Preparation of methoxy benzene

(1) From alkyl halides

(ii) By heating alkyl halide with dry silver oxide

2RX + Ag2O ————→ R – O – R + 2AgX,

2C2H5Br + Ag2O ————→ C2H5OC2H5 + 2AgBr
Ethyl bromide Diethyl ether

(2) From alcohols

(i) By dehydration of alcohols

(a) With conc. H2SO4 at 140° C

ROH + HOR ——————→ ROR + H2O.
2 molecules of alcohol 140oC Ether

In this reaction alcohol must be present in excess.

This reaction is mainly applicable for the dehydration of primary alcohols. Secondary and tertiary alcohols form alkenes mainly.

When this reaction is carried out between different alcohols then there is a mixture of different ethers is obtained.

(b) With Al2O3 at 250° C:

2ROH ——————→ R – O – R + H2O

(ii) By the action of diazomethane on alcohols : This reaction is in presence of catalyst, boron trifluoride or HBF4.

ROH + CH2N2 ——————→ R – O – CH3 + N2

(a) This method is very useful for preparing mixed ethers.

(b) In higher cases, there can be 1, 2-hydride or 1, 2-methyl shift to form more stable carbonium ion.

(3) Reaction of lower halogenated ether with Grignard reagent

ROCH2X + XMgR' ——→ ROCH2R' + MgX2
Halogeneted Grignard Higher
ether reagent ether

(i) Higher members can be prepared by the action of grignard reagent on lower halogenated ethers.

(ii) Ether form soluble coordinated complexes with grignard reagent.

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