Chemistry · Haloalkanes and haloarenes · chapter 6 of 10

Class 12 Chemistry Chapter 6: Haloalkanes and Haloarenes Assertion-reason questions with answers

2 assertion-reason questions on Haloalkanes and Haloarenes, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): 1-Chloro-3-nitrobenzene is converted to 3-nitrophenol by aqueous NaOH only under conditions about as severe as those for chlorobenzene. Reason (R): A nitro group at the meta position cannot take up, by resonance, the negative charge that develops on the ring when OH⁻ attacks the carbon carrying chlorine.
Show answer

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Attack of OH⁻ puts the negative charge on the carbons ortho and para to the site of attack. A nitro group placed there withdraws and stabilises it; at meta it sits on a carbon that never carries the charge, so it has no activating effect. Both are true and R explains A.

Question 2
Assertion (A): 2-Chloropentane is a chiral molecule. Reason (R): In 2-chloropentane the chlorine is attached to a secondary carbon.
Show answer

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

C-2 of 2-chloropentane carries four different groups (H, CH₃, Cl, CH₂CH₂CH₃), so the molecule is chiral; that carbon is also secondary. Being secondary is not why it is chiral: 3-chloropentane is a secondary halide too but has two identical ethyl groups on C-3 and is achiral.

Take the free Class 12 Chemistry testSee the Class 12 flashcards

← Chapter 5: Coordination CompoundsChapter 7: Alcohols, Phenols and Ethers →