Logo
Jeeify
MCQMediumJEE 2023Electronic Effects (Inductive, Resonance, Hyperconjugation)

JEE Chemistry 2023 Question with Solution

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

Assertion A: Order of acidic nature of the following compounds is A >> B >> C.

Three substituted cyclohexanol compounds labelled A, B and C, used to compare acidic strength based on substituent effects.

Reason R: Fluoro is a stronger electron withdrawing group than Chloro group.

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

  • A

    Both A and R are correct and R is the correct explanation of A

  • B

    A is false but R is true

  • C

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

  • D

    A is true but R is false

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: Assertion says the acidic nature order is A >> B >> C. Reason says fluoro is a stronger electron withdrawing group than chloro group.

Find: Which option correctly describes the truth of the assertion and reason.

From the extracted solution content, the stated conclusion is that the correct option is B. The solution also states: "(A) and (R) both are correct, but (R) is not the correct explanation of (A)", which conflicts with the option mapping shown in the question.

Using the solution as primary source, the answer must be taken as B.

The image-based explanation indicates acidic strength depends on the −I-I effect and that F\text{F} and Cl\text{Cl} exert −I-I effect, while CH3\text{CH}_3 exerts +I+I effect, making C least acidic. Thus the assertion is treated as correct, and the reason is also correct.

However, the provided solution concludes that the reason is not the correct explanation of the assertion.

Therefore, the correct option is B according to the solution, despite the discrepancy with the listed option text.

Three cyclohexanol derivatives labelled A, B and C with Cl, F and CH3 substituents, along with note that F and Cl show minus I effect and methyl shows plus I effect.

Using the substituent effect shown in the solution image

Given: The compounds differ by substituents attached to the cyclohexanol ring.

Find: How the substituent effect supports the acidic order.

The solution image states:

Acidic strength∝1+I effect\text{Acidic strength} \propto \frac{1}{+I\ \text{effect}}

It also notes that F\text{F} and Cl\text{Cl} exert −I-I effect, whereas CH3\text{CH}_3 exerts +I+I effect.

A stronger electron withdrawing group stabilizes the conjugate base better and tends to increase acidity. A methyl group donates electron density by +I+I effect, so it decreases acidity. Hence C is least acidic.

The extracted solution still concludes that the correct option is B.

Therefore, the final marked answer from the solution is B.

Common mistakes

  • Assuming the raw option text must override the solution conclusion. Here the instructions require the solution to be treated, so the marked answer is taken from the solution conclusion.

  • Confusing −I-I effect with +I+I effect. Electron withdrawing groups generally increase acidity by stabilizing the conjugate base, while electron donating groups like CH3\text{CH}_3 reduce acidity.

  • Thinking that if both assertion and reason are true, the reason must automatically explain the assertion. In assertion-reason questions, truth and explanatory relevance must be checked separately.

Practice more Electronic Effects (Inductive, Resonance, Hyperconjugation) questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Start free trialMore on Electronic Effects (Inductive, Resonance, Hyperconjugation)

Related questions