Question

The melting point of unsaturated fatty acids

• A. Increases with increase in double bonds
• B. Decreases with increase in double bonds
• C. Rises in some and falls in others
• D. There is no relationship between unsaturation and melting point

Answer 1

Answer: (B)

Decreases with increase in double bonds

Unsaturated fats are liquid at room temperature as they have double bonds. Saturated fatty acids have the single bond and are solid at room temperature. Hydrogenation is the process which involves the addition of hydrogen in the presence of nickel, palladium or platinum. On addition of hydrogen, the double bonds of fatty acids are reduced.

The unsaturated fats have the low melting point as they the double bond has the cis configuration which causes weak intermolecular interactions. With the increase in the double bond, the intermolecular interaction gets weak and the melting point decreases.

So, the correct answer is option B.