1. Nitrogen compounds
(Chapter 37)

2. Nitrogen containing compound
T.N.T.
Proteins
Enzymes
Drugs
CH3
NO2

3. Amines R-NH2 R-N-R” R’ R-N-H R’ R + R-N-R” Br- R’ Aliphatic Aromatic
1o amine
2o amine
3o amine
4o ammonium cpds
Aromatic
R-NH2
R-N-R” R’
R-N-H R’
R +
R-N-R” Br- R’
NH2

4. IUPAC names CH3NH2 Methanamine (CH3)2NH N-methylmethanamine
(CH3)3N N,N-dimethylmethanamine
C6H5NH2 Phenylamine (aniline)

5. Formation of amines Alkylation of NH3
RX + NH3  R-NH2 + R2-NH + R3N + R4N+X-
(NH3 in large excess, 1o amine as main product)
1o Amine from Amides and Nitriles
R-CN  RCH2NH2 (H2/Ni or LiAlH4)
RCONH2  RCH2NH2(LiAlH4 /ether than H+)

6. Formation of Amines C6H5-NO2  C6H5-NH2 Reducing agent: H2/Ni or
HCl,Fe (or Zn, Sn, SnCl2) then OH-

7. Basicity of Amines NH3 pKb = 4.74 CH3NH2 3.36 CH3CH2NH2 3.25
CH3CH2CH2NH2
3.33
(CH3)2NH
3.28
(CH3)3N
4.30
C6H5NH2
9.4

8. Basicity of Amines R H N: H O R H N + OH- Order of basicity:
2o > 1o > 3o > NH3 > C6H5NH2
Why?

9. Explanation
Solvation of protonated amine in water by hydrogen bonding (more H, better solvation)
NH3>1o>2o>3o R H N +
H2O
H2O
H2O

10. Explanation Effect of the inductive electron push of the R groups
Increase the basicity
Stabilize the alkylammonium ion
3o>2o>1o>NH3 R N: R N H +

11. Explanation Lone pair e- partly incorporated into benzene ring
Less ready for protonation
NH2 ..
NH2
..- +

12. Reactions
Salt Formation
NH2 + HCl
NH3+ Cl-
NH2 + H2O
+ NaCl
NaOH ?

13. Reactions Amide Formation O O R-NH2 + CH3CCl  CH3CNHR + HCl O O
High m.p.
Used in identification

14. Reaction with Nitrous acid
HNO2 prepared by NaNO2 + HCl
1o aliphatic amines
RNH2 + NaNO2 + HCl  [RN+N]Cl-
Aliphatic
Diazonium salt
(unstable)
H2O
ROH
R+ + N2
(evolution of N2 serves
as a test for 1o amine)
-H+
C=C X-
R-X

15. Reaction with Nitrous acid
1o aromatic amine
NH2 + NaNO2 + HCl 
N+N Cl-
(stable at temp.<5oC, greater stability by dispersing charge into the benzene ring)

16. Mechanism -H2O HO N O .. H+ N+ O .. H2O+ N O N O Ar NH2 .. Ar NH2 + N

17. Stability of Ar-N+N N N: +

18. Benzenediazonium salt
C6H5-N2+ Cl-
C-N bond heavily polarized away from benzene ring
C atom accept Nu: (against the norm of aromatic chemistry)
Has considerable synthetic value

19. Benzenediazonium salt
Can be replaced by a variety of function groups
High yield
No multiple substitution
Ar-N2+
CuCl
ArCl
CuBr
ArBr
CuCN
ArCN I-
ArI
H2O
ArOH
+ N2

20. Coupling reaction .. OH N=N+: O- + NaOH Ice cold1
(Napthalen-2-ol)
N+= N- HO
Ice cold 1
Orange II, Azo dye (1876)
Also serve as a test
for 1o aromatic amine