Question

Consider the below reaction where 6.1 g of benzoic acid is used to get 7.8 g of m-bromobenzoic acid.

The percentage yield of the product is ______
(Round off to the nearest integer)
(Given: Atomic mass: C:12.0 u, H:1.0 u, O:16 u, Br: 80 u)

Answer 1

Hint: Percentage yield describes the ratio of the percentage of actual yield to the yield that is calculated theoretically. If the values of theoretical and actual yield are the same, then we get a percent yield of 100%.


Formula used:
The formula to find out percentage yield is,
% yield\[{\rm{ = }}\dfrac{{{\rm{Actual}}\,{\rm{weight}}}}{{{\rm{Theoretical}}\,{\rm{weight}}}}{\rm{ \times 100}}\]

Complete Step by Step Solution:
The reaction of ketone with HBr in excess results in the breaking of the bond. The reaction is as follows:

Image: reaction of ketone with HBr
As the HBr is in excess, so, the bromination at the o and p position takes place.
The next step is the reaction of A with alcoholic potassium hydroxide in presence of acid. The reaction of an alkyl halide in alcoholic potassium hydroxide results in the removal of halogen acid to form an alkene.
So, the reaction is,

Image: reaction of A with alcoholic potassium hydroxide in presence of acid

The next step is the reaction of B with Ozone in the presence of acid.

Image: reaction of B with Ozone in presence of acid
This is an ozonolysis reaction. Ozonolysis is a reaction in organic chemistry where the breaking of double or triple bonds of alkynes, alkenes or azo compounds takes place in reaction with ozone. Alkynes and alkenes form organic compounds where the replacement of multiple carbon-carbon bonds takes place by a carbonyl group whereas azo compounds give nitrosamines.

Hence, the product C is in option C.

Note: The higher value of percent yield indicates that there is contamination of the product by excess reactant, water or another substance. A lower value of percent yield signifies that there is mismeasurement of the reactant or there is spilling of a portion of the product.