Title 22. Nitrogen Containing Compounds.pdf ✅

Nitrogen Containing Compounds 381 22 Nitrogen Containing Compounds QUICK LOOK Nitro alkanes are derivatives of alkanes. They are isomeric to nitrites (esters) classified as primary, secondary and tertiary depending on the nature of carbon atom to which nitro group is linked. −NO2 group is an ambident group. If it attacks through nitrogen It is called nitro and if it attacks through oxygen atom, it is called nitrite. Hence nitrites and nitro compounds are isomers. is isomeric with (Nitrite) R — O — N O == Structures Evidences show that nitrogen is attached to one of the oxygen atoms by a double bond and to the other by a dative bond. The resonance hybrid is shown as under which confirms the spectroscopic evidence that both nitrogen–oxygen bonds have same bond length. Out of three 2 sp hybrid orbitals of nitrogen one overlaps with alkyl group and two with oxygens while the unhybridized p-orbital of N-atom containing a pair of electrons and lying perpendicular to the plane of hybrid orbitals overlaps sideway with half filled 2p-orbitals of two oxygen atoms. This forms π -bond above and below the plane of molecule. Amides Cynadies (RCN) and Isocynides (RCN): These are the compounds containing —C N ≡≡ functional group. They have general formula R — C N. ≡≡ Preparation of Cynaides: The following methods can be employed to prepare the cynides. (Main product) RX KCN(alc) RCN KX + → + Aryl cyanides cannot be prepared by this method because aryl halides are less reactive towards nucleophilic substitution. Heat RCONH P O RCN H O 2 2 5 2 + → + KCN C H N Cl CuCN C H CN CuCl 6 5 2 6 5 + − + → + 3 2 (CH CO) O / 2 (Aldoxime) RCH NOH RC N H O ∆ == → ≡≡ + Dry/ether RMgX ClCN R — C N Mg(Cl)X + → ≡≡ + Preparation of Isocynides C H OH 2 5 (Major product) RX AgCN RNC AgX + → + RNH CHCl 3KOH RNC 3KCl 3H O 2 3 2 ∆ + + → + + (Carbylamine reaction) Reactions of Isocynides: Some of the important reactions of isocyanides are given below 2 O || R — C — NH HCl – RCONH CI 4 → + Hgo 2 2 → + (RCONH) Hg H O Na 1 2 2 → + (RCONH)Na H Br / 4KOH 2 → + + + RNH K CO 2KBr H O 2 2 3 2 H / Pt or LiAlH 2 4 → RCH NH 2 2 HNO2 → + RCOOH N2 P O / 2 5 RC N ∆ → ≡≡ NaOH → + RCOONa NH3 H O H 2 RCOOH NH4 + → + + + R — N + O O − ←→ O O − R — N + R — N + O O δ δ − ≡≡ − Resonating forms Hybride structure (Nitro) O R — N O O —N O       R R R C — NO2 Tertiary nitro alkane R R CHNO2 Secondary nitro alkane RCH NO 2 2 Primary nitro alkane
382 Quick Revision NCERT - CHEMISTRY Nitro Compounds (RNO2) Preparation of Aliphatic nitro Compounds Alcohol 2 2 Heat Alkyl nitrite Nntroalkane (Minor) (Major) 2RX 2AgNO RNO R O N O + → + − − = 2 Alkyl nitrite (X may be Nntroalkane (Minor) Br or I) (Major) 2RX 2K (O N O) R O N O RNO + + − = → − − = + 700K 3 3 3 3 2 2 2 Vapour Fuming Nitroethane CH CH HNO CH CH NO H O − + → + Preparation of Aromatic Nitro Compounds: They are obtained by nitration of arenes with nitrating mixture 2 4 3 (H SO HNO ) + . This chemical reaction is typical example of electrophilic ring substitution. Here, conc. H2SO4 reacts with HNO3 to produce nitronium ion 2 (NO ) + which acts as an electrophile while aerne behaves as the nucleophile. Amines: These are derivatives of ammonia. They can be classified into primary, secondary or tertiary amines if they have functional groups —NH , 2 | —NH — N | | respectively. Alkyl amines: RNH , 2 Aryl amines: ArNH2 (e.g. C H NH ), 6 5 2 Arlylalkyl amines: ArCH NH (e.g., C H CH NH ) 2 2 6 5 2 2 Preparation of Amines Reduction of alkyl cyanides: 2 4 2 2 RCN (H /Ni or LiAlH ) RCH NH + → (1 Amine) ° Reduction of isocyanides: 2 3 RNC H / Pt RNHCH + → (2 Amine) ° Reduction of alkanamides: RCONH (H / Pt or LiAlH ) RCH NH 2 2 4 2 2 + → Reduction of aldoximes: 2 4 Na / alc. or H / Pt RCH NOH 4[H] RCH NH H O or LiAlH 2 2 2 = + + → Hydrolysis of isocyanate: R N C O 2KOH RNH K CO − = = + → +2 2 3 Hoffmann’s bromide reaction: 2 2 2 2 3 2 Amide RCONH Br 4KOH RNH 2KBr K CO 2H O + + → + + + Hydrolysis of isocyanides: HCl RNC HOH RNH HCOOH + → +2 Ammonolysis of halides: 3 2 (Excess) RX NH RNH HX + → + Ammonolysis of alcohols: 2 3 575K, Al O ROH NH RNH H O + → + 3 2 2 Reduction of nitro compounds: Sn/HCl C H NO 6[H] C H NH 6 5 2 6 5 2 + → Gabriel’s Phthalimide synthesis Action of Heat: α-amino acids lose two molecules of water and form cyclic amides. β -amino acids lose a molecule of ammonia per molecule of amino acid to yield α,β-unsaturated acids. 3 2 2 NH Acrylic acid ( , -unsaturated acid) 3 CH — CH — COOH CH CH — COOH | | NH H α β ∆ → == − C — NH || O O || NH — C CH — R R — CH → CHR 2H O + 2 α-amino acid CH — R R — CH →∆ RCH C — OH HN || O O || NHHO — C 2 (1 Amine) RNH ° + N R H O/ H 2 + − → C || O O || C O || C — OH C — OH || O R X NK KX − → − 2 KOH(alc.) NH→ −H O C || O O || C C || O O || C 2 4 conc. H SO 3 2 + → + conc. HNO H O NO2 R N C − = 2HgO 2 (Alkyl isocyanate) R— N C O Hg O → == == + + ,Isomerisation R N (More stable) → ≡≡ ∆ 1 8 S8 (Alkyl isothiocyanate) → == == R— N C S Cl2 2 (Alkyl iminocarbonyl chloride) R— N CCl → == + Na /CC H OH(Reduction) 2 5 →RNH—CH3 2HOH/ H RNH HCOOH 2 + → + O3 2 (Alkyl isocyanate) R— N C O O → == == + +
Nitrogen Containing Compounds 383 MULTIPLE CHOICE QUESTIONS Amines 1. The correct order of basicity of amines in water is: a. 3 2 3 3 3 2 (CH ) NH (CH ) N CH NH > > b. CH NH (CH ) NH (CH ) N 3 2 3 2 3 3 > > c. 3 3 3 2 3 2 (CH ) N (CH ) NH CH NH > > d. 3 3 3 2 3 2 (CH ) N CH NH (CH ) NH > > 2. Complete the following reaction: R NH H SO 2 2 4 + → a. 3 4 [R NH ] HSO + − b. 2 3 2 4 [R NH ] SO + − c. R NH .H SO 2 2 4 d. No reaction 3. Among the following which one does not act as an intermediate in Hofmann rearrangement? a. RNCO b. .. RCO N c. .. RCO N HBr d. RNC 4. Aniline reacts with which of these to form Schiff base? a. Acetic acid b. Benzaldehyde c. Acetone d. NH3 5. Which of the following does not reduce Tollen’s reagent? a. CH CHO 3 b. C H NHOH 6 5 c. HCOOH d. C H NO 6 5 2 6. Which one of the following compound is most basic? (A) (B) (C) a. (A) b. (B) c. (C) d. All are equally basic 7. POCl3 pyridine R NH COH − − → product In the given reaction what will be the product? a. R – N = C = O b. R N C + − − ≡ c. R C N − ≡ d. None of these 8. Which of the following is secondary pollulant? a. CO2 b. N2O c. PAN d. SO2 9. Nitration of aniline also gives m-nitro aniline, in strong acidic medium because: a. In electrophilic substitution reaction amino group is meta directive b. Inspite of substituents nitro group always goes to m- position c. In strong acidic medium, nitration of aniline is a nucleophic substitution reaction d. In strong acidic medium aniline present as anilinium ion 10. Diazo-coupling is useful to prepare some: a. Dyes b. Proteins c. Pesticides d. Vitamins Introduction of Nitrogen Containing Compounds 11. C H N 3 9 represents: a. Primary amine b. Secondary amine c. Tertiary amine d. All of these 12. Allyl isocyanide has: a. 9 sigma bonds and 4 pi bonds b. 8 sigma bonds and 5 pi bonds c. 8 sigma bonds, 3 pi bonds and 4 non-bonding electrons d. 9 sigma bonds, 3 pi bonds and 2 non-bonding electrons 13. Acetonitrile is: a. C H CN 2 5 b. CH CN 3 c. CH COCN 3 d. C H CH CN 6 5 2 14. Acetanilide can be prepared from aniline and which of the following? a. Ethanol b. Acetaldehyde c. Acetone d. Acetic anhydride 15. Aniline is usually purified by: a. Steam distillation b. Simple distillation c. Vacuum distillation d. Extraction with a solvent Preparation of Nitrogen Containing Compounds 16. Amides may be converted into amines by reaction named after: a. Perkin b. Claisen c. Hoffmann d. Kolbe 17. When methyl iodide is heated with ammonia, the product obtained is? a. Methylamine b. Dimethylamine c. Trimethylamine d. A mixture of the above three amines 18. Which of the following reactions does not yield an amine? a. RX NH + → 3 b. 2 5 Na C H OH RCH NOH [H] = + → c. H RCN H O2 + + → d. LiAlH4 RCONH 4H 2 + → | H N | N H O | H N | N H
384 Quick Revision NCERT - CHEMISTRY 19. Which of the following gives RNC, when reacted with CHCl3 and KOH? a. RNH2 b. R NH 2 c. R N3 d. R N Cl 4 + − 20. Nitrobenzene combines with hydrogen in the presence of platinum to produce: a. Toluene b. Benzene c. Aniline d. Azobenzene 21. When chlorobenzene is treated with NH3 in presence of Cu2O in xylene at 570 K. The product obtained is? a. Benzylamine b. Diazonium salt c. Schiff’s base d. Aniline 22. In the series of reaction 2 2 2 NaNO / HCl HNO 6 5 2 2 0 5 C CH O C H NH X Y N HCl − ° → → + + X and Y are respectively: a. C H N N C H ,C H N Cl 6 5 6 5 6 5 2 ⊕ Θ − = − b. C H N Cl ,C H N N C H 6 5 2 6 5 6 5 ⊕ Θ − = − c. C H N Cl ,C H NO 6 5 2 6 5 2 ⊕ Θ d. C H NO ,C H 6 5 2 6 6 23. Aromatic nitriles (ArCN) are not prepared by reaction: a. ArX + KCN b. ArN CuCN 2 + + c. ArCONH P O 2 2 5 + d. ArCONH SOCl 2 2 + 24. In acid medium nitrobenzene is reduced to aniline as shown in the reaction C H NO 6[H] C H NH 2H O 6 5 2 6 5 2 2 − + → − + The reducing agent used in this reaction is ....... a. LiAlH4 b. Sn/HCl c. Na/alcohol d. H /Ni 2 25. Na ROH CH CONH Z H O. 3 2 2 → + + What is Z ? a. CH CH NH 3 2 2 b. CH CH NC 3 2 c. CH CH CH 3 2 3 d. NH CONH 2 2 26. Ethylamine can be prepared by the action of bromine and caustic potash on: a. Acetamide b. Propionamide c. Formamide d. Methyl cyanide 27. Which one of the following compound gives a secondary amine on reduction? a. Nitromethane b. Nitrobenzene c. Methyl isocyanide d. Methyl cyanide 28. In this reaction C H NH HCl NaNO X. 6 5 2 2 + + → Product X is: a. Aniline hydrochloride b. Nitro aniline c. Benzenediazonium chloride d. None of these 29. Which of the following compound is the strongest base? a. Ammonia b. Aniline c. Methylamine d. N-methyl aniline Properties of Nitrogen Containing Compounds 30. Which of the following compound is expected to be most basic? a. Aniline b. Methylamine c. Hydroxylamine d. Ethylamine 31. Which of the following compounds is an amino acid? a. || 3 2 4 O CH CH C O NH − − − − b. || 3 | 2 O CH CH C OH NH − − − c. || 3 2 2 O CH CH C NH − − − d. || 3 | 2 O CH CH C Cl NH − − − 32. Which of the following amines would undergo diazotisation? a. Primary aliphatic amines b. Primary aromatic amines c. Both a. and b. d. None of these 33. Which one is weakest base? a. Ammonia b. Methylamine c. Dimethylamine d. Trimethylamine 34. Which of following is not an usual method for preparation of primary amine? a. Hofmann's method b. Curtius reaction c. Schmidt reaction d. Friedel-Craft's reaction 35. A solution of methyl amine: a. Turns blue litmus red b. Turns red litmus blue c. Does not affect red or blue litmus d. Bleaches litmus