Q21Written answer
Chloromethane on treatment with an excess of ammonia yields mainly
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Worked solution
Option (iii) is the answer.
NCERT Exemplar · Class 12 · Chemistry
Chapter 10: Haloalkanes and Haloarenes
Practice each question, then open the answer or worked solution.
Questions
55 questionsQ22Multiple choice
Molecules whose mirror image is non-superimposable over them are known
as chiral. Which of the following molecules is chiral?
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Correct option: A
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Option (i) is the answer.
Q23Written answer
Reaction of C6H5CH2Br with aqueous sodium hydroxide follows ____________.
(i) SN1 mechanism
(ii) SN2 mechanism
(iii) Any of the above two depending upon the temperature of the reaction
(iv) Saytzeff rule
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Option (i) is the answer.
Q24Multiple choice
Which of the carbon atoms present in the molecule given below are asymmetric?
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Correct option: B
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Option (ii) is the answer.
Q25Multiple choice
Which of the following compounds will give racemic mixture on nucleophilic
substitution by OH– ion?
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Correct option: A
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Option (i) is the answer.
Note: In the questions, 26 to 29 arrange the compounds in increasing order
of the rate of reaction towards nucleophilic substitution.
26.
(i) (a) < (b) < (c)
(ii) (c) < (b) < (a)
(iii) (a) < (c) < (b)
(iv) (c) < (a) < (b)
Option (iii) is the answer.
27.
(i) (a) < (b) < (c)
(ii) (a) < (c) < (b)
(iii) (c) < (b) < (a)
(iv) (b) < (c) < (a)
Option (iv) is the answer.
28.
(i) (c) < (b) < (a)
(ii) (b) < (c) < (a)
(iii) (a) < (c) < (b)
(iv) (a) < (b) < (c)
Option (iv) is the answer.
29.
(i) (a) < (b) < (c)
(ii) (b) < (a) < (c)
(iii) (c) < (b) < (a)
(iv) (a) < (c) < (b)
Option (iii) is the answer.
Q26Multiple choice
(a)
(b)
(c)
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Correct option: C
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Ans: The Correct Answer is Option (iii).
Due to the resonance stabilisation of the benzene ring, the reactivity of aryl halides to nucleophilic substitution is exceedingly low. Because of resonance, the \[{\text{--Cl}}\] bond gains a partial double bond. The presence of an electron withdrawing \[{\text{--N}}{{\text{O}}_{\text{2}}}\] group at ortho or para positions on the ring enhances the reactivity of aryl halides. The presence of \[{\text{--N}}{{\text{O}}_{\text{2}}}\] near the \[{\text{C---Cl}}\] makes the molecule more reactive. The order of reactivity should be (b) > (c) > (a). The right option is (iii).
Q27Multiple choice
(a)
(b)
(c)
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Correct option: D
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Ans: The Correct Answer is Option (iv).
Because the \[{\text{--C}}{{\text{H}}_{\text{3}}}\] group is an electron releasing group, it reduces the reactivity of aryl halides in the ortho and para locations. As a result, aryl halides without electron releasing groups are more reactive. As a result, the order of reactivity is (a) > (c) > (d) (b). The right answer is (iv).
Q28Multiple choice
(a)
(b)
(c)
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Correct option: D
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Ans: The Correct Answer is option (iv).
(\[{\text{ - N}}{{\text{O}}_{\text{2}}}\]) is an electron-withdrawing group that induces nucleophilic substitution when it is in the ortho and para positions. When this identical electron-drawing group is in the meta position, its impact is much reduced. The reactivity of aryl halides rises as the number of electron-withdrawing groups increases. As a result, the greater the number of electron-drawing groups, the greater the rate of nucleophilic substitution.
Q29Multiple choice
(a)
(b)
(c)
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Correct option: C
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Ans: The Correct Answer is Option (iii).
The presence of electron releasing groups increases the reactivity of aryl halides; the fewer the electron releasing groups, the slower the rate of nucleophilic substitution. As a result, an increase in methyl groups decreases reactivity. The sequence of reactivity is (a) > (b) > (c). The right answer is (iii).
Q30Written answer
Which is the correct increasing order of boiling points of the following
compounds?
1-Iodobutane, 1-Bromobutane, 1-Chlorobutane, Butane
(i) Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane
(ii) 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane < Butane
(iii) Butane < 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane
(iv) Butane < 1-Chlorobutane < 1-Iodobutane < 1-BromobutaneSolution:
Option (i) is the answer.
31. Which is the correct increasing order of boiling points of the following compounds?
1-Bromoethane, 1-Bromopropane, 1-Bromobutane, Bromobenzene
(i) Bromobenzene < 1-Bromobutane < 1-Bromopropane < 1-Bromoethane
(ii) Bromobenzene < 1-Bromoethane < 1-Bromopropane < 1-Bromobutane
(iii) 1-Bromopropane < 1-Bromobutane < 1-Bromoethane < Bromobenzene
(iv) 1-Bromoethane < 1-Bromopropane < 1-Bromobutane < Bromobenzene
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Worked solution
Option (iv) is the answer
II. Multiple Choice Questions (Type-II)
Note: In the following questions two or more options may be correct.
Consider the following reaction and answer the questions no. 32–34.
