Concept:In sulfuric acid-catalyzed dehydration, maintaining a "low temperature" (around 140°C) and an excess of the alcohol favors a substitution mechanism over an elimination mechanism.
Formula:$$ 2\text{C}_2\text{H}_5\text{OH} \xrightarrow[140^{\circ}\text{C}]{\text{H}_2\text{SO}_4} \text{C}_2\text{H}_5\text{-O-}\text{C}_2\text{H}_5 + \text{H}_2\text{O} $$
Solution:- The acid protonates one alcohol molecule, making water a good leaving group.
- Because there is an excess of alcohol, a second unprotonated alcohol molecule acts as a nucleophile, attacking the protonated alcohol and displacing water (\(\text{S}_N2\)).
- The resulting symmetrical ether is diethyl ether.
Why other options are incorrect:Ethene is formed at high temperatures (170°C). Dimethyl ether requires starting with methanol. Acetylene requires extreme dehydrogenation/dehalogenation conditions entirely unrelated to this setup.
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