Bond Fission, Electronic Displacement and Hyperconjugation

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JEE Main 2025

LEVELJEE Advanced

Consider the depicted hydrogen (H) in the hydrocarbons given below. The most acidic hydrogen (H) is

With respect to the compounds I-V, choose the correct statement(s).

* Multiple Correct Options

(A)

The acidity of compound I is due to delocalization in the conjugate base.

(B)

The conjugate base of compound IV is aromatic.

(C)

Compound II becomes more acidic, when it has a -NO

_{2}

substituent.

(D)

The acidity of compounds follows the order I > IV > V > II > III.

JEE Advanced 2021

LEVELJEE Advanced

Comprehension Passage

The amount of energy required to break a bond is same as the amount of energy released when the same bond is formed. In gaseous state, the energy required for homolytic cleavage of a bond is called Bond Dissociation Energy (BDE) or Bond Strength. BDE is affected by

s

-character of the bond and the stability of the radicals formed. Shorter bonds are typically stronger bonds. BDEs for some bonds are given below:

H_{3} C - H(g) Cl - Cl(g) H_{3} C - Cl(g) H - Cl(g) ⟶ H_{3} C^{∙} (g) + H^{∙} (g) ⟶ Cl^{∙} (g) + Cl^{∙} (g) ⟶ H_{3} C^{∙} (g) + Cl^{∙} (g) ⟶ H^{∙} (g) + Cl^{∙} (g) Δ H^{\circ} = 105 kcal mol^{- 1} Δ H^{\circ} = 58 kcal mol^{- 1} Δ H^{\circ} = 85 kcal mol^{- 1} Δ H^{\circ} = 103 kcal mol^{- 1}

Question 1:

Correct match of the $C - H$ bonds (shown in bold) in Column J with their BDE in Column K is $Column-J Molecule (P) H -CH(CH_{3})_{2} (Q) H -CH_{2} Ph (R) H -CH=CH_{2} (S) H -C \equiv CH Column-K BDE (kcal mol^{- 1}) (i) 132 (ii) 110 (iii) 95 (iv) 88$

(A)

P -- iii, Q -- iv, R -- ii, S -- i

(B)

P -- i, Q -- ii, R -- iii, S -- iv

(C)

P -- iii, Q -- ii, R -- i, S -- iv

(D)

P -- ii, Q -- i, R -- iv, S -- iii

Question 2:

For the following reaction $CH_{4} (g) + Cl_{2} (g) light CH_{3} Cl(g) + HCl(g)$ the correct statement is

(A)

Initiation step is exothermic with

Δ H^{\circ} = - 58 kcal mol^{- 1}

(B)

Propagation step involving

^{∙} CH_{3}

formation is exothermic with

Δ H^{\circ} = - 2 kcal mol^{- 1}

(C)

Propagation step involving

CH_{3} Cl

formation is endothermic with

Δ H^{\circ} = + 27 kcal mol^{- 1}

(D)

The reaction is exothermic with

Δ H^{\circ} = - 25 kcal mol^{- 1}

JEE Advanced 2015

LEVELJEE Advanced

CHBr_{3}

(B)

CHI_{3}

(C)

CHCl_{3}

(D)

CH(CN)_{3}

JEE Main 2019

LEVELJEE Main

The correct decreasing order for acid strength is

(A)

FCH_{2} COOH > NCCH_{2} COOH > NO_{2} CH_{2} COOH > ClCH_{2} COOH

(B)

CNCH_{2} COOH > O_{2} NCH_{2} COOH > FCH_{2} COOH > ClCH_{2} COOH

(C)

NO_{2} CH_{2} COOH > NCCH_{2} COOH > FCH_{2} COOH > ClCH_{2} COOH

(D)

NO_{2} CH_{2} COOH > FCH_{2} COOH > CNCH_{2} COOH > ClCH_{2} COOH

JEE Main 2006

LEVELJEE Main

The increasing order of stability of the following free radicals is

(A)

(CH_{3})_{2} \dot{C} H < (CH_{3})_{3} \dot{C} < (C_{6} H_{5})_{2} \dot{C} H < (C_{6} H_{5})_{3} \dot{C}

(B)

(C_{6} H_{5})_{3} \dot{C} < (C_{6} H_{5})_{2} \dot{C} H < (CH_{3})_{3} \dot{C} < (CH_{3})_{2} \dot{C} H

(C)

(C_{6} H_{5})_{2} \dot{C} H < (C_{6} H_{5})_{3} \dot{C} < (CH_{3})_{3} \dot{C} < (CH_{3})_{2} \dot{C} H

(D)

(CH_{3})_{2} \dot{C} H < (CH_{3})_{3} \dot{C} < (C_{6} H_{5})_{3} \dot{C} < (C_{6} H_{5})_{2} \dot{C} H

JEE Main 2021

LEVELJEE Main

The correct order of acid character of the following compounds is

The correct order of increasing acid strength of the compounds is

The strongest acid amongst the following compounds is

(A)

CH_{3} COOH

(B)

HCOOH

(C)

CH_{3} CH_{2} CH(Cl)CO_{2} H

(D)

ClCH_{2} CH_{2} CH_{2} COOH

JEE Main 2021

LEVELJEE Main

Choose the correct statement regarding the formation of carbocations A and B.

(A)

Carbocation B is more stable and formed relatively at faster rate.

(B)

Carbocation A is more stable and formed relatively at slow rate.

(C)

Carbocation B is more stable and formed relatively at slow rate.

(D)

Carbocation A is more stable and formed relatively at faster rate.

JEE Main 2017

LEVELJEE Main

Which of the following molecules is least resonance stabilised?

Which among the following is the strongest acid ?

(A)

CH_{3} CH_{2} CH_{2} CH_{3}

The order of stability of the following carbocations

Arrange the following labelled hydrogens in decreasing order of acidity

In the anion, $HCOO^{-}$ , the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?

(A)

Electronic orbits of carbon atom are hybridised

(B)

The

C = O

bond is weaker than the

C - O

bond

(C)

The anion,

HCOO^{-}

has two resonating structures

(D)

The anion is obtained by removal of a proton from the acid molecule

JEE Main 2020

LEVELJEE Main

Which one of the following compounds possesses the most acidic hydrogen?

The correct order of stability for the following alkoxides is

Which of the following compounds does not exhibit resonance ?

(A)

CH_{3} CH_{2} OCH = CH_{2}

(B)

null

(C)

CH_{3} CH_{2} CH_{2} CONH_{2}

(D)

CH_{3} CH_{2} CH = CHCH_{2} NH_{2}

JEE Main 2021

LEVELJEE Main

Which one among the following resonating structures is not correct ?

Due to the presence of an unpaired electron, free radicals are

Consider the depicted hydrogen (H) in the hydrocarbons given below. The most acidic hydrogen (H) is

With respect to the compounds I-V, choose the correct statement(s).

Comprehension Passage

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } For the following reaction CH4​(g)+Cl2​(g)light​CH3​Cl(g)+HCl(g) the correct statement is

The number of resonance structures for N is :

The correct order of acidity for the following compounds is:

The order of basicity among the following compounds is

Among the following, the number of aromatic compound (s) is-

The correct order of acid strength of the following carboxylic acids is -

Which amongst the following is the strongest acid?

The correct decreasing order for acid strength is

The increasing order of stability of the following free radicals is

The correct order of acid character of the following compounds is

The correct order of increasing acid strength of the compounds is

The strongest acid amongst the following compounds is

Choose the correct statement regarding the formation of carbocations A and B.

Which of the following molecules is least resonance stabilised?

Which among the following is the strongest acid ?

The order of stability of the following carbocations

Arrange the following labelled hydrogens in decreasing order of acidity

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } In the anion, HCOO−, the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?

Which one of the following compounds possesses the most acidic hydrogen?

The correct order of stability for the following alkoxides is

Which of the following compounds does not exhibit resonance ?

Which one among the following resonating structures is not correct ?

Due to the presence of an unpaired electron, free radicals are

For the following reaction $CH_{4} (g) + Cl_{2} (g) light CH_{3} Cl(g) + HCl(g)$ the correct statement is

In the anion, $HCOO^{-}$ , the two carbon-oxygen bonds are found to be of equal length. What is the reason for it ?