Question

The product (C) in the below mentioned reaction is: \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{Br} \xrightarrow{\text{KOH}_{(alc)} \Delta} A \xrightarrow{\text{HBr}} B \xrightarrow{\text{KOH}_{(alc)}\Delta} C\)
 

• A. Propan-1-ol
• B. Propene
• C. Propyne
• D. Propan-2-ol

Answer 1

The Correct Option is D

To identify product (C) in the given reaction sequence, each step is analyzed:

The initial reaction transforms \(\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{Br}\) (1-bromopropane) into an alkene via dehydrohalogenation using alcoholic KOH and heat. This process eliminates bromine (Br) and a hydrogen atom from an adjacent carbon, yielding propene:

\[\text{CH}_3 - \text{CH}_2 - \text{CH}_2 - \text{Br} \xrightarrow{\text{KOH}_{(alc)} \Delta} \text{CH}_3 - \text{CH} = \text{CH}_2\]

This yields compound A: Propene.

The subsequent step involves the addition of HBr to propene. Markovnikov's rule dictates that the hydrogen atom from HBr adds to the carbon with more hydrogen atoms (the terminal carbon), and the bromine attaches to the other carbon in the double bond, forming 2-bromopropane:

\[\text{CH}_3 - \text{CH} = \text{CH}_2 \xrightarrow{\text{HBr}} \text{CH}_3 - \text{CHBr} - \text{CH}_3\]

This produces compound B: 2-bromopropane.

Finally, 2-bromopropane undergoes another dehydrohalogenation with alcoholic KOH. As a secondary alkyl halide, it will undergo an elimination reaction to form an alkene. In this case, 2-bromopropane is converted back to propene:

\[\text{CH}_3 - \text{CHBr} - \text{CH}_3 \xrightarrow{\text{KOH}_{(alc)} \Delta} \text{CH}_3 - \text{CH} = \text{CH}_2\]

The product of this reaction sequence is again propene. However, given the provided options, if propene is the intended target, there appears to be a discrepancy in the provided correct answer. A direct dehydrohalogenation would not produce propan-2-ol; an incorrect choice may have been made, possibly attempting to correlate reaction efficiency without proper context.

Reviewing the process in light of the provided choices and reactions:

The sequence is logically expected to revert to propene. The inadvertent suggestion of propan-2-ol may stem from incorrect examiner choices, possibly probing knowledge beyond the scope of the presented options.