(a) Draw the structure of main product formed in the following reaction:  

(b) In the following reaction, A and B are

OR

(a)  Arrange the following in increasing order of dipole moment:

Toulene (I), m-dichlorobenzene (II), o-dichlorobenzene (III), p-dichlorobenzene (IV)

(b) Why chloroform is stored in closed dark coloured completely filled bottles. Give reason.

(a)  The products are But-2-ene and But1-ene 

(b)   The product A is 4-Chloro Acetophenone

        The product B is 2-Chloro Acetophenone

                                                                         OR

(a) The increasing order of dipole moment is

 IV < I < II < III

(b) To  avoid the formation of phosgene, chloroform is stored away from light and air.
In dark coloured bottles, no light can enter. Thus, oxidation of chloroform to phosgene can be avoided.
Thus, chloroform is stored in closed dark coloured bottles.
$2{\mathrm{CHCl}}_3+{\mathrm{O}}_2\stackrel{\text{ Sunlight }}{⟶}2{\mathrm{COCl}}_2+2\mathrm{HCl}$