Question

Account for the following: 1)Halo alkanes have gher boiling point than the corresponding parent alkane. 2)Boiling point of halo alkanes RIRBrRCl RF 3)Boiling point of 1-Bromo butane 2-Bromo butane 1-Bromo- 2-methylpropane 2-Bromo- 2-methyl propane. 4)Melting point of p-Dichlo benzene is gher than its ortho and meta isomer. 5)Halo alkanes are polar in nature but sparingly soluble in water. 6)Iodo alkane can not be prepared by the reaction of alcohol with KI and sulphuric acid. Phosphoric acid is used in place of sulphuric acid. 7)Order of reactivity of alcohol with HX is tert alcohol sec alcohol primary alcohol.. 8)Halo arenes can not be prepared by treating phenol with HX or NaX in the presence of sulphuric acid. 9)Iodination of benzene is carried out in the presence of O3or HNO3. 10)Propane on chlorination gives 2-chloro propane as a major product and not 1-chloro propane. 11)Kharasch effect is possible only with HBr and not with HCl and . 12)Alcohol reacts with th

Answer 1

1) higher molecular weight results in higher boiling point, 2) RI>RBR>RCl>RF, reason same as 1. 3)As more branching result in lower surface area.4)it is due to higher crystal symmetry in para compound that ortho and meta one.5)As they cannot form hydrogen bond with water.6)In the presence of sulphuric acid KI produces HI which is changed to I2 as sulphuric acid is oxidising agent.So reaction cannot occur and phosphoric acid has to be used.7) As in presence of HX carbocation is formed from alcohol leaving water and stability of tertiary carbocation is higher than secondary and primary.8)Same as due to oxidation by sulfuric acid.9)As iodine does not serve as a base like other halogen and it needs to be oxidised by acid to I+.10) As secondary or tertiary carbocation is more stable than primary.11)It is due to the fact that in presence of peroxide radical reacton happens which is expthermic in case of only HBr.