Given below are two statements : Statement I: Et2N-CH2-CH2-Cl will undergo alkaline hydrolysis at a faster rate than Et2CH-CH2-Cl. Statement II: In Et2N-CH2-CH2-Cl, intramolecular substitution takes place first by involving lone pair of electrons on nitrogen. In the light of the above statements, choose the most appropriate answer from the options given below:

Statement I is correct because the nitrogen atom contains a lone pair situated at the beta-position relative to the chlorine atom, promoting Neighboring Group Participation (NGP). Statement II is correct because the lone pair on nitrogen attacks internally to kick out the chloride ion, forming a cyclic aziridinium ion intermediate. This quick intramolecular cyclization leads to an exceptionally rapid hydrolysis rate compared to standard aliphatic substitution. Sees: Nitrogen with lone pair beta to a leaving group. Shortcut: NGP (Neighboring Group Participation) accelerates substitution dramatically via intramolecular assistance. Class 12 Chemistry: Haloalkanes and Haloarenes

Given below are two statements : Statement I: Et2N-CH2-CH2-Cl will undergo alkaline hydrolysis at a faster rate than Et2CH-CH2-Cl. Statement II: In Et2N-CH2-CH2-Cl, intramolecular substitution takes p

Statement I is correct because the nitrogen atom contains a lone pair situated at the beta-position relative to the chlorine atom, promoting Neighboring Group Participation (NGP). Statement II is correct because the lone pair on nitrogen attacks internally to kick out the chloride ion, forming a cyclic aziridinium ion intermediate. This quick intramolecular cyclization leads to an exceptionally rapid hydrolysis rate compared to standard aliphatic substitution. Sees: Nitrogen with lone pair beta

Given below are two statements : Statement I: Et2N-CH2-CH2-Cl will undergo alkaline hydrolysis at a faster rate than Et2CH-CH2-Cl. Statement II: In Et2N-CH2-CH2-Cl, intramolecular substitution takes place first by involving lone pair of electrons on nitrogen. In the light of the above statements, choose the most appropriate answer from the options given below:

Statement I is correct because the nitrogen atom contains a lone pair situated at the beta-position relative to the chlorine atom, promoting Neighboring Group Participation (NGP). Statement II is correct because the lone pair on nitrogen attacks internally to kick out the chloride ion, forming a cyclic aziridinium ion intermediate. This quick intramolecular cyclization leads to an exceptionally rapid hydrolysis rate compared to standard aliphatic substitution. Sees: Nitrogen with lone pair beta to a leaving group. Shortcut: NGP (Neighboring Group Participation) accelerates substitution dramatically via intramolecular assistance. Class 12 Chemistry: Haloalkanes and Haloarenes

Given below are two statements : Statement I: Et2N-CH2-CH2-Cl will undergo alkaline hydrolysis at a faster rate than Et2CH-CH2-Cl. Statement II: In Et2N-CH2-CH2-Cl, intramolecular substitution takes p

Statement I is correct because the nitrogen atom contains a lone pair situated at the beta-position relative to the chlorine atom, promoting Neighboring Group Participation (NGP). Statement II is correct because the lone pair on nitrogen attacks internally to kick out the chloride ion, forming a cyclic aziridinium ion intermediate. This quick intramolecular cyclization leads to an exceptionally rapid hydrolysis rate compared to standard aliphatic substitution. Sees: Nitrogen with lone pair beta

Given below are two statements : Statement I: Et2N-CH2-CH2-Cl will undergo alkaline hydrolysis at a faster rate than…

Year	2026	2025	2024	Total
Questions	11	15	12	38

Q jee_main_2025_29_jan_morning Nucleophilic Aromatic Substitution

In the following substitution reaction:

Nucleophilic Aromatic Substitution diagram for Q34 - JEE Main 2025 Morning — The structural layout depicts a 1,2-dibromo-4-nitrobenzene reacting with sodium ethoxide.

Product

P

formed is:

A.
B.
C.
D.

Solution

Related Formula

Nucleophilic Aromatic Substitution ( $SNAr$ $S_NAr$) occurs via a Meisenheimer complex intermediate, where strong electron-withdrawing groups ( $-NO₂$ $-\mathrm{NO}_2$) activate positions strictly ortho and para to themselves.

Core Logic

The reactant is 1,2-dibromo-4-nitrobenzene. Let us evaluate the two bromine positions relative to the nitro group:

The bromine at C-1 is para to the strong activating $-NO₂$ $-\mathrm{NO}_2$ group.
The bromine at C-2 is meta to the $-NO₂$ $-\mathrm{NO}_2$ group.

Since the para position facilitates effective negative charge delocalization onto the oxygen atoms of the nitro group during intermediate formation, the para-bromine undergoes substitution exclusively by the ethoxide ion ( $^-OC₂H₅$ $^-\mathrm{OC}_2\mathrm{H}_5$). This yields the final product shown below:

Pattern Recognition

In aromatic pathways activated by $-NO₂$ $-\mathrm{NO}_2$, substitution happens exclusively at positions ortho or para relative to the nitro flag; meta positions remain unactivated.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q jee_main_2024_01_february_morning Nucleophilic Substitution

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). 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 statement, choose the most appropriate answer from the options given below:

A. $(A) is correct but (R) is not correct$
B. $Both (A) and (R) are correct but (R) is not the correct explanation of (A)$
C. $(A) is not correct but (R) is correct$
D. $Both (A) and (R) are correct and (R) is the correct explanation of (A)$

Solution

Core Logic

$KCN$ $KCN$ is predominantly ionic and provides cyanide ions ( $CN^-$ $CN^-$) in solution. Although both carbon and nitrogen are in a position to donate electron pairs, the attack takes place mainly through carbon because C-C bond is more stable than C-N bond, forming alkyl cyanides (nitriles) as major product.

KCN + R-X arrow R-CN (Major)

However, $AgCN$ $AgCN$ is mainly covalent in nature and nitrogen is free to donate an electron pair forming isocyanide as the main product.

AgCN + R-X arrow R-NC (Major)

Step 1: Final Conclusion

Assertion (A) is correct. Reason (R) states both are highly ionic, which is incorrect because $AgCN$ $AgCN$ is largely covalent. Therefore, (A) is correct but (R) is not correct.

Pattern Recognition

Ambidentate nucleophile shortcut: Alkali metal cyanides ( $KCN$ $KCN$, $NaCN$ $NaCN$) are ionic $arrow$ $\rightarrow$ attack from Carbon $arrow$ $\rightarrow$ Cyanide. Heavy metal cyanides ( $AgCN$ $AgCN$) are covalent $arrow$ $\rightarrow$ attack from Nitrogen $arrow$ $\rightarrow$ Isocyanide.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q jee_main_2024_01_february_morning Optical Isomerism

Number of optical isomers possible for 2-chlorobutane

Numerical Answer. Answer: 2 to 2

Solution

Core Logic

The structure of 2-chlorobutane is $CH₃-CH(Cl)-CH₂-CH₃$ $CH_3-CH(Cl)-CH_2-CH_3$. There is exactly one chiral center in this molecule, which is the carbon atom at position 2 (bonded to $H$ $H$, $Cl$ $Cl$, $CH₃$ $CH_3$, and $CH₂CH₃$ $CH_2CH_3$).

For a molecule with $n$ $n$ distinct chiral centers and no plane of symmetry, the number of optical isomers (stereoisomers) is $2ⁿ$ $2^n$.

Step 1: Calculate Isomers

Number of chiral centers $n = 1$ $n = 1$. Total optical isomers = $2¹ = 2$ $2^1 = 2$ (one pair of enantiomers: the (R) and (S) configurations).

Optical Isomerism diagram for Q81 - JEE Main 2024 Morning

Pattern Recognition

1 chiral center always gives 2 optical isomers (a pair of enantiomers).

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques

Q79 jee_main_2024_27_jan_morning Nucleophilic Substitution Mechanisms

The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is;

A. Retention occurs in $SN1$ $S_N1$ reaction and inversion occurs in $SN2$ $S_N2$ reaction.
B. Racemisation occurs in $SN1$ $S_N1$ reaction and retention occurs in $SN2$ $S_N2$ reaction.
C. Racemisation occurs in both $SN1$ $S_N1$ and $SN2$ $S_N2$ reactions.
D. Racemisation occurs in $SN1$ $S_N1$ reaction and inversion occurs in $SN2$ $S_N2$ reaction.

Solution

Core Logic

In an $SN1$ $\text{S}_\text{N}1$ pathway, a planar carbocation intermediate is produced. Attack by the nucleophile can take place with equal probability from either side, resulting in complete/partial racemisation. In an $SN2$ $\text{S}_\text{N}2$ pathway, the nucleophile attacks exclusively from the backside opposite the leaving group, causing an absolute structural inversion (Walden inversion).

Pattern Recognition

$SN1 arrow$ $S_N1 \rightarrow$ planar intermediate carbocation $arrow$ $\rightarrow$ Racemisation. $SN2 arrow$ $S_N2 \rightarrow$ direct backside launch $arrow$ $\rightarrow$ Inversion.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q jee_main_2024_29_jan_morning Preparation of Haloarenes

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : Aryl halides cannot be prepared by replacement of hydroxyl group of phenol by halogen atom. Reason R : Phenols react with halogen acids violently. In the light of the above statements, choose the most appropriate from the options given below:

A. $Both A and R are true but R is NOT the correct explanation of A$
B. $A is false but R is true$ $\text{A is false but R is true}$
C. $A is true but R is false$ $\text{A is true but R is false}$
D. $Both A and R are true and R is the correct explanation of A$

Solution

Core Logic

Assertion (A): In phenols, the $C-O$ $C-O$ bond possesses partial double bond character due to resonance (the lone pair of oxygen delocalizes into the benzene ring). Because of this strong $C-O$ $C-O$ bond, nucleophilic substitution reactions where a halide ion would replace the hydroxyl group do not occur under normal conditions. Thus, aryl halides cannot be prepared directly from phenols by reaction with $HX$ $HX$. The statement is True.

Reason (R): Phenols do NOT react violently with halogen acids. In fact, they practically do not react with halogen acids ( $HX$ $HX$) to form aryl halides because the $C-O$ $C-O$ bond is difficult to break. The statement is False.

Step 1: Visualization

Preparation of Haloarenes diagram for Q70 - JEE Main 2024 Morning

Given reason is false.

Step 2: Conclusion

Assertion (A) is correct but Reason (R) is false.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes Class 12 Chemistry: Alcohols Phenols and Ethers

Solution & Explanation

Core Logic

Pattern Recognition

Chapter Mix

Reference Study Guides

More Haloalkanes and Haloarenes Previous-Year Questions — Page 6

Solution

Related Formula

Core Logic

Pattern Recognition

Chapter Mix

Solution

Core Logic

Step 1: Final Conclusion

Pattern Recognition

Chapter Mix

Solution

Core Logic

Step 1: Calculate Isomers

Pattern Recognition

Chapter Mix

Solution

Core Logic

Pattern Recognition

Chapter Mix

Solution

Core Logic

Step 1: Visualization

Step 2: Conclusion

Chapter Mix

More Haloalkanes and Haloarenes Questions — jee_main_2025_28_jan_morning

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