Aldehydes, Ketones and Carboxylic Acids - Physical and chemical properties

The Carbonyl group ($>C=O$) is polar due to the higher electronegativity of oxygen compared to carbon, making the carbon atom electrophilic and the oxygen atom nucleophilic.

Aldehydes and ketones have higher boiling points than non-polar hydrocarbons of similar molecular mass due to dipole-dipole interactions, but lower than alcohols because they cannot form intermolecular hydrogen bonds.

Lower aldehydes and ketones are soluble in water because they can form hydrogen bonds with $H_2O$ molecules.

Nucleophilic addition reactions are characteristic of carbonyl compounds. Aldehydes are generally more reactive than ketones due to steric and inductive effects.

Oxidation: Aldehydes are easily oxidized to carboxylic acids using mild agents like Tollens' reagent ($[Ag(NH_3)_2]^{+}$) or Fehling's solution ($Cu^{2+}$ ions). Ketones require vigorous conditions.

Reduction: Carbonyls can be reduced to hydrocarbons via Clemmensen reduction (using $Zn-Hg/HCl$) or Wolff-Kishner reduction (using $NH_2NH_2/KOH$).

$\\alpha$-Hydrogen reactions: Aldehydes/Ketones with at least one $\\alpha$-hydrogen undergo Aldol condensation in the presence of dilute alkali.

Cannizzaro reaction: Aldehydes with no $\\alpha$-hydrogen (e.g., $HCHO$, $C_6H_5CHO$) undergo self-oxidation and reduction (disproportionation) with concentrated alkali.

Carboxylic acids are more acidic than alcohols and phenols because the carboxylate ion ($RCOO^-$) is stabilized by two equivalent resonance structures.

Hell-Volhard-Zelinsky (HVZ) reaction: Carboxylic acids with $\\alpha$-hydrogen react with $Cl_2$ or $Br_2$ in the presence of red phosphorus to give $\\alpha$-halo carboxylic acids.