CBSE 2026 · Region 2 · Set 1 · Q30 · 4 marks

Like $\displaystyle \mathrm{NH}_{3}$, nitrogen atom of amine is trivalent and carries an unshared pair of electrons. Nitrogen orbitals in amines are therefore $\displaystyle \mathrm{sp}^{3}$ hybridised and the geometry of amines is pyramidal. Lower aliphatic amines are soluble in water due to the formation of hydrogen bond with water molecules. The solubility decreases as the molar mass of amines increases due to increase in size of hydrophobic part. Higher amines are insoluble in water. However amines are less soluble in water than alcohols because of low electronegativity of nitrogen as compared to oxygen. Boiling points of isomeric amines follow the order $\displaystyle 1^{\circ}>2^{\circ}>3^{\circ}$. It is due to the fact the amines are held together due to hydrogen bonding. Extent of hydrogen bonding is more in primary amines than in secondary amines as two hydrogen atoms are available for hydrogen bond formation. Tertiary amines do not show hydrogen bonding because of the absence of hydrogen atom attached to nitrogen. Amines can be prepared from, nitro compounds, nitriles, amides etc.

(a)

Complete the following equations :

(a)

(ii)

(b)

Why primary amines have higher boiling points than tertiary amines?

(c)

Classify the following amines as primary, secondary or tertiary :

(ii)

(c) Out of Butan-$\displaystyle 1$-amine and Butan-$\displaystyle 1$-ol, which is more soluble in water?

CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.