Question

Given below are two statements: 
Statement (I): Alcohols are formed when alkyl chlorides are treated with aqueous potassium hydroxide by elimination reaction. 
Statement (II): In alcoholic potassium hydroxide, alkyl chlorides form alkenes by abstracting the hydrogen from the $ \beta $-carbon. 
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are incorrect
• B. Statement I is incorrect but Statement II is correct
• C. Statement I is correct but Statement II is incorrect
• D. Both Statement I and Statement II are correct

Hint:

Elimination and substitution reactions are key processes for forming alkenes and alcohols, respectively, based on the conditions (e.g., solvent, temperature).

Answer 1

The Correct Option is B

To solve this question, we need to analyze the given statements regarding the reactions of alkyl chlorides with potassium hydroxide solutions.

1. Understanding Statement I:
   • It states that alcohols are formed by treating alkyl chlorides with aqueous potassium hydroxide through an elimination reaction.
   • This statement is incorrect. Alcohols are indeed formed from alkyl chlorides by the action of aqueous potassium hydroxide, but this happens via a substitution reaction, not an elimination reaction. The hydroxide ion (\( \text{OH}^- \)) replaces the chloride ion (\( \text{Cl}^- \)) to form alcohols.
   • The reaction follows: \(R-\text{Cl} + \text{KOH(aq)} \rightarrow R-\text{OH} + \text{KCl}\)
2. Understanding Statement II:
   • It suggests that alkyl chlorides form alkenes in the presence of alcoholic potassium hydroxide by abstracting hydrogen from the \( \beta \)-carbon.
   • This statement is correct. When alkyl chlorides are treated with alcoholic KOH, elimination occurs forming alkenes. The reaction is known as a dehydrohalogenation reaction, where the hydrogen from the β-carbon is abstracted, and a double bond is formed.
   • The reaction follows: \(R-\text{CH}_2-\text{CHCl}-R' + \text{KOH(alc)} \rightarrow R-\text{CH}=\text{CH}-R' + \text{KCl} + \text{H}_2\text{O}\)

Based on the above explanations:

• Statement I is incorrect because it confuses elimination with substitution in the formation of alcohols.
• Statement II is correct as it properly describes the elimination process forming alkenes.

Thus, the most appropriate option is: Statement I is incorrect but Statement II is correct.

Answer 2

To answer this question, let's evaluate each statement regarding the chemical reactions involving alkyl chlorides and potassium hydroxide:

1. Statement I: Alcohols are formed when alkyl chlorides are treated with aqueous potassium hydroxide by elimination reaction.

Explanation: Alkyl chlorides, when reacted with aqueous potassium hydroxide (\( \text{KOH (aq)} \)), undergo a nucleophilic substitution reaction (not an elimination reaction) to form alcohols. In this process, the hydroxide ion (\( \text{OH}^- \)) from the aqueous KOH replaces the chlorine atom (\( \text{Cl} \)) in the alkyl chloride, resulting in the formation of an alcohol. This is known as a nucleophilic substitution reaction (S_N1 or S_N2), not an elimination reaction. Therefore, Statement I is incorrect.

1. Statement II: In alcoholic potassium hydroxide, alkyl chlorides form alkenes by abstracting the hydrogen from the \( \beta \)-carbon.

Explanation: When alkyl chlorides are treated with alcoholic potassium hydroxide (\( \text{KOH (alcoholic)} \)), an elimination reaction (E1 or E2) occurs. The \(\text{OH}^-\) ion acts as a base and abstracts a hydrogen atom from the \( \beta \)-carbon in the alkyl chloride. This results in the formation of a double bond, leading to the creation of an alkene by eliminating hydrogen chloride (\( \text{HCl} \)). Therefore, Statement II is correct.

After analyzing both statements, we conclude that:

• Statement I is incorrect because it inaccurately describes the reaction mechanism leading to the formation of alcohols from alkyl chlorides.
• Statement II is correct because it accurately describes the elimination reaction mechanism in the presence of alcoholic KOH.

Conclusion: Thus, the most appropriate answer is: Statement I is incorrect but Statement II is correct.