ETHERS AND EPOXIDES
R-O-R'
ethers
types
R-O-R'
R-O-R
unsymmetrical
symmetrical
examples
CH3-O-CH3
(di)methyl ether
C6H5-O-C6H5
CH3-O-C2H5
ethyl methyl ether
CH3-O-C6H5
methyl phenyl ether
(di)phenyl ether
Nomenclature:
Common names: ether is named as alkyl ether or alkyl alkyl ether
IUPAC names: ether is named as alkoxy alkane (where small alkane is alkoxy)
compound
CH3-O-CH3
Common name
Methyl ether
IUPAC name
Methoxy methane
CH3-O-C2H5
Methyl ethyl ether
Methoxy ethane
C6H5-O-C6H5
Phenyl ether
Phenoxy benzene
C6H5-O-C3H7
Propyl phenyl ether Propoxy benzene
Chemistry of Anisole: methyl phenyl ether OR methoxy benzene
OH
ONa
CH3I
CH3N2
Na-phenoxide
O
phenol
CH3
Anisole
HI/cold
OH
+
phenol
HI/hot
I
CH3I
+ CH3I + H2O
Phenyl iodide
Gravimetric estimation of methoxy group (Ziesel’s method)
Principle:
403 oC
R-OCH3
CH3I
+
+
HI
AgNO3
RI
+
CH3I
CH3NO 3
+
+
H2O
AgI
Methoxy ether converted to methyl iodide which on reaction with AgNO3
precipitates equivalent AgI, from the weight of which, wt and number of methoxy
group is calculated.
Procedure: A known weight of methoxy compound is taken in a long neck
distillation flask and 15 CC of Conc. HI is added. To avoid bumping, few pieces of
porcelain added. The flask is heated to get the vapours of CH3I which are sweeped by
CO2 gas to get absorbed in the alcoholic AgNO3 solution kept in absorption flasks.
The precipitate of AgI formed in the flasks is filtered, dried and weighed.
Relation:
one mole of AgI ≡ one mole of CH3I ≡ one mole of methoxy group
235 gm of AgI ≡ 31 gm of methoxy group
Problem: 0.070 × 10-3 kg of methoxy compound on Ziesel’s estimation, gave 0.154 ×
10-3 kg of Ag I, if molecular wt of the methoxy compound is 108, calculate % and
number of methoxy group in it.
Solution:
one mole of AgI ≡ one mole of CH3I ≡ one mole of methoxy group
235 gm of AgI ≡ 31 gm of methoxy group
-3
∴0.154 × 10 kg of Ag I≡ 0.154 × 10 -3 ×31÷235 = 0.02031× 10 -3 kg of methoxy gr.
As 0.070 × 10 -3 kg of methoxy compound ≡ 0.02031× 10-3 kg of methoxy gr.
1 mole i.e. 108 gm of methoxy compound ≡108 × 0.02031× 10-3 ÷0.070 × 10 -3 gm of
methoxy gr.
= 31.3354 gm of methoxy gr.
Number of methoxy groups: weight of methoxy groups÷ mol. Wt of methoxy group
Number of methoxy group=31.3354 ÷31
= 1.011≈1
(As weight of 1 methoxy group is 31, number of methoxy groups is approximately 1.)
Epoxides:
Epoxides are cyclic ethers containing three membered epoxide ring which is called
oxirane ring. Examples: ethylene oxide, propylene oxide.
H
H2C CH2
CH2 C CH2
O
O
O
epoxide/oxirane ethylene oxide propylene oxide
or
or
epoxy ethane epoxy propane
CH3
H
H3C
O
CH3
O
3-methyl-2,3 epoxy butane 1,2-epoxy cyclohexane
Nomenclature:
Common names: Epoxides are named as alkylene oxides as above.
IUPAC: Epoxides are named as epoxy alkane.
Chemistry of epoxy ethane:
H2C CH2+ 1/2 O2
Ag,
H+
523 K
Heat
R OH H O R OLi
2
ether
H+
H-OH
R-Li
H+
H2O
OH OH
H+
H-Cl
ether
R
OMgX
H+
H-Br
O
epoxy ethane
RMgX
OH Cl
OH Br
H+
H-NH2
OH NH2
OH-
OH-
H-OEt
H-OMe
HCN
H+
H-SCH3
OH CN
OH SCH3
OH OEt
OH OMe