(i) Chlorobenzene is stabilised by resonance and there is negative charge on 'CI' in 3 out of 5 resonating structures, therefore it has a lower dipole moment than cyclohexyl chloride in which there is no such negative charge.
(ii) Alkyl halides cannot form H-bond with water and cannot break H-bonds between water molecules, therefore they are insoluble in water.
(iii) Grignard reagents react with H₂0 to form alkanes, therefore they are prepared under anhydrous conditions.

(i) l-butanol
(ii) I-chlorobutane
(iii) but-l-ene
(i) \(\underset { 1-buanol }{ CH_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }Cl } \overset { P/{ I }_{ 2 } }{ \longrightarrow } \underset { 1-Iodobutene }{ { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }I } \) 
(ii) \({ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }Cl+Nal\overset { Acetone }{ \longrightarrow } { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }I+Nacl\) 
(iii) 

(i) DDT is used to control certain insects which carries diseases like malaria and yellow fever.
(il) It is used in farms to control some agricultural pests.
(iii) It is used in building construction as pest control agent.
(iv) It is used to kill certain kind of insects like housefly and mosquitoes due to its high and specific toxicity.

(i) DDT is p, p' -dichloro-diphenyl-trichloroethane
(ii) DDT can be prepared by heating a mixture of chloro benzene with chloral in the presence of conc.H₂SO₄
(iii) 

(i) Freons are used as refrigerants in refrigerators and air conditioners.
(ii) It is used as a propellant for foams and aerosols.
(iii) It is used as a propellant for foams to spray out deodorants, shaving creams and insecticides.