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Explore popular questions from Hydrocarbons for JEE Advanced. This collection covers Hydrocarbons previous year JEE Advanced questions hand picked by experienced teachers.

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Q 1. Marsh gas mainly contains

A

{tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 2 } {/tex}

{tex} \mathrm { CH } _ { 4 } {/tex}

C

{tex} \mathrm { H } _ { 2 } \mathrm { S } {/tex}

D

{tex} \mathrm { CO } {/tex}

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Q 2. The reaction conditions leading to the best yield of {tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 5 } \mathrm { Cl } {/tex} are

{tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 6 } ( \mathrm { excess } ) + \mathrm { Cl } _ { 2 } \stackrel { \mathrm { uvlight } } { \longrightarrow } {/tex}

B

{tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 6 } + \mathrm { Cl } _ { 2 }\xrightarrow[\mathrm{room temperature}]{\mathrm{dark}}{/tex}

C

{tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 6 } + \mathrm { Cl } _ { 2 } ( \text { excess } ) \stackrel { \text { uv light } } { \longrightarrow } {/tex}

D

{tex} \mathrm { C } _ { 2 } \mathrm { H } _ { 6 } + \mathrm { Cl } _ { 2 } \stackrel { \text { uv light } } { \longrightarrow } {/tex}

Explanation

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Q 3. Which of the following will have least hindered rotation about carbon-carbon bond?

Ethane

B

Ethylene

C

Acetylene

D

hexachloroethane

Explanation

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Q 4. When cyclohexane is poured on water, it floats, because:

A

cyclohexane is in 'boat' form

B

cyclohexane is in 'chair' form

C

cyclohexane is in 'crown' form

cyclohexane is less dense than water.

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Q 5. Consider the follwing reaction:
Identify the structure of the major product {tex}\mathrm{'X'}{/tex}

A

C

D

Explanation

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Q 6. In the given conformation,
{tex} \mathrm { C } _ { 2 } {/tex} is rotated about {tex} \mathrm { C } _ { 2 } - \mathrm { C } _ { 3 } {/tex} bond clockwise by an of angle {tex} 120 ^ { \circ } . {/tex} The obtained conformation is

A

anti conformation

gauche conformation

C

partially eclipsed conformation

D

fully eclipsed conformation

Explanation

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Q 7. Anti-Markovnikov addition of {tex}\mathrm{HBr}{/tex} is not observed in

A

propene

B

butene

{tex}2{/tex}-butene

D

{tex}2{/tex}-pentene

Explanation

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Q 8. Of the following compounds, which will have a zero dipole moment?

A

{tex} 1,1 {/tex}-dichlorothylene

B

cis-{tex}1,2{/tex}-dichloroethylene

trans-{tex}1,2{/tex}-dichloroethylene

D

none of these compounds

Explanation

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Q 9. {tex} n {/tex} - Propyl bromide on treating with ethanolic potassium hydroxide produces

A

propane

propene

C

propyne

D

propanol

Explanation

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Q 10. Which one of the following has the smallest heat of hydrogenation per mole?

A

{tex}1{/tex} -Butene

B

trans- {tex}2{/tex} - Butene

C

cis -{tex}2{/tex}-Butene

{tex} 1,3 {/tex} -Butadiene

Explanation

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Q 11. During debromoniation of meso-dibromobutane, the major compound formed is

A

{tex} n {/tex} -butane

B

{tex}1{/tex}-butene

C

cis- {tex}2{/tex} -butene

trans {tex} - 2 {/tex} -butene.

Explanation

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Q 12. The intermediate during the addition of {tex} \mathrm { HCl } {/tex} to propene in the presence of peroxide is

A

{tex} \mathrm { CH } _ { 3 } \mathrm { CHCH } _ { 2 } \mathrm { Cl } {/tex}

{tex} \mathrm { CH } _ { 3 } \mathrm {\stackrel{+} CHCH } _ { 3 } {/tex}

C

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

D

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm {\stackrel{+}CH } _ { 2 } {/tex}

Explanation

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Q 13. In the presence of peroxide, hydrogen chloride and hydrogen iodide do not give anti-Markovnikov addition to alkenes because

A

both are highly ionic

B

one is oxidising and the other is reducing

one of the steps is endothermic in both the cases

D

all the steps are exothermic in both the cases

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Q 14. When propyne is treated with aqueous {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } {/tex} in the presence of {tex} \mathrm { HgSO } _ { 4 } {/tex}, the major product is

A

propanol

B

propyl hydrogen sulphate

acetone

D

propanal

Explanation

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Q 15. Identify the set of reagents/reaction conditions {tex}\mathrm{'X'}{/tex} and {tex}\mathrm{'Y'}{/tex} in the following set of transformations:

A

{tex} \mathrm { X } = {/tex} dilute aqueous {tex} \mathrm { NaOH } , 20 ^ { \circ } \mathrm { C } ; \mathrm { Y } = \mathrm { HBr } / \mathrm { acetic } {/tex} acid {tex} , 20 ^ { \circ } \mathrm { C } {/tex}

{tex} \mathrm { X } = {/tex} concentrated alcoholic {tex} \mathrm { NaOH } , 80 ^ { \circ } \mathrm { C } ; \mathrm { Y } = \mathrm { HBr } / \mathrm { acetic } {/tex} acid {tex} , 20 ^ { \circ } \mathrm { C } {/tex}

C

{tex} \mathrm { X } = {/tex} dilute aqueous {tex} \mathrm { NaOH } , 20 ^ { \circ } \mathrm { C } ; \mathrm { Y } = \mathrm { HBr } / \mathrm { CHCl } _ { 3 } , 0 ^ { \circ } \mathrm { C } {/tex}

D

{tex} \mathrm { X } = {/tex} concentrated alcoholic {tex} \mathrm { NaOH } , 80 ^ { \circ } \mathrm { C } ; \mathrm { Y } = \mathrm { Br } _ { 2 } / \mathrm { CHCl } _ { 3 } , 0 ^ { \circ } \mathrm { C } {/tex}

Explanation

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Q 16. What is the decreasing order of strength of the bases {tex} \mathrm { OH } ^ { - } , \mathrm { NH } _ { 2 } ^ { - } , \mathrm { HC }\equiv \stackrel{-} { \mathrm { C } } {/tex} and {tex} \mathrm { CH } _ { 3 } \mathrm { CH^- }_{2} {/tex}

{tex} \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } ^ { - } > \mathrm { NH } _ { 2 } ^ { - } > \mathrm { H } - \mathrm { C } \equiv \mathrm { C } ^ { - } > \mathrm { OH } {/tex}

B

{tex} \mathrm { H } - \mathrm { C } = \mathrm { C } ^ { - } > \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } ^ { - } > \mathrm { NH } _ { 2 } ^ { - } > \mathrm { OH } ^ { - } {/tex}

C

{tex} \mathrm { OH } ^ { - } > \mathrm { NH } _ { 2 } ^ { - } > \mathrm { HC } \equiv \mathrm { C } ^ { - } > \mathrm { CH } _ { 3 } - \mathrm { CH^- } _ { 2 } {/tex}

D

{tex} \mathrm { NH } _ { 2 } ^ { - } > \mathrm { H } - \mathrm { C } \equiv \mathrm { C } ^ { - } > \mathrm { OH } ^ { - } > \mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } ^ { - } {/tex}

Explanation

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Q 17. The product(s) obtained via oxymercuration {tex} \left( \mathrm { HgSO } _ { 4 } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \right) {/tex} of {tex}1{/tex}-butyne would be

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

B

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

C

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CHO } + \mathrm { HCHO } {/tex}

D

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { COOH } + \mathrm { HCOOH } {/tex}

Explanation

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Q 18. In the reaction {tex} \mathrm { CH } _ { 3 } - \mathrm { CH } = \mathrm { CH } _ { 2 } \stackrel { \mathrm { NoCl } } { \longrightarrow } \mathrm { A } , {/tex} the compound {tex}\mathrm { A }{/tex} is

A

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } ( \mathrm { NO } ) \mathrm { CH } _ { 2 } \mathrm { Cl } {/tex}

{tex} \mathrm { CH } _ { 3 } \mathrm { CHClCH } _ { 2 } \mathrm { NO } {/tex}

C

{tex} \mathrm { CH } _ { 2 } ( \mathrm { NO } ) \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { Cl } {/tex}

D

{tex} \mathrm { CH } _ { 3 } \mathrm { CH } ( \mathrm { Cl } ) \mathrm { CH } _ { 2 } \mathrm { CH } ( \mathrm { Cl } ) \mathrm { CH } _ { 3 } {/tex}

Explanation

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Q 19. Propyne and propene can be distinguished by

A

conc. {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } {/tex}

B

{tex} \mathrm { Br } _ { 2 } {/tex} in {tex} \mathrm { CCl } _ { 4 } {/tex}

C

dil. {tex}\mathrm{KMnO}_{4}{/tex}

{tex}\mathrm{AgNO_3}{/tex} in ammonia

Explanation

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Q 20. Identify a reagent from the following list which can easily distinguish between 1-butene and 2 -butyne:

A

bromine,{tex}\mathrm{CCl}_{4}{/tex}

B

{tex} \mathrm { H } _ { 2 } , {/tex} Lindlar catalyst

C

dilute {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } , \mathrm { HgSO } _ { 4 } {/tex}

ammoniacal {tex} \mathrm { Cu } _ { 2 } \mathrm { Cl } _ { 2 } {/tex} solution

Explanation

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Q 21. Which of the following reagents is used for the conversion of {tex}2{/tex} -hexyne into cis-{tex}2{/tex}-hexene?

{tex} \mathrm { H } _ { 2 } / \mathrm { Pd } - \mathrm { BaSO } _ { 4 } {/tex}

B

{tex} \mathrm { H } _ { 2 } , \mathrm { Pt } {/tex}

C

{tex} \mathrm { Zn } / \mathrm { HCl } {/tex}

D

{tex} \mathrm { Li } - \mathrm { NH } _ { 3 } / \mathrm { C } _ { 2 } \mathrm { H } _ { 5 } \mathrm { OH } {/tex}

Explanation

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Q 22. Hyperconjugation involves overlap of the following orbitals

A

{tex} \sigma - \sigma {/tex}

{tex} \sigma - p {/tex}

C

{tex} p - p {/tex}

D

{tex} \pi - \pi {/tex}

Explanation

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Q 23. The correct stability order for the following species is

A

{tex} ( \mathrm { II } ) > ( \mathrm { IV } ) > ( \mathrm { I } ) > ( \mathrm { III } ) {/tex}

B

{tex} ( \mathrm { I } ) > ( \mathrm { II } ) > ( \mathrm { III } ) > ( \mathrm { IV } ) {/tex}

C

{tex} ( \mathrm { II } ) > ( \mathrm { I } ) > ( \mathrm { IV } ) > ( \mathrm { III } ) {/tex}

{tex} ( \mathrm { I } ) > ( \mathrm { III } ) > ( \mathrm { II } ) > ( \mathrm { IV } ) {/tex}

Explanation

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Q 24. The compounds {tex} \mathrm { P } , \mathrm { Q } {/tex} and {tex} \mathrm { S } {/tex}

were separately subjected to nitration using {tex} \mathrm { HNO } _ { 3 }/ \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } {/tex} mixture. The major product formed in each case respectively, is

A

B

D

Explanation

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Q 25. Among the following, the compound that can be most readily sulphonated is

A

benzene

B

nitrobenzene

toluene

D

chlorobenzene

Explanation