p-dichlorobenzene has higher melting point than those of ortho and meta isomers. Give reason.

Explanation

When methyl bromide undergoes hydrolysis with aqueoous potassium hydroxide , Methyl alcohol is formed .
`CH_3-Br+ KOH to CH_3-OH +KBr`
This mechanism involves only one step .

The nucleophile OH- attack from the rear side of the leaving group . A transition atate with partial formtion of C-OH bond and partial breaking f C+Br bond takes place simultaneously .
The rate of the reaction depends both on the concentration of nucleophile as well as alkyl halide Hence , It is a second order reaction . In `S_n^2` reaction , complete inversion of configuration takes place .
`R-OH+ SOCl_2 to R-Cl +SO_2 +HCl`
Swart.s Reaction
Due to symmetry of para - isomers