12 chemistry impq_ch10_haloalkanes_and_haloarenes_01

103 XII – Chemistry
AK
Unit - 10
HALOALKANES AND HALOARENES
1. Write the IUPAC names of the following compounds.
(i)
(ii)
(iii)
(iv)
(v) CH2Br – CH = CH – CH2 – C  CH
(vi)
(vii)
(ix) (CCl3)3 CCl
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2. Write the structure of following halogen compounds
(i) 2-chloro-3-methylpentane
(ii) 2-(2-chlorophenyl)-1-iodooctane
(iii) 1-bromo-4-sec-butyl-2–methylebenzene.
(iv) p-bromotoluene.
(v) chlorophenylmethane
3. Arrange the following in the increasing order of properly indicated :
(i) bromomethane, chloromethane, dichloromethane. (Increasing order
of boiling points).
(ii) 1-chloropropane, isopropyl chloride, 1-chlorobutane (Increasing order
of boiling point)
(iii) dichloromethane, chloroform, carbon terachloride. (Increasing order
of dipole moment.
(iv) CH3F, CH3Cl, CH3Br, CH3l (Increasing reactivity towards nucleophilic
substitution and increasing order of dipole moment)
(v) o,m.p-dichlorobenzenes (Increasing order of melting points).
4. Complete the following reactions :
(i)
(ii) CH3 – CH2 – Cl + Ag NO2
→

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5. How will you bring about the following conversions?
(i) benzene to 3-bromonitrobenzene
(ii) ethanol to but-1-yne
(iii) 1-bromopropane to 2-bromopropane
(iv) benzene to 4-bromo-1-nitrobenzene
(v) aniline to chlorobenzene
(vi) 2-methyl-1-propene to 2-chloro-2-methylpropane
(vii) ethyl chloride to propanoic acid
(viii) but-1-ene to n-butyl iodide
(ix) benzene to phenylchloromethane.
(x) tert-butyl bromide to isobutyl bromide.
6. Identify the products formed in the following sequence :
(i)

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(viii) CH3Br KCN
→ A
+
3H O
→
4Li Al H
ether
→
7. Explain the following reactions with suitable example :
(i) Finkelstein reaction.
(ii) Swarts reaction.
(iii) Wurtz reaction.
(iv) Wurtz-Fitting reaction
(v) Friedel-Craft’s alkylation reaction.
(vi) Friedel-Craft’s acylation reaction
(vii) Sandmeyer reaction.
8. Write the major products and name the rule responsible for the formation
of the product.
9. Write the difference between
(i) enantiomers and diastereomers
(ii) retention and inversion of configuration.
(iii) electrophilic and nucleophilic substitution reactions.
10. Give a chemical test to distinguish between the following pairs of
compounds:
(i) chlorobenzene and cyclohexylchloride.
(ii) vinyl chloride and ethyl chloride.
(iii) n-propyl bromide and isopropyl bromide.
11. Give mechanism of the following reactions :
(i) (CH3)3C – Cl + O
–
H → (CH3)3 C – OH
(ii) CH3 – Cl + OH– → CH3 – OH

AK
12. Which compound in each of the following pairs will react faster in SN2
reaction with OH– and why?
(i) CH3Br or CH3I
(ii) (CH3)3 CCl or CH3Cl
13. In the following pairs which halogen compound undergoes faster SN1
reaction?
(i)
(ii)
(iii) (CH3)3C – Cl and C6H5CH2Cl
(iv) C6H5CH2Cl and C6H5C(Cl)C6H5
(v) CH2 = CH – Cl and CH2 = CH – CH2Cl
14. Give reasons for the following :
(i) The bond length of C–Cl bond is larger in haloalkanes than that in
haloarenes.
(ii) Although alkyl halides are polar in nature but are not soluble in
water.

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(iii) tert-butyl bromide has lower boiling point than n-Butyl bromide.
(iv) haloalkanes react with KCN to form alkyl cyanide as main product
while with AgCN alkyl isocyanide is the main product.
(v) sulphuric acid is not used in the reaction of alcohol with Kl.
(vi) thionyl chloride is the preferred reagent for converting ethanol to
chloroethane.
(vii) haloalkanes undergo nucleophilic substitution reaction easily but
haloarenes do not undergo nucleophilic substitution under ordinary
conditions.
(viii) chlorobenzene on reaction with fuming sulphuric acid gives ortho
and para chlorosulphonic acids.
(ix) 2, 4-dinitro chlorobenzene is much more reactive than chlorobenzene
towards hydrolysis reaction with NaOH.
(x) Grignard reagent should be prepared under anhydrous conditions.
(xi) the dipole moment of chlorobenzene is lower than that of cyclohexyl
chloride.
(xii) neopentyl bromide undergoes nucleophilic substitution reactions very
slowly
(xiii) vinyl chloride is unreactive in nucleophilic substitution reaction.
(xiv) An optically inactive product is obtained after the hydrolysis of
optically active 2- bromobutane.
[Hint : The hydrolysis reaction occurs by SN1 pathway. The carbocation
is formed first which gives a mixture of (±) butan-2-ol in the second step].
(xv) methyl iodide is hydrolysed at faster rate than methyl chloride.

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15. Write the different products and their number formed by the
monochlorination of following compounds :
(i) CH3CH2CH2CH3
(ii) (CH3)2CHCH2CH3
(iii) (CH3)2CHCH(CH3)2
[Hint : (i) Two, (ii) four, (iii) three
16. (a) When 3-methylbutan-2-ol is treated with HBr, the following reaction
takes places :
Give the mechanism for this reaction.
(b) In the following reaction :
major and minor products are :
(i) (ii)
(iii) (iv)
Ans. Major (iii) minor (i)
17. Give one use of each of following :
(i) Freon-12 (ii) DDT
(iii) Carbon tetrachloride (iv) Iodoform

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18. An optically active compound having molecular formula C7H15Br reacts
with aqueous KOH to give C7H15OH, which is optically inactive. Give
mechanism for the reaction.
A racemic mixture is obtained which is optically inactive.]
19. An organic compound C8H9Br has three isomers A, B and C. A is optically
active. Both A and B gave the white precipitate when warmed with alcoholic
AgNO3 solution in alkaline medium. Benzoic acid, terephthalic and p-
bromobenzoic acid were obtained on oxidation of A, B and C respectively.
Identify A, B and C.
*20. An alkyl halide X having molecular formula C6H13Cl on treatment with
potassium tert-butoxide gives two isomeric alkenes Y and Z but alkene y
is symetrical. Both alkenes on hydrogenation give 2, 3-dimethylbutane.
Identify X, Y and Z.

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*21. An organic compound (A) having molecular formula C3H7Cl on reaction
with alcoholic solution of KCN gives compound B. The compound B on
hydrolysis with dilute HCl gives compound C. C on reduction with
H2/ Ni gives 1-aminobutane. Identify A, B and C.
[Ans. : (A) CH3CH2CH2Cl, (B) CH3CH2CH2CN, (C) CH3CH2CH2CONH2
*22. Identify A, B, C, D, E, R and R´ in the following sequence of reactions :
23. Which nomenclature is not occording to IUPAC system.
(i) Br – CH2 CH = CH2; 1–bromoprop-2-ene
(ii) 4–bromo-2, 4-dimethylhexane
(iii) , 2–methyl–3–phenylpentane
(iv) , 5–oxohexanoic acid
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12 chemistry impq_ch10_haloalkanes_and_haloarenes_01

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