Chapter 15, Problem 15.119P

(a)

Interpretation Introduction

Interpretation:

The structures A, B and C has to be matched with the correct vitamin A compound: retinal (an aldehyde), retinol (an alcohol) and retinoic acid (a carboxylic acid).

Concept Introduction:

An aldehyde compound contains the functional group $\text{-}\stackrel{\stackrel{\text{O}}{\text{||}}}{\text{C}}\text{-H}$ at the end of the carbon chain.

An alcohol group contains functional group $\text{-OH}$ attached to the carbon atom either at the end of the chain or in the middle.

A carboxylic acid contains the functional group $\text{-}\stackrel{\stackrel{\text{O}}{\text{||}}}{\text{C}}\text{-OH}$ at the end of the carbon chain.

(b)

Interpretation Introduction

Interpretation:

Retinal can be converted to retinol and retinoic acid.  The reactions has to be identified as oxidation reaction and reduction reaction.

Concept Introduction:

Oxidation reaction:

The addition of oxygen atoms or the removal of hydrogens from the reactant in the formation of product is said to be oxidation.

Reduction:

The addition of hydrogens or the removal of oxygen atoms from the reactant in the formation of product is said to be reduction.

(c)

Interpretation Introduction

Interpretation:

The given structure is of beta-carotene found in carrots.

The reason has to be suggested for the importance of beta-carotene in the vision process.