jee main chemistry important questions | Hydrocarbons jee main questions FREE

Q 1 :

Number of compounds from the following which cannot undergo Friedel-Crafts reaction is ______.
toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene. [2024]

(4)

$C_{6} H_{5} - G \to no Friedel Craft acylation or alkylation.$

$G = (i) all -M groups such as - CHO, - {NO}_{2}, - COCl, - CN etc$

$(ii) Very strong +M groups such as - {CH}_{2}^{-}, - {NH}^{-}, - O^{-}, - OH, - {NH}_{2}, - NHR, and - {NR}_{2}$

${(iii) Very strong -I groups such as -CX}_{3}, - {NH}_{3}^{+} and {}^{+}{NH}_{3}$

$Thus, nitrobenzene, aniline, m-nitroaniline and m-dinitrobenzene cannot undergo Friedel Crafts reaction.$

Q 2 :

Which of the following molecule/species is most stable? [2024]

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(1)

Cyclic, planar compounds having completely delocalized $(4 n + 2) π$ electrons ( $n$ = 1,2,3...)are aromatic. Aromatic compounds are highly stable. Cyclic, planar compounds having completely delocalized $4 nπ$ electrons ( $n$ = 1,2,3...) are anti-aromatic. Anti-aromatic compounds are highly unstable.

Q 3 :

Identify major product ‘P’ formed in the following reaction. [2024]

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(2)

Q 4 :

The correct order of reactivity in electrophilic substitution reaction of the following compounds is: [2024]

D > C > B > A
B > C > A > D
A > B > C > D
B > A > C > D

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(4)

Reactivity of the benzene ring towards an electrophile is directly proportional to electron density on the ring.

$- {CH}_{3}$ supplies electrons to benzene by its hyperconjugation and $+ I$ effect.

$- Cl$ Has +M effect and $- I$ effect. The $- I$ effect of $- Cl$ is more than its +M effect. Hence, $- Cl$ decreases electron density on benzene and reduces its reactivity towards electrophilic substitution reactions.

$- {NO}_{2}$ Has –M and $- I$ effect.

Q 5 :

Which of the following compound will most easily be attacked by an electrophile? [2024]

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(4)

Reactivity of benzene ring towards an electrophile is directly proportional to electron density on the ring.
–OH exerts more electron density on the ring than the given groups $- {CH}_{3}$ and $Cl$ and therefore make more appropriate to electrophilic attack.

Q 6 :

Given below are two statements:

Statement I: Nitration of benzene involves the following step –

Statement II: Use of Lewis base promotes the electrophilic substitution of benzene.

In the light of the above statements, choose the most appropriate answer from the options given below: [2024]

Statement I is correct but Statement II is incorrect
Both Statement I and Statement II are correct
Statement I is incorrect but Statement II is correct
Both Statement I and Statement II are incorrect

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(1)

In nitration of benzene, commonly used reagent is conc. ( $H_{2} {SO}_{4} + {HNO}_{3}$ ). This generates electrophile as follows:

In electrophilic substitution of benzene, Lewis acid helps in generation of electrophile, not Lewis base.

Q 7 :

Identify major product ‘X’ formed in the following reaction: [2024]

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(2)

This is Gatterman Koch reaction.

Q 8 :

Which of the following are aromatic? [2024]

C and D only
B and D only
A and C only
A and B only

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(2)

B and D are aromatic.

Q 9 :

Among the given organic compounds, the total number of aromatic compounds is : [2024]

(3)

Q 10 :

The product (C) in the following sequence of reactions has ______ $π$ bonds. [2024]

(4)

Number of $π$ bonds in C = 4

Q 11 :

Total number of aromatic compounds among the following compounds is _____. [2024]

(1)

Q 12 :

[2023]

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(1)

Q 13 :

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Benzene is more stable than hypothetical cyclohexatriene.

Reason R: The delocalized $π$ electron cloud is attracted more strongly by nuclei of carbon atoms.

In the light of the above statements, choose the correct answer from the options given below: [2023]

A is false but R is true
Both A and R are correct but R is NOT the correct explanation of A
A is true but R is false
Both A and R are correct and R is the correct explanation of A

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(4)

Benzene has resonance energy 36 Kcal per mole.

Q 14 :

Among the following compounds, the one which shows highest dipole moment is [2023]

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(1)

The given compound has the highest dipole moment because both rings become aromatic, that is why most polar compound.

Q 15 :

Given below are two statements:

Statement I: Tropolone is an aromatic compound and has 8 $π$ electrons.

Statement II: $π$ electrons of $> C = O$ group in tropolone is involved in aromaticity.

In the light of the above statements, choose the correct answer from the options given below: [2023]

Statement I is true but Statement II is false
Both Statement I and Statement II are false
Statement I is false but Statement II is true
Both Statement I and Statement II are true

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(1)

Q 16 :

Identify the correct statements:

The presence of $- {NO}_{2}$ group in benzene ring

A. activates the ring towards electrophilic substitutions.
B. deactivates the ring towards electrophilic substitutions.
C. activates the ring towards nucleophilic substitutions.
D. deactivates the ring towards nucleophilic substitutions.

Choose the correct answer from the options given below: [2026]

A and D Only
B and D Only
C and A Only
B and C Only

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(4)

Presence of ${NO}_{2}$ group in benzene ring deactivates the ring towards electrophilic substitution reaction due to −M effect and activates the ring towards nucleophilic substitution.

Ans. → (4) B & C

Topic Question Set

Q 1 :

Number of compounds from the following which cannot undergo Friedel-Crafts reaction is ______.
toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene. [2024]

Q 2 :

Which of the following molecule/species is most stable? [2024]

Q 3 :

Identify major product ‘P’ formed in the following reaction. [2024]

Q 4 :

The correct order of reactivity in electrophilic substitution reaction of the following compounds is: [2024]

Q 5 :

Which of the following compound will most easily be attacked by an electrophile? [2024]

Q 7 :

Identify major product ‘X’ formed in the following reaction: [2024]

Q 8 :

Which of the following are aromatic? [2024]

Q 9 :

Among the given organic compounds, the total number of aromatic compounds is : [2024]

Q 10 :

The product (C) in the following sequence of reactions has ______ $π$ bonds. [2024]

Q 11 :

Total number of aromatic compounds among the following compounds is _____. [2024]

Q 12 :

[2023]

Q 14 :

Among the following compounds, the one which shows highest dipole moment is [2023]

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Topic Question Set

Q 1 : Number of compounds from the following which cannot undergo Friedel-Crafts reaction is ______. toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene. [2024]

Q 2 : Which of the following molecule/species is most stable? [2024]

Q 3 : Identify major product ‘P’ formed in the following reaction. [2024]

Q 4 : The correct order of reactivity in electrophilic substitution reaction of the following compounds is: [2024]

Q 5 : Which of the following compound will most easily be attacked by an electrophile? [2024]

Q 6 : Given below are two statements: Statement I: Nitration of benzene involves the following step – Statement II: Use of Lewis base promotes the electrophilic substitution of benzene. In the light of the above statements, choose the most appropriate answer from the options given below: [2024]

Q 7 : Identify major product ‘X’ formed in the following reaction: [2024]

Q 8 : Which of the following are aromatic? [2024]

Q 9 : Among the given organic compounds, the total number of aromatic compounds is : [2024]

Q 10 : The product (C) in the following sequence of reactions has ______ π bonds. [2024]

Q 11 : Total number of aromatic compounds among the following compounds is _____. [2024]

Q 12 : [2023]

Q 14 : Among the following compounds, the one which shows highest dipole moment is [2023]

Q 15 : Given below are two statements: Statement I: Tropolone is an aromatic compound and has 8 π electrons. Statement II: π electrons of >C=O group in tropolone is involved in aromaticity. In the light of the above statements, choose the correct answer from the options given below: [2023]

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Q 1 :

Number of compounds from the following which cannot undergo Friedel-Crafts reaction is ______.
toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene. [2024]

Q 2 :

Which of the following molecule/species is most stable? [2024]

Q 3 :

Identify major product ‘P’ formed in the following reaction. [2024]

Q 4 :

The correct order of reactivity in electrophilic substitution reaction of the following compounds is: [2024]

Q 5 :

Which of the following compound will most easily be attacked by an electrophile? [2024]

Q 7 :

Identify major product ‘X’ formed in the following reaction: [2024]

Q 8 :

Which of the following are aromatic? [2024]

Q 9 :

Among the given organic compounds, the total number of aromatic compounds is : [2024]

Q 10 :

The product (C) in the following sequence of reactions has ______ $π$ bonds. [2024]

Q 11 :

Total number of aromatic compounds among the following compounds is _____. [2024]

Q 12 :

[2023]

Q 14 :

Among the following compounds, the one which shows highest dipole moment is [2023]