jee main chemistry important questions | Organic Compounds Containing Halogens jee main questions FREE

Q 1 :

The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is: [2024]

Racemisation occurs in $S_{N} 1$ reaction and inversion occurs in $S_{N} 2$ reaction.
Racemisation occurs in $S_{N} 1$ reaction and retention occurs in $S_{N} 2$ reaction.
Retention occurs in $S_{N} 1$ reaction and inversion occurs in $S_{N} 2$ reaction.
Racemisation occurs in both $S_{N} 1$ and $S_{N} 2$ reactions.

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(1)

In $S_{N} 1$ reaction, carbocation is formed as an intermediate. Carbocation is planar and nucleophile may attack from either side of the plane. This gives a pair of enantiomers as reaction products i.e. product is racemic mixture. Although amount of inversion product is more than that of retention product because nucleophile starts attacking from back side even before leaving group has completely left the carbon. So in $S_{N} 1$ there is partial racemization.

In $S_{N} 2$ , there is 100% inversion because nucleophile attacks from the side opposite to leaving group.

Q 2 :

Given below are two statements:

Statement-I: High concentration of strong nucleophilic reagent with secondary alkyl halides which do not have bulky substituents will follow ${S_{N}}^{2}$ mechanism.

Statement-II: A secondary alkyl halide when treated with a large excess of ethanol follows ${S_{N}}^{1}$ mechanism.

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

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

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(4)

Secondary alkyl halide follows both $S_{N} 1$ and $S_{N} 2$ paths parallelly. Out of $S_{N} 1$ and $S_{N} 2$ , which one is preferred path by secondary alkyl halide depends upon other conditions such as strength of nucleophile and nature of solvent. Strong nucleophiles such as alkoxides and polar aprotic solvents such as DMF and DMSO prefer to keep the reaction along $S_{N} 2$ pathway. Weak nucleophiles such as water, alcohols and acetic acid and polar protic solvents such as water and alcohols (these are solvents as well as nucleophiles), prefer to keep the reaction along $S_{N} 1$ pathway.

Q 3 :

Given below are two statements:

Statement (I): $S_{N} 2$ reactions are 'stereospecific', indicating that they result in the formation of only one stereo-isomer as the product.

Statement (II): $S_{N} 1$ reactions generally result in formation of product as racemic mixtures.

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

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

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(1)

Stereospecific reactions are those reactions for which if stereochemistry of reactants is changed, then major product formed is changed. In $S_{N} 2$ reactions, inversion occurs, so different stereoisomers give different products. Hence $S_{N} 2$ reactions are stereospecific.

In $S_{N} 1$ reactions, carbocation is formed as intermediate. Carbocation is planar hence nucleophile can attack from either side of the planar carbocation. This results in racemic mixture in products.

Q 4 :

Which among the following halide/s will not show $S_{N} 1$ reaction: [2024]

Choose the most appropriate answer from the options given below:

(A), (B) and (D) only
(A) and (B) only
(B) and (C) only
(B) only

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(4)

Vinyl carbocation is unstable as it has positive charge on sp hybridized carbon. Hence, its formation is difficult and vinyl halides do not show $S_{N} 1$ reaction.

Vinyl, aryl and halides with halogen at the bridgehead position neither show $S_{N} 1$ nor $S_{N} 2$ reactions.

Q 5 :

Alkyl halide is converted into alkyl isocyanide by reaction with: [2024]

NaCN
AgCN
${NH}_{4} CN$
KCN

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(2)

Q 6 :

The product (C) in the below-mentioned reaction is: [2024]

Propene
Propan-2-ol
Propyne
Propan-1-ol

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(2)

Q 7 :

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). [2024]
Assertion (A): Haloalkanes react with KCN to form alkyl cyanides as a main product while with AgCN form isocyanide as the main product.

Reason (R): KCN and AgCN both are highly ionic compounds.

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

(A) is correct but (R) is not correct
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(A) is not correct but (R) is correct
Both (A) and (R) are correct and (R) is the correct explanation of (A)

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(1)

KCN is an ionic compound and predominantly exists as $K^{+}$ and $C N^{-}$ . In $C N^{-}$ both C and N have lone pairs ${}^{(-)}{(\overset{∙ ∙}{C} \equiv N)}$ and can participate in nucleophilic substitution reactions with haloalkanes. But C donates its lone pair in preference to N and cyanide is formed as chief product.

AgCN is a covalent compound; hence, carbon does not have a free lone pair to react ${(Ag - C \equiv N)}^{∙ ∙}$ . As only nitrogen has a lone pair, it reacts with haloalkanes to form isocyanides.

Q 8 :

Identify the correct set of reagents or reaction conditions 'X' and 'Y' in the following set of transformation. [2024]

X = dil. aq. NaOH, 20°C, Y = ${Br}_{2} / {CHCl}_{3}$
X = conc. alc. NaOH, 80°C, Y = HBr/acetic acid
X = dil. aq. NaOH, 20°C, Y = HBr/acetic acid
X = conc. alc. NaOH, 80°C, Y = ${Br}_{2} / {CHCl}_{3}$

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(2)

aq. NaOH causes substitution and alc. NaOH causes elimination.

Q 9 :

Product P is [2024]

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(2)

Q 10 :

Identify the major product in the following reaction. [2024]

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(4)

Q 11 :

Consider the above chemical reaction product ''A'' is: [2024]

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(1)

Because of $β$ crowding in the molecule, $S_{N} 1$ product is the major product.

Q 12 :

Which among the following compounds will undergo fastest $S_{N} 2$ reaction? [2024]

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(2)

Least crowded alkyl halide undergoes $S_{N} 2$ fastest, as nucleophile can approach the less crowded position with more ease. So order of reactivity of different alkyl halides for $S_{N} 2$ reaction is: $1 ° > 2 ° > 3 °$

Q 13 :

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

Assertion (A): $S_{N} 2$ reaction of $C_{6} H_{5} {CH}_{2} Br$ occurs more readily than the $S_{N} 2$ reaction of ${CH}_{3} {CH}_{2} Br$ .

Reason (R): The partially bonded unhybridized p-orbital that develops in the trigonal bipyramidal transition state is stabilized by conjugation with the phenyl ring.

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

Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(A) is correct but (R) is not correct.
(A) is not correct but (R) is correct.
Both (A) and (R) are correct and (R) is the correct explanation of (A).

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(4)

Q 14 :

In the following sequence of reaction, the major products B and C respectively are: [2024]

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(3)

Q 15 :

In the above reaction product 'P' is [2024]

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(3)

Aromatic ring present at $β$ position acts as neighbouring group.

Q 16 :

The total number of hydrogen atoms in product A and product B is _____. [2024]

(10)

Hydrogen atoms in A = 4, hydrogen atoms in B = 6, Sum = 10

Q 17 :

Given below are two statements: [2025]

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

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

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(2)

Statement I: Primary halides are almost unreactive towards $S_{N} 1$ reactions because primary carbocations are unstable. But carbocation of given halide is stabilized by +M effect of O, hence the given halide undergoes $S_{N} 1$ reaction.

Statement II: Primary halides with three alkyl groups at $β$ -position do not show $S_{N} 2$ reaction.

Q 18 :

Given below are two statements: [2025]

In the light of the above statements, choose the correct answer from the options given below.

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

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(3)

(I) More polar medium takes the system towards high charge density, hence this system will be reluctant to go to transition state in more polar medium. This reaction is thus more favourable in less polar medium.

Q 19 :

The structure of the major product formed in the following reaction is: [2025]

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(2)

Aryl halides are resistant to nucleophilic substitution reactions, so nucleophilic substitution occurs at aliphatic positions under normal conditions.

Q 20 :

The ascending order of relative rate of solvolysis of following compounds is: [2025]

(D) < (B) < (A) < (C)
(D) < (A) < (B) < (C)
(C) < (D) < (B) < (A)
(C) < (B) < (A) < (D)

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(2)

Q 21 :

The products A and B in the following reactions, respectively, are: [2025]

$A \overset{Ag - {NO}_{2}}{\to} {CH}_{3} - {CH}_{2} - {CH}_{2} - Br \overset{AgCN}{\to} B$

${CH}_{3} {CH}_{2} {CH}_{2} {NO}_{2}, {CH}_{3} {CH}_{2} {CH}_{2} CN$
${CH}_{3} {CH}_{2} {CH}_{2} ONO, {CH}_{3} {CH}_{2} {CH}_{2} NC$
${CH}_{3} {CH}_{2} {CH}_{2} ONO, {CH}_{3} {CH}_{2} {CH}_{2} CN$
${CH}_{3} {CH}_{2} {CH}_{2} {NO}_{2}, {CH}_{3} {CH}_{2} {CH}_{2} NC$

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(4)

Q 22 :

The product B formed in the following reaction sequence is: [2025]

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(4)

Q 23 :

The major product of the following reaction is: [2025]

2-Phenylhepta-2,4-diene
6-Phenylhepta-2,4-diene
2-Phenylhepta-2,5-diene
6-Phenylhepta-3,5-diene

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(1)

Q 24 :

In the following substitution reaction: [2025]

Product ‘P’ formed is:

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(4)

Electron withdrawing groups assist in nucleophilic substitution reactions for aromatic compounds. Because –M effect of – ${NO}_{2}$ is operative at para position, ${Br}^{-}$ from para position gets substituted.

Q 25 :

Given below are two statements: [2025]

Statement (I): Alcohols are formed when alkyl chlorides are treated with aqueous potassium hydroxide by elimination reaction.

Statement (II): In alcoholic potassium hydroxide, alkyl chlorides form alkenes by abstracting the hydrogen from the $β$ -carbon.

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

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

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(2)

Q 26 :

For the reaction

${RCH}_{2} Br + I^{-} \overset{Acetone}{\to} \underset{Major}{{RCH}_{2} I} + {Br}^{-}$

The correct statement is [2023]

The transition state formed in the above reaction is less polar than the localised anion.
The reaction can occur in acetic acid also.
${Br}^{-}$ can act as competing nucleophile.
The solvent used in the reaction solvates the ions formed in the rate-determining step.

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(1)

The given reaction is a $S_{N} 2$ reaction proceed via transition state mechanism which requires strong nucleophile in non polar or polar aprotic solvent. This medium provides transition state a less polar environment than that of localised anion.

Q 27 :

Choose the halogen which is most reactive towards $S_{N} 1$ reaction in the given compounds (A, B, C and D) [2023]

$A - {Br}_{(a)}; B - I_{(a)}; C - {Br}_{(b)}; D - {Br}_{(a)}$
$A - {Br}_{(b)}; B - I_{(a)}; C - {Br}_{(a)}; D - {Br}_{(a)}$
$A - {Br}_{(b)}; B - I_{(b)}; C - {Br}_{(b)}; D - {Br}_{(b)}$
$A - {Br}_{(a)}; B - I_{(a)}; C - {Br}_{(a)}; D - {Br}_{(a)}$

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(1)

The reactivity of halogen for $S_{N} 1$ reaction depends upon stability of carbocation:

A – ${Br}_{(a)} \Rightarrow$ Phenyl carbocation

B – $I_{(a)} \Rightarrow$ Allyl carbocation

C – ${Br}_{(b)} \Rightarrow$ 3° – carbocation

D – ${Br}_{(a)} \Rightarrow$ 3° – carbocation

Q 28 :

Identify the correct order of reactivity for the following pairs towards the respective mechanism. [2023]

Choose the correct answer from the options given below:

(A), (B) and (D) only
(A), (B), (C) and (D)
(B), (C) and (D) only
(A), (C) and (D) only

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(2)

Reactivity of $S_{N} 2 \propto \frac{1}{Steric crowding} (1 ° > 2 ° > 3 °) halide$

Reactivity of $S_{N} 1 \propto$ Stability of carbocation $(Benzyl cation > 1 ° -cation)$

Reactivity of electrophilic substitution reaction $\propto$ Electron density. ( $- Cl$ is more electron donating group, while $- {NO}_{2}$ is electron withdrawing group)

Reactivity of nucleophilic substitution reaction $\propto \frac{1}{Electron density}$

$- I$ effect group creates more reactive site for nucleophile.

$- I$ effect of ${NO}_{2} > - I$ effect of Br

Q 29 :

Compound from the following that will not produce precipitate on reaction with ${AgNO}_{3}$ is: [2023]

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(3)

Vinylic halides are inert towards ${AgNO}_{3}$ due to strong $C — X$ bond and less stable carbocation.

Q 30 :

2-Methyl propyl bromide reacts with $C_{2} H_{5} O^{-}$ and gives 'A' whereas on reaction with $C_{2} H_{5} OH$ it gives 'B'. The mechanism followed in these reactions and the products 'A' and 'B' respectively are: [2023]

$S_{N} 2, A = 2 - butyl ethyl ether; S_{N} 2, B=iso-butyl ethyl ether$
$S_{N} 2, A = iso - butyl ethyl ether; S_{N} 1, B = tert - butyl ethyl ether$
$S_{N} 1, A = tert - butyl ethyl ether; S_{N} 2, B = iso - butyl ethyl ether$
$S_{N} 1, A = tert - butyl ethyl ether; S_{N} 1, B = 2 - butyl ethyl ether$

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(2)

Topic Question Set

Q 1 :

The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is: [2024]

Q 4 :

Which among the following halide/s will not show $S_{N} 1$ reaction: [2024]

Choose the most appropriate answer from the options given below:

Q 5 :

Alkyl halide is converted into alkyl isocyanide by reaction with: [2024]

Q 6 :

The product (C) in the below-mentioned reaction is: [2024]

Q 8 :

Identify the correct set of reagents or reaction conditions 'X' and 'Y' in the following set of transformation. [2024]

Q 9 :

Product P is [2024]

Q 10 :

Identify the major product in the following reaction. [2024]

Q 11 :

Consider the above chemical reaction product ''A'' is: [2024]

Q 12 :

Which among the following compounds will undergo fastest $S_{N} 2$ reaction? [2024]

Q 14 :

In the following sequence of reaction, the major products B and C respectively are: [2024]

Q 15 :

In the above reaction product 'P' is [2024]

Q 16 :

The total number of hydrogen atoms in product A and product B is _____. [2024]

Q 17 :

Given below are two statements: [2025]

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

Q 18 :

Given below are two statements: [2025]

In the light of the above statements, choose the correct answer from the options given below.

Q 19 :

The structure of the major product formed in the following reaction is: [2025]

Q 20 :

The ascending order of relative rate of solvolysis of following compounds is: [2025]

Q 21 :

The products A and B in the following reactions, respectively, are: [2025]

$A \overset{Ag - {NO}_{2}}{\to} {CH}_{3} - {CH}_{2} - {CH}_{2} - Br \overset{AgCN}{\to} B$

Q 22 :

The product B formed in the following reaction sequence is: [2025]

Q 23 :

The major product of the following reaction is: [2025]

Q 24 :

In the following substitution reaction: [2025]

Product ‘P’ formed is:

Q 26 :

For the reaction

${RCH}_{2} Br + I^{-} \overset{Acetone}{\to} \underset{Major}{{RCH}_{2} I} + {Br}^{-}$

The correct statement is [2023]

Q 27 :

Choose the halogen which is most reactive towards $S_{N} 1$ reaction in the given compounds (A, B, C and D) [2023]

Q 28 :

Identify the correct order of reactivity for the following pairs towards the respective mechanism. [2023]

Choose the correct answer from the options given below:

Q 29 :

Compound from the following that will not produce precipitate on reaction with ${AgNO}_{3}$ is: [2023]

Q 30 :

2-Methyl propyl bromide reacts with $C_{2} H_{5} O^{-}$ and gives 'A' whereas on reaction with $C_{2} H_{5} OH$ it gives 'B'. The mechanism followed in these reactions and the products 'A' and 'B' respectively are: [2023]

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Topic Question Set

Q 1 : The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is: [2024]

Q 4 : Which among the following halide/s will not show SN1 reaction: [2024] Choose the most appropriate answer from the options given below:

Q 5 : Alkyl halide is converted into alkyl isocyanide by reaction with: [2024]

Q 6 : The product (C) in the below-mentioned reaction is: [2024]

Q 8 : Identify the correct set of reagents or reaction conditions 'X' and 'Y' in the following set of transformation. [2024]

Q 9 : Product P is [2024]

Q 10 : Identify the major product in the following reaction. [2024]

Q 11 : Consider the above chemical reaction product ''A'' is: [2024]

Q 12 : Which among the following compounds will undergo fastest SN2 reaction? [2024]

Q 14 : In the following sequence of reaction, the major products B and C respectively are: [2024]

Q 15 : In the above reaction product 'P' is [2024]

Q 16 : The total number of hydrogen atoms in product A and product B is _____. [2024]

Q 17 : Given below are two statements: [2025] In the light of the above statements, choose the most appropriate answer from the options given below:

Q 18 : Given below are two statements: [2025] In the light of the above statements, choose the correct answer from the options given below.

Q 19 : The structure of the major product formed in the following reaction is: [2025]

Q 20 : The ascending order of relative rate of solvolysis of following compounds is: [2025]

Q 21 : The products A and B in the following reactions, respectively, are: [2025] A→Ag-NO2CH3-CH2-CH2-Br→AgCNB

Q 22 : The product B formed in the following reaction sequence is: [2025]

Q 23 : The major product of the following reaction is: [2025]

Q 24 : In the following substitution reaction: [2025] Product ‘P’ formed is:

Q 26 : For the reaction RCH2Br+I-→AcetoneRCH2IMajor+Br- The correct statement is [2023]

Q 27 : Choose the halogen which is most reactive towards SN1 reaction in the given compounds (A, B, C and D) [2023]

Q 28 : Identify the correct order of reactivity for the following pairs towards the respective mechanism. [2023] Choose the correct answer from the options given below:

Q 29 : Compound from the following that will not produce precipitate on reaction with AgNO3 is: [2023]

Q 30 : 2-Methyl propyl bromide reacts with C2H5O- and gives 'A' whereas on reaction with C2H5OH it gives 'B'. The mechanism followed in these reactions and the products 'A' and 'B' respectively are: [2023]

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Q 1 :

The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is: [2024]

Q 4 :

Which among the following halide/s will not show $S_{N} 1$ reaction: [2024]

Choose the most appropriate answer from the options given below:

Q 5 :

Alkyl halide is converted into alkyl isocyanide by reaction with: [2024]

Q 6 :

The product (C) in the below-mentioned reaction is: [2024]

Q 8 :

Identify the correct set of reagents or reaction conditions 'X' and 'Y' in the following set of transformation. [2024]

Q 9 :

Product P is [2024]

Q 10 :

Identify the major product in the following reaction. [2024]

Q 11 :

Consider the above chemical reaction product ''A'' is: [2024]

Q 12 :

Which among the following compounds will undergo fastest $S_{N} 2$ reaction? [2024]

Q 14 :

In the following sequence of reaction, the major products B and C respectively are: [2024]

Q 15 :

In the above reaction product 'P' is [2024]

Q 16 :

The total number of hydrogen atoms in product A and product B is _____. [2024]

Q 17 :

Given below are two statements: [2025]

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

Q 18 :

Given below are two statements: [2025]

In the light of the above statements, choose the correct answer from the options given below.

Q 19 :

The structure of the major product formed in the following reaction is: [2025]

Q 20 :

The ascending order of relative rate of solvolysis of following compounds is: [2025]

Q 21 :

The products A and B in the following reactions, respectively, are: [2025]

$A \overset{Ag - {NO}_{2}}{\to} {CH}_{3} - {CH}_{2} - {CH}_{2} - Br \overset{AgCN}{\to} B$

Q 22 :

The product B formed in the following reaction sequence is: [2025]

Q 23 :

The major product of the following reaction is: [2025]

Q 24 :

In the following substitution reaction: [2025]

Product ‘P’ formed is:

Q 26 :

For the reaction

${RCH}_{2} Br + I^{-} \overset{Acetone}{\to} \underset{Major}{{RCH}_{2} I} + {Br}^{-}$

The correct statement is [2023]

Q 27 :

Choose the halogen which is most reactive towards $S_{N} 1$ reaction in the given compounds (A, B, C and D) [2023]

Q 28 :

Identify the correct order of reactivity for the following pairs towards the respective mechanism. [2023]

Choose the correct answer from the options given below:

Q 29 :

Compound from the following that will not produce precipitate on reaction with ${AgNO}_{3}$ is: [2023]

Q 30 :

2-Methyl propyl bromide reacts with $C_{2} H_{5} O^{-}$ and gives 'A' whereas on reaction with $C_{2} H_{5} OH$ it gives 'B'. The mechanism followed in these reactions and the products 'A' and 'B' respectively are: [2023]