Haloalkanes and haloarenes class 12 chemistry important questions for cbse examination

                    Class 12 chapter 10 cbse important questions 


1. Out of chlorobenzene and cyclohexyl chloride which one is more reactive towards nucleophilic  substitution reaction and why ?  CBSE 2019 

Answer : it is due to resonance the c-cl bond in chlorobenzene having partial double bond character which makes the substitution of chlorine more difficult in chlorobenzene than in cyclohexyl chloride where the c-cl bond has pure single bond character .

2. Why is t-butyl bromide more reactive towards sn1 reaction as compare to n-butyl bromide ?cbse 19 
answer : due to higher stability of tertiary carbocation then n-butyl bromide 

3. why chloroform is stored in dark coloured bottles completely filled so that air is kept out ? CBSE 2110 
Answer: because chloroform is slowly oxides by air and formed poisonous gas phosgene 
              2CHCl3 +O2 >>>>>  2COCl2 +2HCL 

4. Thionyl chloride method is preferred for preparation of alkyl chloride from alcohols? cbse 2019
Answer ; because in this methos SO2 and HCl gas being to formed during the reaction and it is easily escape into the atmosphere and alkyl chloride is most pure sate in the vessels .

5. Difference between retention and inversion ? 
 Answer : if the relative configuration of atoms / groups are the same after the reaction of chiral centre molecule then that compound is called retention of configurations . 
if the relative configuration of atoms / groups are change after the reaction of chiral Centre molecule then that compound is called inversion  of configurations . which is opposite to the that reactant . 

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