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

Explanation

Williamson.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)-overset(* *) underset (* *)O-underset(CH_(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.halide is used, an alkene is the only reaction product and no ether is 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-C=CH_(2))+NaBr+CH_(3)OH`