Chapter 21, Problem 21.56P

Interpretation Introduction

(a)

Interpretation: The stable carbonyl compound, ${\text{NO}}_{\text{2}}{\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{COCH}}_{\text{3}}$ (p-nitroacetophenone) or ${\text{CH}}_{\text{3}}{\text{OC}}_{\text{6}}{\text{H}}_{\text{4}}{\text{COCH}}_{\text{3}}$ (p-methoxyacetophenone) is to be identified.

Concept introduction: Electron withdrawing groups pulls electron density towards itself, and thus destabilizes the benzene ring, whereas electron releasing groups push electron density away from it, that is towards benzene ring, and thus stabilizes the benzene ring more.

Interpretation Introduction

(b)

Interpretation: The compound that forms higher percentage of hydrate at equilibrium is to be identefied.

Concept introduction: Aldehydes and ketones yield gem-diols at equilibrium, when they undergo addition reaction with ${\text{H}}_{\text{2}}\text{O}$. These gem-diols are called hydrates. The carbonyl carbon of aldehyde/ketone is stabilized by the electron donating groups placed near to it, whereas the carbonyl carbon of aldehyde/ketone is destabilized by the electron withdrawing groups placed near to it.

Interpretation Introduction

(c)

Interpretation: The compound that exhibits carbonyl absorption at higher wavenumber in its $\text{IR}$ spectrum is to be identified, and the reasoning of each part is to be explained.

Concept introduction: Electron releasing groups decreases the bond order of the $\text{C}=\text{O}$ bond that is decrease in double bond character, whereas the electron withdrawing groups increase the bond order of the $\text{C}=\text{O}$ bond.