Download Preparation of ethers:

Preparation of ethers:
Williamson Ether Synthesis
General reaction:
SN2
RONa + R'Br
ROR' + NaBr
prepare alkoxide
OH
ONa
2 Na
2
2
+ H2
OCH2CH3
Na O
+ CH3CH2
Br
+ NaBr
This is an SN2 reaction, thus the alkyl halide should be primary or methyl.
Dehydration of Alcohols to make symmetrical ethers
OH
2
H 3O
H2SO4(aq) 140oC
O
+
H 2O
OH2
H
O
+ H 2O
Alkoxymercuration/demercuration
OCH3
1) Hg(OAc)2
in CH3OH
2) NaBH4
Mechanism is Markovnikov oxymercuration
HgOAc OAc
+
δ OAc
Hg
Hg(OAc)2
in CH3OH
Hg
δ
Hg
+
OCH3
H
OAc
OCH3
OAc
H
NaBH4 (H )
OCH3
OCH3
H
Reactions of ethers:
Cleavage with HI or HBr
H
Br
HBr
O
H
O
Br
SN2
OAc
Br
OH
+
examples (provide the mechanism):
O
OH
HI
I
OCH(CH3)2
HBr
E2
OH
+ CH2=CHCH3
+ HBr