Question

Consider the following organic compounds:
\[ C_2H_5CHO, \, CH_3COOH, \, C_2H_5OH, \, CH_3COCH_3 \]
Which one of these compounds, when heated at 443 K in excess conc. \(\text{H}_2\text{SO}_4\), forms ethene as its major product? State the role of conc. \(\text{H}_2\text{SO}_4\) in the reaction. Also, write the chemical equation for the chemical reaction involved.

Answer 1

Step 1: Identify the compound yielding ethene
Ethanol (\( C_2H_5OH \)) is the compound that predominantly forms ethene upon heating at 443 K in excess concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)).
This process is classified as a dehydration reaction, specifically the dehydration of ethanol to produce ethene.

Step 2: Function of concentrated sulfuric acid
Concentrated sulfuric acid serves a dual role: it acts as a catalyst and a dehydrating agent. Its function is to abstract water from the ethanol molecule, leading to its decomposition into ethene and water.

Step 3: Reaction chemical equation
The reaction for the dehydration of ethanol to ethene is represented by the following equation:
\[ C_2H_5OH \xrightarrow{\text{conc.} \, \text{H}_2\text{SO}_4, 443 \, \text{K}} C_2H_4 + \text{H}_2\text{O} \]

Step 4: Reaction mechanism explanation
- Heating ethanol with concentrated sulfuric acid at 443 K induces the elimination of a water molecule (\( \text{H}_2\text{O} \)), resulting in the formation of ethene (\( C_2H_4 \)).
- The presence of concentrated sulfuric acid aids in water removal and promotes the formation of the double bond characteristic of ethene.