1. Amines

2.  Amines are formed by replacing one or more hydrogen atoms of ammonia (NH 3 ) with alkyl groups.  In nature, they occur among proteins, vitamins, alkaloids and hormones. Synthetic examples include polymers, dyestuffs and drugs.  Two biologically active compounds, namely adrenaline and ephedrine, both containing secondary amino group, are used to increase blood pressure.

3. Structure of Amines Nitrogen orbitals in amines are sp 3 hybridized also the geometry of amines is pyramidal. Every of the three sp 3 hybridized orbitals of nitrogen are related with orbitals of hydrogen or carbon depending ahead the composition of the amines N CH 3 H3CH3C H3CH3C

4. It is one of the most important of all the amines. Aniline

5.  CLICK

6. Nitro Benzene Reduction with Iron scrap with Hydrochloric acid is preffered because FeCl2 formed in reaction get hydrolysed and release HCl hence small amount of HCl is required to initiate the reaction Tin and Hydrochloric Acid BACK

7. From Nitro Alkanes Other reducing agents Sn/Conc. HCl, H 2 /Ni BACK

8.  The process of cleavage of the C–X bond from an alkyl or benzyl halides by ammonia molecule is known as ammonolysis. The order of reactivity of halides with amines is RI > RBr >RCl.

9. From Acid Amide See number of carbon atoms remains same after reduction BACK

10. See the number of carbon atom get reduced by one From Hoffman degradation method BACK

11. From acid nitrile Other reducing agents: H 2 / Ni 140 o C Na / ethanol BACK

12. From Haloalkane Further substitution give mixture of products. BACK

13. With “fishy”smell. Soluble in water due to H-bond formation. Aromatic amine are liquid with high boiling point with a characteristic fishy smell and insoluble in water. Physical Properties

14. Chemical Properties Basic character Basic strength depends on the availability of lone pair e - on N and solubility in water (stability of the conjugate cation).

15. Basic character (cont’d) Inductive effect: Due to the alkyl group (e- donating group) 3 o > 2 o > 1 o > NH 3 BUT Ease of solvation of protonated amine: Due to the formation of H-bond between N- H and H 2 O NH 3 > 1 o > 2 o > 3 o Overall effect: 2 o  1 o > 3 o >NH 3

16. Basic character (cont’d) Comparing ammonia, CH 3 NH 2 & (CH 3 ) 2 NH, basic strength increased as more alkyl groups attached to the N atom. Alkyl group is e- donating group which makes the lone pair of e- of N more available to co-ordinate with a proton.

18. Basic character (cont’d) Aromatic amines are less basic strength than aliphatic amines. This is because the lone pair e- of N can overlap with the pi-molecular orbital of the benzene ring. It is thus less available to co-ordinate with a proton.

19. Resonance Structure of Aniline Electron releasing groups:–OCH 3, –CH 3 increase basic strength Electron withdrawing groups : NO 2, –SO 3, –COOH, –X decrease it.

20. Basic character (cont’d) For acid amide, it is even less basic strength than aromatic amine. This is because the negative inductive effect of the C=O which makes the lone pair e - on N less available. Moreover, lone pair e - on N can ovrelap with p-orbitals of C.

21.  Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances.

22. RNH 2 + HCl  RNH 3 + Cl - (white fume) Test for amine

23. Alkylation (nucleophilic substitution of RX) Such method will give mixture of products.

24. Acylation (ammonolysis of acid derivative)

25. Benzoylation

26. Reaction With HONO

27. Diazonium coupling

28. By Catalytic Hydrogenation The catalytic hydrogenation of nitro group takes place smoothly in presence of finely divided nickel or platinum catalyst

29. Classification of Amines Primary Amines Characteristic group of primary Amine

30. Secondary Amines Characteristic group of Secondary Amine

31. Tertiary Amines

32. The diazonium salts have the general formula–RN 2 + X - where R standsfor an aryl group and–X ion may be Cl– Br,– HSO 4 −, BF 4 −, etc. The stability of arenediazonium ion is explained on the basis of resonance.

33.  Benzenediazonium chloride is a colourless crystalline solid.  It is readily soluble in water and is stable in cold but reacts with water when warmed.  It decomposes easily in the dry state. Benzenediazonium fluoroborate is water insoluble and stable at room temperature.

34.  It is clear that the diazonium salts are very good intermediates for the introduction of –F, – Cl, –Br, –I, –CN, –OH,–NO 2 groups into the aromatic ring.  Aryl fluorides and iodides cannot be prepared by direct halogenation.  The cyano group cannot be introduced by nucleophilic substitution of chlorine in chlorobenzene but cyanobenzene can be easily obtained from diazonium salt.