Haloalkanes and Haloarenes Class 12 MCQs Questions with Answers

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Question 1.
The most reactive nucleophile among the following is
(a) CH3O–
(b) C6H5O–
(c) (CH3)2CHO–
(d) (CH3)3 CO–

Answer

Answer: (a) CH3O–

Question 2.
CH3CH2CHCl CH3 obtained by chlorination of n-butane, will be
(a) meso-form
(b) racemic mixture
(c) d-form
(d) 1-form

Answer

Answer: (b) racemic mixture

Question 3.
In Friedel-Crafts synthesis of toluene, reactants in addition to anhydrous AlCl3 are:
(a) C6H6 + CH4
(b) C6H6 + CH3Cl
(c) C5H5Cl + CH3Cl
(d) C6H5/sub>Cl + CH4

Answer

Answer: (b) C6H6 + CH3Cl

Question 4.
SN1 reaction of alkyl halides leads to
(a) retention of configuration
(b) racemisation
(c) inversion of configuration
(d) none of these.

Answer

Answer: (b) racemisation

Question 5.
Nucleophilieity order is correctly represented by


Answer

Answer: (c)

Question 6.
Which of the following are arranged in the decreasing order of dipole moment?
(a) CH3Cl, CH3Br, CH2F
(b) CH3Cl, CH3F, CH3Br
(c) CH3Br, CH3Cl, CH3F
(d) CH3Br, CH3F, CH3Cl

Answer

Answer: (b) CH3Cl, CH3F, CH3Br

Question 7.
Which of the following is a free radical substitution reaction?













(d) CH3CHO + HCN → CH3CH (OH) CN

Answer

Answer: (a)

Question 8.
The reactivity order of halides for dehydrogenation is
(a) RF > RCl > RBr > RI
(b) RI > RBr > RCl > RF
(c) RI > RCl > RBr > RF
(d) RF > RI > RBr > RCl

Answer

Answer: (b) RI > RBr > RCl > RF

Question 9.
The addition of HBr is easiest with
(a) CH2 = CHCl
(b) ClCH = CHCl
(c) CH3-CH = CH2
(d) (CH3)2C = CH2

Answer

Answer: (d) (CH3)2C = CH2

Question 10.
Among the following compounds, the decreasing order of reactivity towards electrophilic substitution is







(a) III > I > II > IV
(b) IV > I > II > III
(c) I > II > III > IV
(d) II > I > III > IV

Answer

Answer: (a) III > I > II > IV

Question 11.
Unpleasant smelling carbylamines are formed by heating alkali and chloroform with
(a) Any aliphatic amine
(b) Any aromatic amine
(c) Any amine
(d) Any primary amine

Answer

Answer: (d) Any primary amine

Question 12.
Which among MeX, R-CH2X, R2CHX, R3CX is most reactive towards SN2 reaction
(a) MeX
(b) RCH2X
(c) R3CHX
(d) R3CX

Answer

Answer: (a) MeX

Question 13.
Number of stereoisomers of the compound 2-chloro-4- methylhex-2-ene is /are
(a) 1
(b) 2
(c) 4
(d) 16

Answer

Answer: (c) 4

Question 14.
In chlorination of benzene, the reactive species is
(a) Cl+
(b) Cl–
(c) Cl2
(d) Cl−2

Answer

Answer: (a) Cl+

Question 15.
An organic compound, on treatment with Br2 in CCl4 gives bromo derivative of an alkene. The compound will be
(a) CH4-CH = CH2
(b) CH3-CH = CH-CH3
(c) HC = CH
(d) H2C = CH2

Answer

Answer: (c) HC = CH

Question 16.
If one H is replaced by a Cl atom in C4H9Cl, the total number of structural isomers will be
(a) 4
(b) 5
(c) 7
(d) 10

Answer

Answer: (d) 10

Question 17.
Anti-Markovnikov addition of HBr is not observed in
(a) Propene
(b) 1-Butene
(c) But-2-ene
(d) Pent-2-ene

Answer

Answer: (c) But-2-ene

Question 18.
Among the following, the molecule with the highest dipole moment is
(a) CH3Cl
(b) CH2Cl2
(c) CHCl3
(d) CCl4

Answer

Answer: (a) CH3Cl

Question 19.
The number of isomers for the compound with molecular formula C2 Br Cl FI is
(a) 3
(b) 4
(c) 5
(d) 6

Answer

Answer: (d) 6

Question 20.
(CH3)3 C MgBr on reaction with D2O produces
(a) (CH3)3CD
(b) (CH3)3COD
(c) (CH3)3CD
(d) (CD3)3OD

Answer

Answer: (a) (CH3)3CD

Question 21.
A solution (+) -2-chloro-2-phenylethane in toluene racemises slowly in the presence of small amount of SbCl5, due to the formation of
(a) Carbanion
(b) Carbene
(c) Free radical
(d) Carbocation

Answer

Answer: (d) Carbocation

Question 22.
In the addition of HBr to propene in the absence of peroxides, the fist step involves the addition of
(a) H+
(b) Br–
(c) H°
(d) Br°

Answer

Answer: (a) H+

Question 23.
In the reaction of p-Chlorotoluene with KNH2 in liq. NHy the major product is
(a) o-toluidine
(b) m-toluidine
(c) p-toluidine
(d) p-chloro aniline

Answer

Answer: (b) m-toluidine

Question 24.
During debromination of meso-dibromo butane, the major compound formed is
(a) n-butane
(b) 1-butene
(c) cis-2-butene
(d) trans-2-butene.

Answer

Answer: (d) trans-2-butene.

Question 25.
The number of possible enantiomeric pairs that can be produced during monochlorination of 2-methyl butane is
(a) 2
(b) 3
(c) 4
(d) 1

Answer

Answer: (a) 2

Question 26.
Arrange the following compounds in order of increasing dipole moment: Toluene (I), m-dichlorobenzene (II), o- dichlorobenzene (III) and p-dichlorobenzene (IV).
(a) I < IV < II < III
(b) IV < r < II < III
(c) IV < I < III < II
(d) IV < II < I < III

Answer

Answer: (b) IV < r < II < III

Question 27.
In the following groups : – O Ac (I), – O Me (II), – O SO2 Me (III), – OSO2 CF3 (IV), The order of leaving group ability is
(a) I > II > III > IV
(b) IV > III > I > II
(c) m > II > I > IV
(d) II > III > IV > I

Answer

Answer: (b) IV > III > I > II

Question 28.
Identify the set of reagent/reaction conditions X and Y in the following set of transformations:







(a) X = dil. aqueous NaOH, 20° C, Y = HBr/Acetic acid, 20°C
(b) X = Cone, alcoholic NaOH, 80°C, Y = HBr/acetic acid, 20°C
(c) X = dil. aqueous NaOH, 20°C Y – Br2/CHCl3,0°C
(d) X = Cone, alcoholic NaOH, 80°C, Y = Br2/CHCl3, 0°C.

Answer

Answer: (b) X = Cone, alcoholic NaOH, 80°C, Y = HBr/acetic acid, 20°C

Question 29.
In the presence of peroxide, hydrogen chloride and hydrogen iodide do not give anti-Markovnikov’s addition to alkenes because
(a) both are highly ionic
(b) one is oxidizing and the other is reducing
(c) one of the steps is endothermic in both the cases
(d) all the steps are exothermic in both the reactions

Answer

Answer: (c) one of the steps is endothermic in both the cases

Question 30.
When chlorine is passed through propene at 400°C, which of the following is formed?
(a) FVC
(b) Allyl Chloride
(c) Vinyl Chloride
(d) 1,2-Dichloroethane

Answer

Answer: (b) Allyl Chloride

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