CPP

IIT-JEE
CPP Class - XII

ALKYL AND ARYL HALIDE

NOMENCLATURE AND PREPARATION

1. Give a suitable IUPAC name for each of the following structures :

(a) Br Br (b) Cl

2.

3.

EE(CCl3)2C=CH2 + HCl

(A) Me2CH—CH2Cl
O
||
O
||
CH3  CO O  C CH3
        
(B) MeCH2—CH(Cl)Me
. What is A?

Halogenation of hydrocarbons in presence of light, involves

(A) free radicals (B) carbocations
(C) (CCl3)2CHCH2Cl

(C) carbanions
(D) none

(D) none
TJ
4. In the addition of halogens to alkenes, alkene acts as an,
(A) electrophile (B) leaving group (C) nucleophile (D) solvent

5. The order of polarity of CH3I, CHBr and CH3Cl molecules follows the order:
(A) CH3Br  CH3Cl  CH3I (B) CH3I  CH3Br  CH3Cl (C) CH3Cl  CH3Br  CH3I (D) CH3Cl  CH3I  CH3Br

6. Which of the following leads to the formation of an alkyl haldie ?

FII
2 Re dP Br 2 SOCl
(A) C2H5 OH  (B) C2H5 OH 

2 KBr Conc,H SO
4
(C) C2H5 OH  (D) All of these

7. Which reaction is termed as Darzen’s reaction ?

(A) ROH + HCl (B) ROH + PCl5 (C) ROH + SOCl2 (D) ROH + PCl3

8. Acetaldehyde reacts with PCl5, to give :

(A) ethyl chloride (B) ethylene chloride (C) ethylidene dichloride (D) trichloroacetaldehyde

9. Benzene reacts with Cl2 in the presence of FeCl3 to form :

(A) benzyl chloride (B) benzal chloride (C) chlorobenzene (D) benzenehexa chloride

10. Benzyl chloride can be prepared by reacting :

(A) Toluene with Cl2 in the presence of FeCl3 (B) Benzene with CH3Cl in the presence of AlCl3
(C) Toluene with Cl2 in the presence of sunlight (D) Benzene with Cl2 in the presence of FeCl3

FIITJEE 1
 CONCEPT BASED APPLICATION

11. Racemization in SN1 reactions is mainly due to :

(A) Solvent effects (B) Nucleophile (C) Carbocation formation (D) Carbanions

12. The nucleophilicity of halogens in polar protic solvent follows the order :
(A) I– > Cl– > Br– > F– (B) I– > Br– > Cl– > F–
– – – –
(C) I < Br < Cl < F (D) Br– > I– > Cl– < F–

13. Inversion of configuration is observed when the reaction proceeds through :

(A) SN1 mechanism (B) E2 mechanism (C) SN2 mechanism (D) Rearrangement

14. CH3COO– is a bad leaving group because it is a :

(A) Strong base (B) Weak base (C) Conjugate base (D) Solvent

15. Which one of the following compounds most readily undergoes substitution by SN2 mechanism ?
CH3 CH3

EE
(A) CH3 CH CH2Cl (B) CH3CH2Cl (C) CH3 CH Cl (D) CH3 C Cl
C3H7 CH3

16. Being a primary alcohol, neopentyl alcohol, doesn’t undergo substitution through SN2 mechanism, due to :
(A) steric hindrance (B) solvent effects (C) poor leaving group (D) High molecular weight

17. The nature of nucleophile doesn’t alter the rate of SN1 reaction because :
(A) Nucleophiles are not used
(B) Concentration of nucleophile is less
(C) Nucleophiles are not involved in rate determining step
TJ
(D) All the above
18. SN1 mechanism will be readily shown by :
Cl
(A) CH3—CH2Cl (B) CH3 CH CH3 (C) CH3 CH CH CH3 (D) CH3Cl
CH3 Cl
19. The carbon in the reactive intermediate of SN1 is in the hybridization :
(A) sp3 (B) sp2
FII
(C) sp (D) Depends upon the nucleophile
20. An alkyl halide may be converted into an alcohol by
(A) Addition (B) Substitution (C) Dehydrohalogenation (D) Elimination

SUBSTITUTION AND ELIMINATION

21. In the reaction
CH3CC–Na+ + (CH3)2CHCl  ? the product formed is
(A) 4-methyl-2-pentyne (B) propyne (C) propyne and propene (D) none

22. Butane nitrile may be prepared by heating:

(A) Propyl alcohol with KCN (B) Butyl alcohol with KCN
(C) Butyl chloride with KCN (D) Propyl chloride with KCN

23. A; ‘A’ is :

(A) Ph—CO—CMe3 (B) Ph—CH 2—CMe3 (C) Ph—CMe3 (D) None

24. The reaction between ethyl alcohol and methyl magnesium bromide gives
(A) CH4 (B) C2H6 (C) C3H8 (D) None

FIITJEE 2
25. OH
A  ; What is A?
H2O
N
H
(A) (B)
N N
H
(C) CH3—NH—CH2CH2Br (D) NH2CH2CH2CH2CH2—Br

26. Order of hydrolysis of the following Compound in increasing order is:

Br Br Br (CH 3 ) 3 CBr

(I) (II) (III) (IV )

(A) I < II < III < IV (B) I < IV < II < III (C) IV < III < II < I (D) I < II < IV < III

27. Which of the following cannot undergo nucleophilic substitution under ordinary condition?
(A) allyl chloride (B) benzyl chloride (C) n-propyl chloride (D) vinyl chloride

AlCl3, 
28. (CH3)3 CCH2Cl X (predominant), X is
(A) (CH3)2 C CH2 CH3 (B) CH3 CH2 CH CH2 CH3
|
|
Cl
Cl
(C) CH3 CH2 CH2 CH2 CH2 Cl (D) none of the above.

Me Me Me
- -
HO HO
29. HO H H Cl B + H OH
(II) (I)

Et Et Et

(B) (A)
steps I and II are
(A) both SN1 (B) both SN2 (C) I: SN1, II: SN2 (D) I: SN2, II: SN1

30. Major product of the following SN1 reaction is

_
CH3 – CH – CH – CH3 + O C2H5 
| |
Br CH
3
(A) CH3 – CH  CH – CH3 (B) CH3 – CH  CH2 CH2 OC2H5
| | |
OC2H5 CH3 CH3
CH3
|
(C) CH3 CH2 C CH 3 (D) none is correct.
|
OC2H5

31. Cl CH2 CH2 CH2 – I + KCN  P (major), P is

(A) NC – CH2 CH2 CH2 – I (B) Cl – CH2 – CH2 CH2 CN
(C) CH2 = CH CH2 I (D) Cl CH2 CH = CH2

FIITJEE 3
32.
Br2 / H2O
CH2 A, A is

CH2Br CH2OH
(A) (B)

OH Br
CH2 Br CH3
(C) (D)

Br OH

33. Which of the following is most rapidly hydrolysed by SN1 mechanism?

(A) CH3 CH = CH Cl (B) Cl CH2 CH = CH2

(C) CH2Cl (D) (C6H5)3CCl

34. Which reagent(s) could be used to carry out the following reaction ?

Br

(A) NBS/CCl4
(B) NBS/CCl4, then Br2/hv
(C) Br2/hv, then (CH3)3COK/(CH3)3COH, then NBS/CCl4
(D) (CH3)3COK/(CH3)3COH, then NBS/CCl4

35. In which of the following case, rate of nucleophilic substitution will be fast
(A) t-butyl chloride (B) triphenylmethyl chloride
(C) triphenylmethyl bromide (D) equal in all cases

36. The structures of two 3°-bicyclic chlorides (I and II) are shown below.

Which of the following statements is correct?

(A) on treatment with KOH in ethanol, both compounds undergo E2 elimination.
(B) on treatment with KOH in ethanol, I undergoes substitution and II undergoes elimination.
(C) I is more reactive than II for both substitution and elimination
(D) II is more reactive than I for both substitution and elimination

37. Which of the following will not react by unimolecular nucleophilic substitution mechanism?
CH3
(A)  C2 H 5 3 C Br I
(B) C2H5 (C) CH Br (D)

Br

FIITJEE 4
 Comprehension

R-X will react in two ways with a base. Some times it undergoes elimination reactions (E1, E2, E1CB) and some
times substitution reactions (SN1 , SN 2  etc.) . Depending upon the given substrate, reagent and solvent one can
decide which reaction is more feasible.

38. With which mechanism following reaction might have happened?

NEt2
H H H
Et2NH
C C  C C One of the products
D C Cl H
D C CH3
CH3
H H
(A) SN1 (B) SN2 (C) SNi (D) either SN1 or SN2

39. With which mechanism following reaction might have happened?

Cl OH
H2O + (CH3)2 CO( 80% )

CH3 CH3

(A) SN1 (B) E1CB 

(C) SN2 allylic S
N2  (D) SN2

40. 2-bromopentane is heated with potassium ethoxide in ethanol. The major product is
(A) Trans - pent-2-ene (B) 2-ethoxy pentane (C) Pent-1-ene (D) cis-pent-2-ene

41. If an alkyl halide CH3CH2CH2X goes for dehydrohalogenation followed by addition of HX will lead to
formation of
(A) Same alkyl halide (B) Different (C) An isomer (D) An hydrocarbon

CH3
|

42. CH3 – C Cl + C2H5ONa   Major product of this reaction is
|
CH3
CH3
|
(A) CH3 – C OC2H5 (B) CH3 – C  CH2
| |
CH3 CH
3

(C) CH3 – CH – CH2 OC2H5 (D) none is correct.

|
CH
3

43. With which mechanism following reaction might have happened?

H -
OH, 
CH CH 2 C CH CH C H
O O
OH

(A) SN1 (B) E1CB 

(C) SN2 allylic S
N2  (D) SN2

FIITJEE 5
 CH3
44. C 2H5 OH
H3C   Y

CH3 Br
Y would be
CH3 H3C
(A) H3C (B)
CH3 O C2H5 H3C CH3
CH3 CH3
(C) H3C (D) H3C
CH3 O H
O CH3
C2 H 5

CH3
-
45. H3C O K
H3C
CH3
Br
Z would be
H3C CH3
CH3
(A) CH2 (B)
H3C O
CH3
OCMe3
(C) H3C (D) None
CH3
MISCELLANEOUS

46. Phosgene is a common name for

(A) CO2 and pH3 (B) Phosphoryl chloride (C) Carbonyl chloride (D) Carbonyl tetrahcloride

47. Gem dihalide on hydrolysis gives

(A) Carboxylic acid (B) Aldehyde (C) Ketone (D) B or C

48. Which one is correct

(A) Freon -14 is CF4, Freon-13 cis CF3Cl. Freon -12 is CF2Cl2, Freon-11 is CFCl3
(B) Freons are chlorofluoro carbons
(C) Freons are used as refrigerants
(D) All

49. Iodoform test will not be given by

(A) Acetaldehyde (B) Acetone (C) 2-pentanone (D) 3-pentanone

50. Cl Cl
Na P
Dry ether

Cl Cl
The product P is :

(A) (B) (C) (D)

Conc. H2SO4
51. Chloral + Cl product. The product is :

(A) Lindane (B) DDT (C) Teflon (D) Ethaneperchlorate

FIITJEE 6
 GRIGNARD’S REAGENT

52. In the given reaction

PhMgBr + D2O  (X) : (X) will be :
(A) (B) (C) (D)

53. Find the product of the following reaction

CH3CH2MgBr + HgCl2  (X) ; (X) will be :
(A) (CH3CH2)2Hg (B) CH3CH3 (C) CH3CH2Cl (D) CH3CH2HgCl

54.

Identify the structure of product :

(A) (B) (C) (D)

55. Find the product of the following reaction

Find out ‘B’ :

Br

(A) HO—H2C—CH2—CH2—Br (B) HO—CH2—CH—CH3

(C) HO—H2 C—CH CH2 (D) Br Mg CH2—CH CH2

56.

(A) (B)

(C) (D)

57. Find the product of the following reaction,

Find out the final product (C) :

(A) (B) (C) (D) None of these

58.

(A) (B) (C) (D)

FIITJEE 7
59.

The final product of the reaction is

(A) (B) (C) (D)

60.

Find the structure of product :

(A) (B) (C) (D)

61.

Identify (P) :

(A) (B) (C) (D)

ARYL HALIDE
Cl

62. Br
NaOC H
 2
5
X

O 2N NO 2

Here X is
Cl
O C 2H 5

OC2H5
(A) (B)

O2N NO2 O 2N NO2

OC2H5
Br
(C) (D) None
O2N NO2

FIITJEE 8
63.

(A) (B) (C) (D) None of these

64.

(A) (I) is more reactive than (II) (B) (II) is more reactive than (I)
(C) (I) and (II) have same reactivity (D) none of these

FIITJEE 9
65.

(A) (B)

(C) (D) none of these

EE
66.

(A) (B)
TJ
(C) (D)
FII
67.

(A) (B)

(C) (D)

FIITJEE 10
68.

(A) (B)

(C) (D)

EE
69.

(A) (B) (C) (D)

TJ
70.
FII
(A) (B)

(C) (D)

Short answer questions

SECTION - I
71. Explain the formation of the products in the following reaction :
CH3 H3C
H3 C Cl
+ H2O CH2 +
+ Ag OH
H3C OH H3 C
CH3
85% 15%

FIITJEE 11
72. (a) Arrange the following alkyl bromides in order of decreasing reactivity towards iodide ion in dry acetone.
H3C CH3 H3C CH3
H3C Br , , and H3C Br
Br H3C Br
CH3
CH3 Cl
H3C , H3C Br , H3C and H3C
(b)
Br Cl Cl

73. Offer an explanation for the following observations :

(a) Dichlorobenzene has a net dipole moment of zero
(b) Vinyl chloride is unreactive in nucleophilic substitution reactions.
(c) Chlorobenzene has a lower dipole moment than methyl chloride.
(d) Alkyl halides, though polar, are insoluble in water.
(e) Benzyl bromide is more reactive than cyclohexyl bromoethane with aqueous NaOH
(f) CH3CH2I is more reactive than CH3CH2Cl towards KCN
CH3
(g) H3C is very unreactive toward nucleophiles.
Cl

EE
H

74. On a potential energy diagram show the course of meta and para nitration of chlorobenzene.

75. Trans-2-butene is obtained as the major product on dehydrobromination of 2-bromobutane.

76. Which of the isomer in the following pair will eliminate faster in the presence of base ? Write the structure of the
product.
Br H H H
CH3 CH3
CH3 C C CH23 C C
(i) (ii)
TJ
CH3 CH3
Br

77. Draw the structures of the major monohalo product in each of the following reactions :
OH
OH heat
(a) + SOCl2  (b) + HCl 
FII
HO
acetone
(c) CH3CH2Br + NaI 
reflux
 (d) CH3CH2Br + Hg2F2 

78. Give the structures of the main organic substitution product expected from the reaction of 1-bromobutane with
(a) LiAlH4
(b) C6H5ONa

79. Write the structures of the major organic product formed in each of the following reactions:
aq. ethanol C 2 H5 ONa
(A) CH3CH2Br + KCN  (B) (CH3)2CH–CH(Br)CH2CH3 
ethanol / heat


heat Liq.NH
(C) CH3CH2Cl + SbF3   3
(C) CH2=CHCH2Br + CH3CCNa  

peroxide
(E) CH3CH2CH=CH2 + HBr  

80. An alkyl halide (A), on reation with magnesium in dry ether followed by treatment with ethanol gave 2-methylbutane.
Write all the possible structures of A.

FIITJEE 12
 SECTION - II
81. Explain why p-dichlorobenzene has higher melting point and lower solubility than those of o and m isomers.

82. Explain why thionyl chloride method is preferred for preparing alkyl chloride from alcohols.

83. Describe the method for the preparation of haloarenes from diazonium salts.

84. The following chlorides undergo solvolysis in the following order. Explain.
(C6H5)3CCl3 > (C6H5)2CHCl > C6H5CHClCH3 > C6H5CH2Cl

85. Compare the reactivity of following in SN2 reactions:

1-chlorobutane, 1-chloro-1-butene and 1-chloro-2-butene

86. RCl is hydrolysed to ROH slowly but the reaction is rapid if a catalytic amount of KI is added to the reaction
mixture.

EE
87. What is the product ?
CH3CH2Br 
Mg ether phenol
  Product

88. The following reaction is pH dependent.

90% aqueous
R—Br 
acetone
 ROH + HBr
R = –C2H5, –CH(CH3)2, –C(CH3)3
It was found that an increase in hydroxide ion concentration causes a corresponding increase in the rate of the
reactant when R = –C2H5 but not when R = –C(CH3)3, explain.
TJ
True/ False

89. Chloroform gives carbylamine reaction with primary amines.

90. R—OH reacts with NaBr in presence of H2SO4 to give R—Br.

FII
91. AgCN reacts with R—X to form R—CN as the major product.

92. 1,3-butadiene with bromine in molar ratio generates predominantly 1,4-dibromobut-2-ene

93. Z; Z=

*****

FIITJEE 13
 ALKYL HALIDE ANSWER KEY
Nomenclature and Preparation

3 1
2
Br Br 4 Cl
1. (a) (b)
6 5
2 4
1 3 5 6
2,2-dibromo-4-cyclopropylhexane 1-chloro-4-isopropyl-5-methylhexane

2. (C) 3. (A) 4. (C) 5. (C) 6. (D) 7. (C) 8. (C) 9. (C) 10. (C)

Concept based application

11. (C) 12. (B) 13. (C) 14. (A) 15. (B) 16. (A) 17. (C) 18. (C) 19. (B) 20. (B)

Substitution and Elimination

21. (A) 22. (D) 23. (C) 24. (A) 25. (D) 26. (D) 27. (D) 28. (A) 29. (C) 30. (C) 31. (B)

EE
32. (A) 33. (D) 34. (C) 35. (C) 36. (D) 37. (D) 38. (D) 39. (A) 40. (A) 41. (C) 42. (B)
43. (B) 44. (B) 45. (A)

Miscellaneous

46. (C) 47. (D) 48. (D) 49. (D) 50. (D) 51. (B)

Grignard’s Reagent

52. (D) 53. (A)0 54. (A) 55. (A) 56. (B) 57. (B) 58. (D) 59. (B) 60. (A) 61. (C)
TJ
Aryl Halide

62. (A) 63. (B) 64. (A) 65. (C) 66. (A) 67. (A) 68. (C) 69. (A) 70. (D)

Short Answer Type Questions

71. Both products are derived from the allylic cation which has two resonance forms and the product can be formed
FII
by attack of water at either electron deficient carbon. The major product (85%) is formed from the most stable
tertiary and allylic carbon.

72. (a) CH3Br > CH3CH2Br > (CH3)2CHBr > (CH3)3CBr

CH3
CH3 Cl
(b) H3C < H3C < H3C < H3C Br
Cl CH3 Br

73. (a) In Cl Cl the two individual dipoles cancel each other..

(b) Vinyl cation is not formed readily. The carbon chloride bond of vinyl chloride is shorter and stronger due to
two reasons:
(1) The carbon bearing the halide is sp2 hybridized and thus the electrons of carbon orbitals are closer to
the nucleus than those of an sp3 hybridized carbon.
(2) Resonance of the type shown here strengthens the carbon-halogen bond by giving it a double bond
character.
 +
RCH CH X R CH CH X
Thus a stronger carbon-halogen bond means that bond breaking by either an SN1 or SN2 mechanism will
require more energy.

FIITJEE 14
 (c) The value of dipole moment of chlorobenzene is lower than that of methyl chloride. The difference is
attributed to two factors – first the lone-pair on the chlorine atom overlaps the -orbital of the benzene ring
and secondly because C–Cl bond in chlorobenzene may be represented as

Cl H3C Cl

Csp2 –Clp while in methyl chloride as Csp3 –Clp. Therefore, the higher ‘s’ character of the benzene carbon
atom makes it electron-withdrawing which lowers the dipole moment.
(d) Alkyl halides do not form hydrogen-bond with water.
(e) The benzyl cation is stabilized by resonance.
(f) Iodide ion is a better leaving group.
(g) Steric hindrance to SN2 attack.

Cl
74. meta


NO2
para
H
Potential energy

Cl

EE
Cl H NO2

+ NO2

Reaction coordinate
The Cl group is ortho- and para-directing. The ring is thus activated towards nitration at these positions but
deactivated at the meta-position.

75. The -hydrogen and the leaving group in 2-bromobutane can assume an anti-periplanar conformation in two
ways:
TJ
B B
H H
CH3 H CH3 H

CH3 H H CH3
Br Br
Gauche Anti
FII
–Br– –Br–

CH3 H CH3 H
+ BH +
+ BH+
CH3 H H CH3

cis-2-Butene trans-2-Butene
The gauche conformation of 2-bromobutane has more energy (hence less stable) than anti-conformation due to
torsional strain. So major product is obtained from anti-conformation as trans-2-butene.

76. Ist because tertiary benzylic carbocation is more stable and the product is
CH3
CH3 C C
CH3

OH Cl
77. (a) + SOCl2  + SO2 + HCl

(b) Due to resonance, C–O bond in phenols is much stronger than C–O bond in alcohols and hence substitution
occurs only at the alcoholic group.

FIITJEE 15
 OH heat
Cl
+ HCl  + H 2O
HO HO
acetone, reflux
(c) CH3CH2Br + NaI  CH3CH2I + NaBr
(Finkelstein reaction)

Halogen exchange
(d) 2CH3CH2Br + Hg2F2   2CH3CH2F + Hg2Cl2
(Swarts reaction)

78. (a) LiAlH4 + 4CH3CH2CH2CH2Br  4CH3CH2CH2CH3 + LiBr + AlBr3

Williamson's
(b) C2H5O–Na+ + CH 3CH2CH2 Br 
synthesis
 CH 2 CH 2 CH 2 CH 2 –O–C2 H5 + NaBr
Butyl ethyl ether

79. (a) CH3CH2CN (b) (CH3)2C=CHCH2CH3

(c) CH3CH2F (d) CH2=CHCH2CCCH3
(e) CH3CH2CH2CH2Br

80. Write all the possible alkyl halides obtained by monohalogenation of 2-methylbutane.
CH3

EE
CH 3 Br CH3 Br CH 3 , H3C Br
, Br ,
CH 3 CH3 CH 3 H3C CH 3
The Grignard reagents of all these four alkyl halides will give 2-methylbutane on treatment with ethanol.

SECTION - II
81. The p-isomer being more symmetrical fits closely in the crystal lattice and thus has stronger intermolecular
force of attraction then ortho and meta isomers. Since during melting of dissolution, the crystal lattice breaks
therefore, a larger amount of energy is needed to melt or dissolve than p-isomers than the corresponding o and
m isomers.
TJ
82. Because the byproducts of the reaction i.e., SO2 and HCl being gases escape into the atmosphere leaving
behind alkyl chlorides in almost pure state.

83. By treatment with CuCl/HCl or HBr/CuBr (Sandmeyer reaction) or treatment of diazonium salts with KI in
presence of Cu powder. (Gattermann method)
CuCl/HCl
C6H5N2Cl 
CuBr/HBr
 C6H5X (X = Cl, Br or I)
or
KI+Cu powder
Fluorobenzene is however, prepared by Balz-scheimann reaction as follows:
FII
HBF 
C6H5N2Cl  4
-HCl
 C6H5N2BF4   C6H5F + N2 + BF3

84. Because this is the order of stability of carbocations formed after the cleavage of the C—Cl bond.

85. The reactivity of 1-chloro-2-butene > 1-chlorobutane > 1-chloro-1-butene in SN2 displacement.

86. Iodide ion is a powerful nucleophile and hence reacts rapidly with RCl to form RI.

KI  K+ + I– ; I– + R Cl  R—I – + Cl
–
–
Further because I ion is a better leaving group than Cl ion, therefore, RI is more rapidly hydrolysed than RCl to
form ROH,
R—I + OH–  R—OH + I–
–
The I ion thus regenerated recycles in the above reaction thereby explaining its catalytic effect.

Mg Phenol
87. CH3CH2Br 
Ether
 CH3CH2MgBr  CH3 CH 3
(Product)

88. This simply shows that the reaction of C2H5Br and (CH3)3CBr is proceeding by two different mechanisms; first
one is SN2 and second reaction via SN1.

True / False

89. True 90. True 91. False 92. True 93. True

FIITJEE 16

NCERT Class – XII


ALKYL HALIDE

            
          

    
    
    
   
   

   

        
       

     

         
    

   

    
    


          

        

              
         

         

         
      

        

              
 
       

            
           
   
 

        

           
          
           
          


FIITJEE



  
 
        
        

           

 

           

     
      
       
                

      

                

            

   
 
   


             

            

        

         
       
       
         
       
         
       
       
          
       

             
 

  
               
             
          
             

   

       
           
     
       
            
      


FIITJEE
