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JEE Main

Explore popular questions from Haloalkanes and Haloarenes for JEE Main. This collection covers Haloalkanes and Haloarenes previous year JEE Main questions hand picked by experienced teachers.

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Haloalkanes and Haloarenes

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Q 1.
{tex}Z{/tex} is

A

{tex} \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 3 } {/tex}

B

{tex} \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 3 } {/tex}

{tex} \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 3 } {/tex}

D

Explanation

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Q 2. An {tex} S _ { N }1 {/tex} reaction at the asymmetric carbon of an enantiomerically pure chiral alkyl halide gives an product:

A

with retention of configuration

B

with inversion of configuration

with racemisation

D

with partial racemisation

Explanation

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Q 3. Which of the following statements is incorrect for ethylene dichloride and ethylidene chloride?

A

These are structural isomers

B

Both of these yield same product on reaction with alcoholic KOH solution

Both of these yield same product on treatment with aqueous KOH solution

D

Both of these yield same product on reduction

Explanation

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Q 4.
The major product in this reaction is:

B

C

D

Explanation

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Q 5. The reaction is:

an {tex} \mathrm { S } _ { \mathrm { N } } 1 {/tex} reaction

B

an {tex} \mathrm { S } _ { \mathrm { N } } 2 {/tex} reaction

C

an {tex} \mathrm { S } _ { \mathrm { N } } \mathrm 3{/tex} reaction

D

None of these

Explanation

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Q 6. Which chloride is least reactive with the hydrolysis point of view ?

A

B

C

Explanation

The halogen atom in vinyl chloride is not reactive as in other alkyl halides. The non-reactivity of chlorine atom is due to resonance stabilisation. The 1.p. on Cl- atom can participate in delocalisation (Resonance) to give two canonical structure

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Q 7. In a SN2 substitution reaction of the type which one of the following has the highest relative rate

A

B

C

Explanation

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Q 8. Which of the following reactions will result in the formation of a chiral centre in the product?

A

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } = \mathrm { CH } _ { 2 } + \mathrm { HBr } \longrightarrow {/tex}

B

{tex} \mathrm { CH } _ { 2 } = \mathrm { CH } _ { 2 } + \mathrm { HOBr } \longrightarrow {/tex}

C

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CH } = \mathrm { CH } _ { 2 } + \mathrm { HBr } \longrightarrow {/tex}

Explanation

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Q 9. The reaction of {tex} ( S ) - 2 {/tex} -bromobutane with {tex} \mathrm { OH } ^ { - } {/tex} to produce (R)-butan-{tex}2{/tex}-ol will be

A

first order in {tex}2{/tex}-bromobutane only

B

first order in {tex} \mathrm { OH } ^ { - } {/tex} only

first order in {tex}2{/tex}-bromobutane and first order in {tex} \mathrm { OH } ^ { - } {/tex}

D

second order in {tex} \mathrm { OH } ^ { - } {/tex}

Explanation

Configuration invert, means SN2 reaction takes place Rate = K [Substrate][OH]

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Q 10. What is the major product of the following reaction?

B

C

D

None of these

Explanation

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Q 11. Consider the reactions:

The mechanisms of reactions (i) and (ii) are respectively:

SN1 and SN2

B

SN1 and SN1

C

SN2 and SN2

D

SN2 and SN1

Explanation

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Q 12. Aryl halide is less reactive than alkyl halide towards nucleophilic substitution because:

A

of less stable carbonium ion

due to large C-Cl bond energy

C

of inductive effect

D

of resonance stabilization and sp2 hybridization of C attached to halide

Explanation

Aryl halide is less reactive than alkyl halide towards nucleophilic substitution because of the resonance stabilization and sp2 hybridization of C attached to halide. Due to resonance, carbon-chlorine bond acquires partial double bond character, hence it becomes shorter and stronger, and thus, cannot be easily replaced by nucleophiles. This effect is further enhanced by the sp2 nature of the C atom to which chlorine is attached.

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Q 13. Identify {tex} ( \mathrm { X } ): {/tex}

{tex} \mathrm { F } _ { 2 } \mathrm { C } = \mathrm { CF } _ { 2 } {/tex}

B

{tex} \mathrm { ClFC } = \mathrm { CFCl } {/tex}

C

{tex} \mathrm { F } _ { 2 } \mathrm { C } = \mathrm { CFCl } {/tex}

D

{tex} \mathrm { F } _ { 2 } \mathrm { C } = \mathrm { CCl } _ { 2 } {/tex}

Explanation

2CHF2Cl ---> F2C=CF2 + 2HCl

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Q 14. Chloropicrin is a strong lachrymatory compound and is used in war. It is prepared by:

A

heating acetone with chloroform in the presence of dilute NaOH.

heating chloroform with {tex} \mathrm { HNO } _ { 3 } {/tex}

C

heating nitormethane with carbon tetrachloride.

D

the reaction of acetylene and arsenic chloride.

Explanation

Because of the precursor used, Stenhouse named the compound chloropicrin, although the two compounds are structurally dissimilar. Today, chloropicrin is manufactured by the reaction of nitromethane with sodium hypochlorite H3CNO2 + 3 NaOCl → Cl3CNO2 + 3 NaOH or by the reaction of chloroform with nitric acid CHCl3 + HNO3 → CCl3NO2 + H2O

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Q 15. Arrange the following compounds in the increasing order of their boiling points:

A

{tex} ( b ) < ( a ) < ( c ) {/tex}

B

(a) {tex} < ( b ) < ( c ) {/tex}

{tex} ( c ) < ( a ) < ( b ) {/tex}

D

{tex} ( c ) < ( b ) < ( a ) {/tex}

Explanation

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Q 16. Isopropylidene chloride is hydrolysed with aqueous NaOH. The product formed is:

A

1-propanal

B

propanal

C

2-propanal

propanone

Explanation

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Q 17. Fluorobenzene {tex} \left( \mathrm { C } _ { 6 } \mathrm { H } _ { 5 } \mathrm { F } \right) {/tex} can be synthesized in the laboratory

A

by direct fluorination of benzene with {tex} \mathrm { F } _ { 2 } {/tex} gas

B

by reacting bromobenzene with NaF solution

C

by heating phenol with HF and KF

from aniline by diazotisation followed by heating the diazonium salt with {tex} \mathrm { HBF } _ { 4 } {/tex}

Explanation

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Q 18. Consider the following bromides:

The correct order of {tex} S_{N} 1 {/tex} reactivity is

{tex} B > C > A {/tex}

B

{tex} B > A > C {/tex}

C

{tex} \mathrm { C } > \mathrm { B } > \mathrm { A } {/tex}

D

{tex} A > B > C {/tex}

Explanation







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Q 19. The organic chloro compound, which shows complete sterochemical inversion during a {tex} \mathrm { S } _ { \mathrm { N } } 2 {/tex} reaction, is

A

{tex} \left( \mathrm { C } _ { 2 } \mathrm { H } _ { 5 } \right) _ { 2 } \mathrm { CHCl } {/tex}

B

{tex} \left( \mathrm { CH } _ { 3 } \right) _ { 3 } \mathrm { CCl } {/tex}

C

{tex} \left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm { CHCl } {/tex}

{tex} \mathrm { CH } _ { 3 } \mathrm { Cl } {/tex}

Explanation



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Q 20. Phenyl magnesium bromide reacts with methanol to give

A

a mixture of toluene and Mg (OH) Br

B

a mixture of phenol and Mg(Me) Br

C

a mixture of anisole and Mg(OH)Br

a mixture of benzene and Mg(OMe) Br

Explanation

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Q 21. Tertiary alkyl halides are practically inert to substitution by {tex} \mathrm { S } _ { \mathrm { N } } 2 {/tex} mechanism because of

A

steric hindrance

inductive effect

C

instability

D

insolubility

Explanation



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Q 22. Alkyl halides react with dialkyl copper reagents to give

A

alkenyl halides

alkanes

C

alkyl copper halides

D

alkenes

Explanation



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Q 23. Elimination of bromine from 2 -bromobutane results in the formation of {tex} - {/tex}

A

Predominantly 2 -butyne

B

Predominantly 1 -butene

Predominantly 2 -butene

D

equimolar mixture of 1 and 2 -butene

Explanation

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Q 24. Compound (A), {tex} \mathrm { C } _ { 8 } \mathrm { H } _ { 9 } \mathrm { Br } {/tex} , gives a white precipitate when warmed with alcoholic {tex} \mathrm { AgNO } _ { 3 } {/tex} . Oxidation of (A) gives an {tex} \operatorname { acid } ( \mathrm { B } ) , \mathrm { C } _ { 8 } \mathrm { H } _ { 6 } \mathrm { O } _ { 4 } {/tex} . (B) easily forms anhydride on heating. Identify the compound (A).

A

B

C

Explanation

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Q 25. The major organic compound formed by the reaction of {tex} 1,1,1 {/tex} -trichloroethane with silver powder is:

A

Acetylene

B

Ethene

2 - Butyne

D

{tex} 2 - {/tex} Butene

Explanation