Question

Which of the following reactions will not produce a racemic product?

Options

• \[\begin{array}{cc}
  \ce{O}\phantom{........}\\
  ||\phantom{........}\\
  \phantom{}\ce{CH3 - C CH2 CH3 ->[HCN]}
  \end{array}\]

• 

• \[\ce{CH3CH2CH = CH2 ->[HBr]}\]

• \[\begin{array}{cc}
  \ce{CH3}\phantom{........}\\
  |\phantom{...........}\\
  \phantom{.}\ce{CH3 - C - CH = CH2 ->[HCl]}\\
  |\phantom{...........}\\
  \ce{H}\phantom{...........}
  \end{array}\]

Answer 1

\[\begin{array}{cc}
\ce{CH3}\phantom{........}\\
|\phantom{...........}\\
\phantom{.}\ce{CH3 - C - CH = CH2 ->[HCl]}\\
|\phantom{...........}\\
\ce{H}\phantom{...........}
\end{array}\]

Explanation:

\[\begin{array}{cc}
\phantom{....................................................................................}\ce{Cl}\\
\phantom{...................................................................................}|\\
\phantom{}\ce{(CH3)2CH - CH = CH2 ->[HCl] (CH3)2CH - \overset{+}{C}H - CH3 ->[Hydride shift] CH3 - \overset{+}{C} - CH2 - CH3 -> CH3 - C - CH2 - CH3}\\
\phantom{.........................................................}|\phantom{...........................}|\phantom{.}\\
\phantom{............................................................}\ce{CH3}\phantom{.......................}\ce{CH3}\phantom{.}
\end{array}\]

There is no chiral carbon in the product of this reaction.