Question:
Observe the following reaction sequence (major product).
\[
\mathrm{CH_3CH_2CH_2Br}
\xrightarrow{\mathrm{HBr}}
Y
\xrightarrow[\text{major}]{\mathrm{alc.\ KOH}}
Z
\]
Correct statement regarding \(Z\) is
Observe the following reaction sequence (major product).
\[
\mathrm{CH_3CH_2CH_2Br}
\xrightarrow{\mathrm{HBr}}
Y
\xrightarrow[\text{major}]{\mathrm{alc.\ KOH}}
Z
\]
Correct statement regarding \(Z\) is
Show Hint
For alkenes, the number of hyperconjugative structures is approximately equal to the number of \(\alpha\)-hydrogen atoms attached to the carbon adjacent to the double bond.
Updated On: Jul 9, 2026
- Number of \(\sigma\) bonds in it is two
- Number of hyperconjugative resonance structures possible for it is 6
- It does not exhibit cis-trans isomerism
- It is the chain isomer of \(X\) \bigskip
Show Solution
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The Correct Option is B
Solution and Explanation
Step 1: Identify \(Y\).
Addition of HBr to propene (Markovnikov addition) gives
\[
Y=\mathrm{CH_3CHBrCH_3}
\]
(2-bromopropane).
Step 2: Identify \(Z\). On treatment with alcoholic KOH, dehydrohalogenation occurs. \[ \mathrm{CH_3CHBrCH_3} \xrightarrow{\mathrm{alc.\ KOH}} \mathrm{CH_3CH=CH_2} \] Thus, \[ Z=\mathrm{CH_3CH=CH_2} \] (propene).
Step 3: Analyse the options.
• Propene contains more than two \(\sigma\)-bonds. Hence incorrect.
• Propene has six \(\alpha\)-hydrogen atoms and therefore six hyperconjugative structures. \checkmark
• Propene cannot show cis-trans isomerism because one double-bonded carbon has two identical hydrogen atoms.
• Propene is not the chain isomer of \(X\).
Step 4: Final conclusion. Hence, the correct statement is \[ \boxed{\text{Number of hyperconjugative resonance structures possible is }6.} \] Therefore, the correct option is \(\boxed{(B)}\).
Step 2: Identify \(Z\). On treatment with alcoholic KOH, dehydrohalogenation occurs. \[ \mathrm{CH_3CHBrCH_3} \xrightarrow{\mathrm{alc.\ KOH}} \mathrm{CH_3CH=CH_2} \] Thus, \[ Z=\mathrm{CH_3CH=CH_2} \] (propene).
Step 3: Analyse the options.
• Propene contains more than two \(\sigma\)-bonds. Hence incorrect.
• Propene has six \(\alpha\)-hydrogen atoms and therefore six hyperconjugative structures. \checkmark
• Propene cannot show cis-trans isomerism because one double-bonded carbon has two identical hydrogen atoms.
• Propene is not the chain isomer of \(X\).
Step 4: Final conclusion. Hence, the correct statement is \[ \boxed{\text{Number of hyperconjugative resonance structures possible is }6.} \] Therefore, the correct option is \(\boxed{(B)}\).
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