From the following, choose the ones which are not secondary haloalkanes:
A. 2-Bromobutane
B. 1-Bromo-3-methylbutane
C. 3-Bromopentane
D. 2-Bromo-2-methylpentane
E. 2-Bromo-3-methylbutane
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → B and D only
A haloalkane is primary (1°), secondary (2°) or tertiary (3°) according to the carbon that carries the halogen: a carbon bonded to one, two or three other carbon atoms. Locate the bromine in each compound:
A. 2-Bromobutane — Incorrect. \( \ce{CH3CH(Br)CH2CH3} \): Br is on C-2, bonded to two carbons, so it is secondary.
B. 1-Bromo-3-methylbutane — Correct. \( \ce{BrCH2CH2CH(CH3)2} \): Br is on the end carbon, bonded to one carbon, so it is primary, not secondary.
C. 3-Bromopentane — Incorrect. \( \ce{CH3CH2CH(Br)CH2CH3} \): Br is on C-3, bonded to two carbons, so it is secondary.
D. 2-Bromo-2-methylpentane — Correct. \( \ce{(CH3)2C(Br)CH2CH2CH3} \): Br is on a carbon bonded to three carbons, so it is tertiary, not secondary.
E. 2-Bromo-3-methylbutane — Incorrect. \( \ce{CH3CH(Br)CH(CH3)2} \): Br is on C-2, bonded to two carbons, so it is secondary.
NCERT (2026-27 edition):
Alkyl Halides or Haloalkanes (R—X) – “… If halogen is attached to a primary carbon atom in an alkyl halide, the alkyl halide is called primary alkyl halide or 1° alkyl halide. Similarly, if halogen is attached to secondary or tertiary carbon atom, the alkyl halide is called secondary alkyl halide (2°) and tertiary (3°) alkyl halide, respectively.”