Explain the following reactions.
Williamson's Ether Synthesis Aldol condensation

Explanation

Willamson.s ether synthesis: It is an important method for the preparation of symmetrical and unsymmetrical-ethers. In this method, an alkyl halide is allowed to react with sodium alkoxide.
`R-X +R- overset(-) overset(* *) underset(* *)O overset(+)(Na) to R- underset(* *) overset(* *)O-R+NaX`
Ethers containing substituted alkyl groups `(2^(@) or 3^(@))` may . also be prepared by this method. The reaction involves `S_(N)2` attack of an alkoxide ion on primary alkyl halide.
`CH_(3)-underset(CH_(3)) underset(|) overset(CH_(3)) overset(|)(C)overset(-) overset(* *) underset( * *) O overset(+)(Na) +CH_(3)-Br to CH_(3)- underset(* *)overset(* *)O- underset(H_(3)) underset(|)overset(CH_(3)) overset(|)(C)-CH_(3)+NaBr`
In case of secondary and tertiary alkyl halides elimination competes over substitution. If a tertiary alkyl ha de is used, an alkene is the only reaction product and no eth ris formed.
`CH_(3)-underset(CH_(3)) underset(|) overset(CH_(3)) overset(|)(C)-Br + overset(+)(Na) overset(-) overset(* *) underset( * *) O-CH_(3) to underset("2-Methyl propene") underset(CH_(3)) underset(|)(CH_(3)-C=CH_(2))+NaBr+CH_(3)OH`