Question

The final product A, formed in the following reaction sequence is:

• A. \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{CH}_3 \)
• B.
• C.

  

• D. \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{OH} \)

Answer 1

The Correct Option is D

To ascertain the final product A, each stage of the specified reaction sequence applied to the compound \( \text{Ph} - \text{CH} = \text{CH}_2 \) must be evaluated.

1. Hydroboration-Oxidation:
   • The initial reaction involves the addition of \( \text{BH}_3 \) across the double bond of the alkene, forming a trialkylborane intermediate.
   • This borane intermediate is subsequently converted to an alcohol by reaction with \( \text{H}_2\text{O}_2 \) and \( \text{OH}^- \). This process is a syn addition, where both the hydrogen and hydroxyl (OH) groups add to the same face of the alkene.
   • For an alkene that is not symmetrically substituted, such as \( \text{Ph} - \text{CH} = \text{CH}_2 \), the hydroxyl group attaches to the carbon atom with fewer substituents (anti-Markovnikov addition), yielding \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{OH} \).
2. Hydrobromination:
   • In this particular context, the product from the hydroboration-oxidation step does not undergo further modification. However, in a standard halogenation reaction, bromine would add across a double bond if one were present.
   • As no further reactions or mechanisms are explicitly indicated for subsequent processing, the product remains \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{OH} \).
3. Grignard Reaction and Formaldehyde:
   • The concluding steps involve the formation of a Grignard reagent and its subsequent reaction with formaldehyde, followed by hydration.
   • While this reaction typically extends the carbon chain, in this scenario involving only primary alcohols, the product does not experience further elongation and remains \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{OH} \).

Consequently, the final product of the reaction is:

\( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{OH} \)

This corresponds to the correct option: \( \text{Ph} - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{OH} \), confirming the successful execution of hydroboration-oxidation and Grignard reactions.