22.16 Nitrosation of Alkylamines

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22.16Nitrosation of Alkylamines
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Nitrite Ion, Nitrous Acid, and Nitrosyl Cation

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Nitrosyl Cation and Nitrosation
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Nitrosyl Cation and Nitrosation

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Nitrosation of Secondary Alkylamines

H

H

• nitrosation of secondary amines gives an
  N-nitroso amine

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Example
NaNO2, HCl

H2O
(88-90)
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Some N-Nitroso Amines
N-nitrosodimethylamine(leather tanning)
N-nitrosopyrrolidine(nitrite-cured bacon)
N-nitrosonornicotine(tobacco smoke)
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Nitrosation of Primary Alkylamines
R
R
H

H
H

H

• analogous to nitrosation of secondary amines to
  this point

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Nitrosation of Primary Alkylamines
R
H

• this species reacts further

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Nitrosation of Primary Alkylamines
R
H
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Nitrosation of Primary Alkylamines
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Nitrosation of Primary Alkylamines
R

N
N
O



H
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Nitrosation of Primary Alkylamines
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Nitrosation of Primary Alkylamines

• nitrosation of a primary alkylamine gives an
  alkyl diazonium ion
• process is called diazotization

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Alkyl Diazonium Ions

• alkyl diazonium ions readily lose N2 to give
  carbocations

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Example Nitrosation of 1,1-Dimethylpropylamine
N2
H2O
(80)

(2)
(3)
Fig. 22.5 (p 890)
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Nitrosation of Tertiary Alkylamines

• There is no useful chemistry associated with the
  nitrosation of tertiary alkylamines.

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22.17Nitrosation of Arylamines
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Nitrosation of Tertiary Arylamines

• reaction that occurs is electrophilic aromatic
  substitution

1. NaNO2, HCl, H2O, 8C
2. HO
(95)
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Nitrosation of N-Alkylarylamines

• similar to secondary alkylamines
• gives N-nitroso amines

NaNO2, HCl,H2O, 10C
(87-93)
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Nitrosation of Primary Arylamines

• gives aryl diazonium ions
• aryl diazonium ions are much more stable
  thanalkyl diazonium ions
• most aryl diazonium ions are stable under the
  conditions of their formation (0-10C)

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Nitrosation of Primary Arylamines

• gives aryl diazonium ions
• aryl diazonium ions are much more stable
  thanalkyl diazonium ions
• most aryl diazonium ions are stable under the
  conditions of their formation (0-10C)

fast
slow


Ar
N2
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Example
HSO4
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Synthetic Origin of Aryl Diazonium Salts
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22.18Synthetic Transformations of Aryl Diazonium
Salts
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Transformations of Aryl Diazonium Salts
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Preparation of Phenols

• hydrolysis of a diazonium salt

H2O, heat
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Example
1. NaNO2, H2SO4 H2O, 0-5C
2. H2O, heat
(73)
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Transformations of Aryl Diazonium Salts
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Preparation of Aryl Iodides

• reaction of an aryl diazonium salt with potassium
  iodide

KI
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Example
I
1. NaNO2, HCl H2O, 0-5C
Br
2. KI, room temp.
(72-83)
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Transformations of Aryl Diazonium Salts
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Preparation of Aryl Fluorides

• heat the tetrafluoroborate salt of a diazonium
  ion
• process is called the Schiemann reaction

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Example
1. NaNO2, HCl, H2O, 0-5C
2. HBF4
3. heat
(68)
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Transformations of Aryl Diazonium Salts
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Preparation of Aryl Chlorides and Bromides

• aryl chlorides and aryl bromides are prepared by
  heating a diazonium salt with copper(I) chloride
  or bromide
• substitutions of diazonium salts that use
  copper(I) halides are called Sandmeyer reactions

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Example
NH2
Cl
1. NaNO2, HCl, H2O, 0-5C
2. CuCl, heat
NO2
NO2
(68-71)
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Example
1. NaNO2, HBr, H2O, 0-10C
Br
Cl
2. CuBr, heat
(89-95)
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Transformations of Aryl Diazonium Salts
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Preparation of Aryl Nitriles

• aryl nitriles are prepared by heating a diazonium
  salt with copper(I) cyanide
• this is another type of Sandmeyer reaction

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Example
1. NaNO2, HCl, H2O, 0C
CN
CH3
2. CuCN, heat
(64-70)
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Transformations of Aryl Diazonium Salts
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Transformations of Aryl Diazonium Salts

• hypophosphorous acid (H3PO2) reduces diazonium
  salts ethanol does the same thing
• this is called reductive deamination

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Example
NaNO2, H2SO4, H3PO2
(70-75)
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Value of Diazonium Salts

• 1) allows introduction of substituents such as
  OH, F, I, and CN on the ring
• 2) allows preparation of otherwise difficultly
  accessible substitution patterns

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Example
NaNO2, H2SO4,H2O, CH3CH2OH
(100)
(74-77)
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22.19Azo Coupling
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Azo Coupling

• Diazonium salts are weak electrophiles.
• React with strongly activated aromatic compounds
  by electrophilic aromatic substitution.

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Azo Coupling

• Diazonium salts are weak electrophiles.
• React with strongly activated aromatic compounds
  by electrophilic aromatic substitution.

an azo compound
Ar' must bear a strongly electron-releasing group
such as OH, OR, or NR2.
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Example

Cl