Basicity of Amines + Diazonium Reactions
Nitrogen Compounds
40
JEE Qs
7%
Hard
90
min
Master the basicity trends by understanding the contributing electronic and steric factors, and meticulously memorize the reagents, conditions, and products for each specific diazonium reaction.
🧮 Key Formulas
✅ Key Points for JEE
- 1Basicity of amines depends on the availability of the lone pair of electrons on nitrogen, influenced by inductive effects (+I increases, -I decreases), resonance (delocalization decreases), solvation effects (stabilization of conjugate acid by H-bonding), and steric hindrance (impedes solvation and protonation).
- 2Aliphatic amines are stronger bases than ammonia due to +I effect of alkyl groups. Aromatic amines are weaker bases than ammonia due to resonance delocalization of the lone pair into the benzene ring.
- 3The basicity order of alkyl amines in aqueous solution (e.g., for ethyl amines: (C2H5)2NH > (C2H5)3N > C2H5NH2 > NH3) is determined by a combination of +I effect, steric hindrance, and solvation effects, with solvation being crucial. In the gas phase, only the +I effect and steric factors are relevant, leading to (CH3)3N > (CH3)2NH > CH3NH2 > NH3.
- 4Diazotization is the reaction of primary aromatic amines with nitrous acid (generated in situ from NaNO2/HCl) at 0-5°C to form diazonium salts. This low temperature is critical to prevent decomposition.
- 5Aromatic diazonium salts are highly reactive intermediates, not typically isolated, and are used directly for various substitution and coupling reactions to synthesize a wide range of organic compounds.
- 6The nitrogen molecule (N2) is an excellent leaving group in diazonium reactions, driving many of the transformations.
⚠️ Common Mistakes
- ✕Confusing the basicity order of alkyl amines in the aqueous phase versus the gas phase.
- ✕Forgetting the critical 0-5°C temperature requirement for diazotization, which can lead to alcohol formation (for aliphatic amines) or decomposition (for aromatic diazonium salts) if the temperature is higher.
- ✕Incorrectly identifying the products or reagents for Sandmeyer vs. Gattermann reactions, especially for the formation of aryl halides.
- ✕Not recognizing the effect of electron-donating or electron-withdrawing groups on the basicity of aromatic amines.
- ✕Trying to isolate or store diazonium salts (except specific tetrafluoroborates) due to their inherent instability.
📝 Practice Questions
See allQ56.Given below are two statements : Consider the following reaction (1) Both Statement I and Statement II are false (2) Statement I is true but Statement II is false (3) Statement I is false but Statement II is true (4) Both Statement I and Statement II are true
Q56.Identify correct statements : (A) Primary amines do not give diazonium salts when treated with NaNO2 in acidic condition. (B) Aliphatic and aromatic primary amines on heating with CHCl3 and ethanolic KOH form 2025 (28 Jan Shift 2) JEE Main Previous Year Paper carbylamines. (C) Secondary and tertiary amines also give carbylamine test. (D) Benzenesulfonyl chloride is known as Hinsberg's reagent. (E) Tertiary amines reacts with benzenesulfonyl chloride very easily. Choose the correct answer from the options given below : (1) (A) and (B) only (2) (D) and (E) only (3) (B) and (D) only (4) (B) and (C) only
Q68.Match the Compounds (List - I) with the appropriate Catalyst/Reagents (List - II) for their reduction into corresponding amines. Choose the correct answer from the options given below : (1) (A)-(II), (B)-(I), (C)-(III), (D)-(IV) (2) (A)-(III), (B)-(II), (C)-(IV), (D)-(I) (3) (A)-(II), (B)-(IV), (C)-(III), (D)-(I) (4) (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
Q58.The correct set of ions (aqueous solution) with same colour from the following is: 2025 (23 Jan Shift 1) JEE Main Previous Year Paper (1) Sc3+, Ti3+, Cr2+ (2) V2+, Cr3+, Mn3+ (3) Ti4+, V4+, Mn2+ (4) Zn2+, V3+, Fe3+
Q66. For reaction The correct order of set of reagents for the above conversion is : (1) Br2 ∣FeBr3, H2O(Δ), NaOH (2) H2SO4, Ac2O, Br2, H2O(Δ), NaOH (3) Ac2O, Br2, H2O(Δ), NaOH (4) Ac2O, H2SO4, Br2, NaOH
Q55.Total number of nucleophiles from the following is : ⊖ NH3, PhSH, (H3C)2 S, H2C = CH2, O H, H3O⊕, (CH3)2CO, ⇌NCH3 (1) 7 (2) 4 (3) 6 (4) 5
NCERT Chapters
- Class 12 Chemistry Part II Ch 13: Amines