Chapter 23.3, Problem 18SSC

Interpretation Introduction

Interpretation:

The equation for the complete hydrogenation of linoleic acid should be determined.

Concept introduction:

The building blocks of fat in our bodies and in food are known as fatty acids. Fatty acid consists of carboxylic acid with long aliphatic chain which can be saturated or unsaturated.

Answer to Problem 18SSC

The complete equation for the complete hydrogenation of linoleic acid is:

${\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{4}}{\text{CH=CHCH}}_{\text{2}}{\text{CH=CH(CH}}_{\text{2}}{\text{)}}_{\text{7}}{\text{COOH+H}}_2\stackrel{\text{Ni}}{\to }{\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{4}}{\text{CH}}_2{\text{CH}}_2{\text{CH}}_{\text{2}}\text{CH}={\text{CH(CH}}_{\text{2}}{\text{)}}_{\text{7}}\text{COOH}$

Explanation of Solution

The chemical reaction between a molecule and molecular hydrogen in the presence of catalyst like nickel, palladium and platinum is known as hydrogenation reaction.

The formula of linoleic acid is ${\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{4}}{\text{CH=CHCH}}_{\text{2}}{\text{CH=CH(CH}}_{\text{2}}{\text{)}}_{\text{7}}\text{COOH}$.

The reaction of linoleic acid with ${\text{H}}_2$ is:

${\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{4}}{\text{CH=CHCH}}_{\text{2}}{\text{CH=CH(CH}}_{\text{2}}{\text{)}}_{\text{7}}{\text{COOH+H}}_2\stackrel{\text{Ni}}{\to }{\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{4}}{\text{CH}}_2{\text{CH}}_2{\text{CH}}_{\text{2}}\text{CH}={\text{CH(CH}}_{\text{2}}{\text{)}}_{\text{7}}\text{COOH}$

In the above reaction, two double bonds are present in linoleic acid; one double bond reduces to single bond with the addition of two hydrogen atoms in the presence of molecular hydrogen.