How many β-carbon atoms are present in 2-bromobutane?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 2
The carbon carrying the halogen is the α-carbon; every carbon directly bonded to it is a β-carbon.
\( \displaystyle \overset{1}{\ce{CH3}}-\overset{2}{\ce{CH}}(\ce{Br})-\overset{3}{\ce{CH2}}-\overset{4}{\ce{CH3}} \)
C2: carries Br, so it is the α-carbon.
C1: bonded to C2, so it is a β-carbon.
C3: bonded to C2, so it is a β-carbon.
C4: bonded to C3, not to C2, so it is a γ-carbon.
Total: 2 β-carbon atoms (C1 and C3).
NCERT (2026-27 edition):
Location of α and β carbon in a molecule – “Carbon on which halogen atom is directly attached is called α-carbon and the carbon atom adjacent to this carbon is called β-carbon.”