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Nitrogen compounds. (Chapter 37). CH 3. NO 2. NO 2. NO 2. Nitrogen containing compound. T.N.T. Proteins Enzymes Drugs. R-N-H R ’. R + R-N-R ” Br - R ’. R-N-R ” R ’. NH 2. Amines. Aliphatic 1 o amine 2 o amine 3 o amine 4 o ammonium cpds Aromatic.

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nitrogen compounds

Nitrogen compounds

(Chapter 37)

nitrogen containing compound

CH3

NO2

NO2

NO2

Nitrogen containing compound
  • T.N.T.
  • Proteins
  • Enzymes
  • Drugs
amines

R-N-H

R’

R +

R-N-R” Br-

R’

R-N-R”

R’

NH2

Amines
  • Aliphatic
    • 1o amine
    • 2o amine
    • 3o amine
    • 4o ammonium cpds
  • Aromatic

R-NH2

iupac names
IUPAC names
  • CH3NH2 Methanamine
  • (CH3)2NH N-methylmethanamine
  • (CH3)3N N,N-dimethylmethanamine
  • C6H5NH2 Phenylamine (aniline)
formation of amines
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+)

formation of amines6
Formation of Amines
  • C6H5-NO2 C6H5-NH2

Reducing agent:

H2/Ni

or

HCl,Fe (or Zn, Sn, SnCl2) then OH-

basicity of amines8

R

R

H

+

O

H

H

H

N:

N

H

OH-

H

H

Basicity of Amines

Order of basicity:

2o > 1o > 3o > NH3 > C6H5NH2

Why?

explanation

R

+

H

N

H

H

Explanation
  • Solvation of protonated amine in water by hydrogen bonding (more H, better solvation)
  • NH3>1o>2o>3o

H2O

H2O

H2O

explanation10

R

R

N:

R

+

R

R

H

N

R

Explanation
  • Effect of the inductive electron push of the R groups
    • Increase the basicity
    • Stabilize the alkylammonium ion
  • 3o>2o>1o>NH3
explanation11

..

NH2

..-

+

NH2

Explanation
  • Lone pair e- partly incorporated into benzene ring
  • Less ready for protonation
reactions

NaOH

NH2 + HCl

NH3+ Cl-

NH2 + H2O

+ NaCl

Reactions
  • Salt Formation

?

reactions13

O O

R-NH2 + CH3CCl  CH3CNHR + HCl

O O

R-NH2 + C6H5CCl  C6H5CNHR + HCl

High m.p.

Used in identification

Reactions
  • Amide Formation
reaction with nitrous acid

RNH2 + NaNO2 + HCl  [RN+N]Cl-

Aliphatic

Diazonium salt

(unstable)

ROH

H2O

-H+

R+ + N2

C=C

(evolution of N2 serves

as a test for 1o amine)

X-

R-X

Reaction with Nitrous acid
  • HNO2 prepared by NaNO2 + HCl
  • 1o aliphatic amines
reaction with nitrous acid15

N+N Cl-

NH2 + NaNO2 + HCl

Reaction with Nitrous acid
  • 1o aromatic amine

(stable at temp.<5oC, greater stability by dispersing charge into the benzene ring)

mechanism

..

..

..

O

N+

N+

O

O

N

H2O+

N

O

HO

N

O

..

..

+

N

O

Ar

Ar

NH2

NH2

Mechanism

-H2O

H+

-H+

+

H+

..

..

+

Ar

NH

N

O

Ar

N

N

OH

Ar

N

N

OH2

..

-H2O

+

+

Ar

N

N:

Ar

N

N:

benzenediazonium salt
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
benzenediazonium salt19

CuCl

ArCl

CuBr

ArBr

CuCN

Ar-N2+

+ N2

ArCN

I-

ArI

H2O

ArOH

Benzenediazonium salt
  • Can be replaced by a variety of function groups
  • High yield
  • No multiple substitution
coupling reaction

..

OH

O-

N=N+:

1

+

NaOH

(Napthalen-2-ol)

Ice cold

1

N+= N-

HO

Coupling reaction

Orange II, Azo dye (1876)

Also serve as a test

for 1o aromatic amine