19

2.8.2.Reactions of benzene diazonium salts

Substitution

Sandmeyer reaction

Mechanism

Preparation of iodoarenes

Preparation of fluoroarenes

Preparation of phenols

Preparation of thiols

Reduction of diazonium salts

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NX
2

R

Cl

R

Br

R
CN

R

CuCl

CuBr

CuCN

+N2

+N2

+N2

an entry into carboxylic acids

strong enthalpic
driving force

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NX
2

R

R

R

Cl

R

+CuCl

+CuCl2

+CuCl2

+CuCl

= Cl

X

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NX
2

R

I

R

KI

+N2+KX

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NBF
24

R

F

R

∆

+N2+BF3

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F

R

NX
2

R

H2SO4

+N2+HX

+H2O

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S

R

NX
2

R

O

KS

OEt

O

OEt

SH

R

+N2+KX

+

H+/ H2O

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H

R

NX
2

R

+H3PO2+H2O

+H3PO3+HX

oxidised