GUJCET 2026 Chemistry Paper

Concept:In aqueous solution, the basic strength of substituted amines depends on the combined effect of the $+I$ effect, solvation (hydrogen bonding with water), and steric hindrance.Explanation:Ethyl groups are electron-releasing, so they increase electron density on nitrogen and raise basicity.However, this increase is limited by solvation and steric crowding.The secondary amine $(2^\circ)$ gives the best balance, so it is the strongest base.The tertiary amine $(3^\circ)$ suffers steric hindrance and poor solvation, so it is weaker than the secondary amine.The primary amine $(1^\circ)$ has less $+I$ effect than the secondary amine, so it is weaker still.Unsubstituted $NH_3$ has no alkyl group and is therefore the weakest base.Hence the order is: $(C_2H_5)_2NH > (C_2H_5)_3N > C_2H_5NH_2 > NH_3$.Answer:The correct order is $(C_2H_5)_2NH > (C_2H_5)_3N > C_2H_5NH_2 > NH_3$.