry?

Explanation / Answer

A

product is CH3C(=O)-O(18)-CH2-C(CH3)3   

B

the main one is the C=O from 1750 - 1735. If the peak is in this region then there is a ester.   

C

Precisely. The Fischer esterification is done typically with an acid catalyst. You can add some drops of sulfuric acid, or saturate the solution with HCl gas.

When you work it up, a wash with a bicarbonate solution will neutralize any mineral acids you may have added in the reaction, and also remove any unreacted acid as its sodium salt.

Your ester is extracted into the organic phase. Everything else is left behind in the aqueous phase.

D

Isopentyl acetate is prepared by the direct esterification of acetic acid with isopentyl alcohol. Since the equilibrium does not favor the formation of the ester, it must be shifted to the right, in favor of the product, by using an excess of one of the starting materials. Acetic acid is used in excess because it is less expensive than isopentyl alcohol and more easily removed from the reaction mixture.

In the isolation procedure, much of the excess acetic acid and the remaining isopentyl alcohol are removed by extraction with water. Any remaining acid is removed by extraction with aqueous sodium bicarbonate. The ester is purified by distillation.

E

Advantages of Microwaves for Organic Synthesis

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