Chemistry Alcohols & Phenols NUMS 2019
PMDC Verified Question 67 of 95
Dehydration of ethanol at 180°C in the presence of conc-\(\text{H}_2\text{SO}_4\) gives
A
Ethene
B
Ethane
C
Ethyne
D
Ether
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Ethene
Concept:

The dehydration of alcohols by concentrated sulfuric acid is highly temperature-dependent.

Formula:

$$ \text{C}_2\text{H}_5\text{OH} \xrightarrow[180^{\circ}\text{C}]{\text{Conc. H}_2\text{SO}_4} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O} $$

Solution:

  • At higher temperatures (170°C - 180°C), an intramolecular dehydration (\(\beta\)-elimination) occurs, stripping water from a single molecule of ethanol to form an alkene.


  • The resulting product is ethene.


Why other options are incorrect:

At lower temperatures (140°C), intermolecular dehydration occurs to form diethyl ether. Ethane and ethyne cannot be formed via simple dehydration of ethanol.

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