Preparation of Ether

ETHER

$\bullet$  R $-$ O$-$R¢ Alkoxy alkane (Di alkyl ether)

$\bullet$   R = R¢ Symmetrical ether.

     R $\ne$ R¢ Unsymmetrical or mixed ether.

     ‘O’ is to be counted with least number of C atom.

Example:

    ਌H₃$-$O$-$C₂H₅ Methoxy ethane

    ਌H₃$-$O$-$C₆H₅ Methoxy benzene

     There are various types of cyclic ethers also. 

PREPARATION OF ETHERS

(i) ਏrom 1º alcohol

     (a)   With H₂SO₄

     (b)   With diazomethane

            $R-O-H\underset{{\left(C_2{H}_{5}O\right)}_{3}Al}{\overset{C{H}_2{N}_2}{\to }}R-O-C{H}_3+N_2$

           (c)      ਊlcohol having at least one hydrogen at fourth carbon gives five membered cyclic ether with Pb(OAC)₄. The reaction is free radical reaction which is initiated by heat or light.

Williamson’s synthesis

$S_{N}2$ reaction of a sodium alkoxide with alkyl halide, alkyl sulphonate or alkyl sulphate is known as Williamson synthesis of ethers.

$R-ONa+RaposL\stackrel{S{N}_2}{\to }R-O-Rapos+NaL$

$\left[L=X,S{O}_{2}Raposapos,-O-S{O}_2-ORapos\right]$

$\bullet$ In this reaction alkoxide may be alkoxide of primary, secondary as well as tertiary alcohol.

$\bullet$ Alkyl halide must be primary.

$\bullet$ In case of tertiary alkyl halide, elimination occurs giving alkenes

$\bullet$ With a secondary alkyl halide, both elimination and substitution products are obtained. 

Illustration 1.  Write the product 

Solution

(3) From Alkane

(4) From Grignard reagent

     Higher ethers can be prepared by treating $\alpha$ - halo ethers with suitable reagents. 

(5) From Alkyl halide

     $2RI+\underset{dry}{A{g}_{2}O}\to R-O-R+2AgI$