Question

Explain the purpose of the following in the above experiment:

a. phosphoric acid

b. fractional distillation

c. sodium hydroxide

d. anhydrous sodium or magnesium sulfate

e. ice-cooled receiving flask

f. covering the flask with a watch glass in step 4

In this experiment, cyclohexanol will be dehydrated using a strong acid (concentrated phosphoric acid) to cyclohexene via an E1 MECHANISM.

Answer 1

a. Phosphoric acid acts as dehydrating agent, catalyzed the reaction and to remove water from cyclohexanol and will get cyclohexene.

b. Fractional distillation: Since reaction is reversible, cyclohexyl cation will be reacted with cyclohexanol to form dicyclohexyl ether, some water and again cyclohexanol therefore reqiured fractional distillation to separate byproduct also.

c.

Sodium hydroxide:

It is necessary to be remove traces amount of phosphoric acid from the crude product. sodium hydroxide reacts with traces amount of phosphoric acid to form sodium phosphate salt.

d. To remove water from crude product required anhydrous sodium of magnesium sulphate.

e. Ice-cooled receiving flask: because low B.P.of cyclohexene and dicylohexyl ether, maintained low temperature

f. Cover the solution of cyclohexene and ether and then again redistill it.