A carbon compound when heated in excess of concentrated sulphuric acid at 443K gives ethene. The compound is an________.
alcohol
The question describes a chemical reaction where a carbon compound, upon heating with excess concentrated sulfuric acid ($ \text{H}_2\text{SO}_4 $) at 443K, produces ethene ($ \text{C}_2\text{H}_4 $). We need to identify the type of carbon compound that undergoes this transformation.
Understanding the Dehydration Reaction
The reaction described is a classic example of the dehydration of an alcohol. Concentrated sulfuric acid acts as a strong dehydrating agent and catalyst in this process. It removes a molecule of water ($ \text{H}_2\text{O} $) from the alcohol molecule, leading to the formation of an alkene.
The general reaction for the dehydration of an alcohol to an alkene is:
$$ \text{R-CH}_2\text{-CH(OH)-R'} \xrightarrow{\text{Conc. } \text{H}_2\text{SO}_4, 443\text{K}} \text{R-CH=CH-R'} + \text{H}_2\text{O} $$For the specific product to be ethene ($ \text{CH}_2=\text{CH}_2 $), the starting alcohol must be ethanol ($ \text{CH}_3\text{CH}_2\text{OH} $).
The reaction is specifically:
$$ \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Conc. } \text{H}_2\text{SO}_4, 443\text{K}} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O} $$Ethanol → Ethene + Water
Analyzing the Options
Let's examine why the other options are incorrect:
- Acid: Carboxylic acids generally do not yield alkenes upon heating with concentrated sulfuric acid under these conditions. For example, ethanoic acid ($ \text{CH}_3\text{COOH} $) might form acetic anhydride upon heating with a dehydrating agent, not ethene.
- Ester: Esters are typically formed from alcohols and acids. They undergo reactions like hydrolysis or transesterification, not dehydration to form alkenes. For example, ethyl ethanoate ($ \text{CH}_3\text{COOCH}_2\text{CH}_3 $) would hydrolyze in the presence of acid or base.
- Alkane: Alkanes are saturated hydrocarbons. They are generally less reactive than alcohols and do not undergo dehydration to form alkenes under these conditions. Reactions like cracking occur at much higher temperatures.
Conclusion on Alcohol Dehydration
Based on the known chemical reactions, alcohols are the class of compounds that readily undergo dehydration in the presence of concentrated sulfuric acid at 443K to form alkenes. Since the product is specified as ethene, the starting compound must be ethanol, which is an alcohol.
Therefore, the carbon compound is an alcohol.
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