Physical Properties & Boiling Point / Solubility Trends

Boiling Point Order:

$$\text{Boiling Point Order: } 1^\circ \text{ Amine} > 2^\circ \text{ Amine} > 3^\circ \text{ Amine}$$

$$\text{Intermolecular H-Bond Strength: } \text{Alcohols } (\text{O--H}\cdots\text{O}) > \text{Amines } (\text{N--H}\cdots\text{N})$$

Concept: Primary ($$1^\circ$$) and secondary ($$2^\circ$$) amines form intermolecular hydrogen bonds due to the presence of $$\text{N--H}$$ bonds, whereas tertiary ($$3^\circ$$) amines have no hydrogen atom attached to nitrogen and cannot form self-intermolecular H-bonds.

Solubility Trend:

• $$\text{Solubility in Water: } 1^\circ > 2^\circ > 3^\circ$$ Decreases with increasing molar mass / hydrophobic alkyl chain length