Question

Which product is not obtained when \( \mathrm{CH_3CH_2OH} \) reacts with \( \mathrm{H_2SO_4} \)?

• A. \( \mathrm{CH_2{=}CH_2} \)
• B. \( \mathrm{CH{\equiv}CH} \)
• C. \( \mathrm{C_2H_5OC_2H_5} \)
• D. \( \mathrm{C_2H_5HSO_4} \)

Hint:

For ethanol with concentrated \( \mathrm{H_2SO_4} \), remember the temperature effect: ethyl hydrogen sulphate at low temperature, diethyl ether at about \( 413 \, \mathrm{K} \), and ethene at about \( 443 \, \mathrm{K} \). Ethyne is not formed in this reaction.

Answer 1

The Correct Option is B

Step 1: Understanding the reaction of ethanol with sulphuric acid.
Ethanol reacts with concentrated sulphuric acid in different ways depending on the temperature. Sulphuric acid acts both as a strong acid and as a dehydrating agent. Therefore, ethanol can give different products under different reaction conditions. Step 2: Products that can actually be formed.
When ethanol reacts with concentrated \( \mathrm{H_2SO_4} \), the following products may be obtained:

• At lower temperature, ethanol forms ethyl hydrogen sulphate, \( \mathrm{C_2H_5HSO_4} \).
• Around \( 413 \, \mathrm{K} \), two molecules of ethanol combine to form diethyl ether, \( \mathrm{C_2H_5OC_2H_5} \).
• Around \( 443 \, \mathrm{K} \), dehydration of ethanol gives ethene, \( \mathrm{CH_2{=}CH_2} \).

So options (A), (C), and (D) are all possible products of ethanol with sulphuric acid. Step 3: Identify the product not formed.
\( \mathrm{CH{\equiv}CH} \), that is ethyne, is not formed directly when ethanol reacts with sulphuric acid. Sulphuric acid can dehydrate ethanol only up to the alkene stage, producing ethene. It does not convert ethanol into an alkyne under these normal reaction conditions. Step 4: Conclusion.
Therefore, the product that is not obtained when ethanol reacts with sulphuric acid is ethyne, \( \mathrm{CH{\equiv}CH} \).
Final Answer:\( \mathrm{CH{\equiv}CH} \).