Download Give reasons for the following.(one mark each)

HALOALKANES AND HALOARENES.
(Previous board questions only)
Give reasons for the following.(one mark each)
1. Reaction of alcohol with thionyl chloride is the best preferred method for the
preparation of alkyl halides.
2. Free radical chlorination or bromination of alkanes is not preferred for the preparation of alkyl
halides.
3. Aryl fluorides are not prepared by the electrophilic substitution of arenes.
4. Reaction of toluene with iodine requires an oxidizing agent.
5. Sulphuric acid is not used for the reaction of alcohol with KI.
6. Boiling point of alkyl halides are higher than that of corresponding hydrocarbons.
7. Boiling point decreases in the order RI> RBr> RCl> RF.
8. Boiling point of isomeric alkyl halides decreases with increase in branching.
9. Para-dihalobenzene has higher melting point than ortho and meta.
10. Haloalkanes are only slightly soluble in water but tends to dissolve better in organic solvents.
11. CN- and NO2- are considered as ambident nucleophiles.
12. Aklyl halides give alkyl cyanides on reaction with KCN and alkyl isocyanides on reaction with
AgCN.
13. SN2 reaction always proceeds with inversion of configuration.
14. The order of reactivity of alkyl halides for SN2 is 1o> 2o>3o
15. The order of reactivity of alkyl halides for SN1 is 3o> 2o>1o
16. Even trace amounts of water has to be removed from Grignards reagent .
17. Haloarenes/ aryl halides are less reactive towards nucleophilic substitution reactions when
compared to alkyl halides. OR
18. [alkyl halides undergo hydrolysis more easily as compared to aryl halides]
19. Nitro group attached to benzene ring shows its activity only at ortho & para position and not at
meta positions.
20. Electrophilic substitution reaction in haloarenes occurs slowly and require drastic
conditions as compared to those in benzene.
21. Allylic and benzylic halides are more reactive towards nucleophilic substitution .
22. Allyl chloride is more reactive than n-propyl chloride towards nucleophilic substitution.
23. Neo-pentyl chloride do not follow SN2 reacion.
24. Grignard’s reagent should be prepared under anhydrous condition.
25. Dipolemoment of chlorobenzene is lower than that of cyclohexyl chloride.
26. Use of DDT is banned .
27. Tertiary alcohols react much faster than secondary & primary with lucas reagent.
28. Optically active 2-iodobutane on treatment with NaI in acetone gives a product which does not
show optical activity.
29. Vinyl chloride is hydrolysed more slowly than ethyl chloride.
30. Boiling point of alkyl bromide is higher than that of alkyl chloride.
31. Alkyl halides are better solvents than aryl halides.
32. Haloalkanes used as solvents in industry are chloro compounds rather than bromo
compounds.
33. Small amount of ethyl alcohol is added to chloroform bottle.
34. P-nitrochlorobenzene undergoes nucleophilic substitution faster than chlorobenzene.
35. Name the following
a) Name the antibiotic containing chlorine
b) Name the haloalkane possessing antiseptic properties.
c) Halogenated compound that can be used as potential blood substitutes.
d) Synthetic halogen used in the treatment of malaria.
e) Name the chlorine containing compounds damaging the ozone layer.
36.Rearrange in the increasing order of reactivity towards SN2 and SN1.
a) 1- Bromobutane, 1-Bromo-2,2-dimethylpropane, 1-Bromo-2-methylbutane.
b) 3-Bromo-2-methylbutane, 2-Bromo-2-methylbutane, 1-Bromo-3-methylbutane.
c) 2-Bromo-2-methylbutane, 1- Bromopentane, 2- Bromopentane
37.Distinguish between
a)
b)
c)
d)
Chloroform and carbon tetrachloride.
Ethanol and propan-2-ol.
2-Methylpropan-2-ol and propan-1-ol.
Chlorobenzene and benzylchloride.
PRACTICE QUESTIONS(one mark each)
1. Give the IUPAC name of
2. Give the structure of 4-Bromo-3-methylpent-2-ene.
3. Which is easily hydrolysed by aq.KOH and why?
4. Which undergoes SN2 reaction faster.
5. Complete the following.