Aliphatic amines part II
- 3. Lower members aliphatic amines ammonia smell Higher members fishy smell physical sate Boiling points polar compounds Form molecular hydrogen bonding Amines higherbioling points N H R H H N H N H R H R H Solubility amines soluble in water less in polar solvents eg.organic solvents H N H R O H HH N R H
- 4. Chemical properties Basicity of amine R NH2 + HCl R NH Cl 3 + - 1 0 amine Salt R NH2 + H2O R NH2OH R NH3 + OH + _ + _ R NH2 + H2O R NH3 + OH + _ Kb = (R NH3) (OH) + (RNH2) pK b = -logKb smaller value of pKb Stronger basicity of amine
- 5. pKb values of amines CH3NH2 3.36 CH3 CH2 NH2 3.25 (CH3)2 NH 3.28 (CH3)3 N 4.30 C6H5NH2 9.42 C6H5NHCH3 9.15 C6H5 N(CH3)2 8.95 (C6H5)2 NH 13.20 Compond pKb
- 6. (1)Aliphatic amines are stronger bases than ammonia (2)Relatives Basicity of primary, secondary & tertiary amines NH 3 R NH2 NH 3 R NH2 R NH R 1 amine 2 amine0 0 .... .. Ammonia Ammonia 3 NH > CH NH > (CH ) N 323 3 (CH )2 secondary amine>primary amine>tertiary amine
- 7. Basis of factors Inductive effect Solvation effect 3 NH > CH NH > (CH ) N 323 3 (CH )2 3 NH(CH )2(CH3)3 N > > CH3NH2 3 2 1 0 0 0 1 0 R NH2 > R2 NH > R3N 2 3 R2 NH > R NH2 > R2N 2 1 3 0 0 0 0 0 NH2 2 1 0 0 pKb=3.36 4.303.28 3 0 CH3)3N(CH3)2 NH CH3 ammonium ion from primary amine maximum solvation secondary amine ammonium ion from tetiary amine manimum solvation
- 8. Aromatic amines weak base aliphatic amines & ammonia NH2: I NH2 + - NH2 + - NH2 + - NH2 II III IV V + H2O + OH - NH2NH2 + anilinium ion NH3 NH3 ++
- 9. N Alkyl anilines are stronger bases than aniline N CH3 CH3 > H N CH3 > NH2 N,N-dimethylamine pKb=8.95 N-Methylamine 9.15 aniline 9.42
- 10. LETS GO AHEAD & SEE AGAIN