Ethers are class of organic compounds that contain ether group – an oxygen atom connected to two alkyl groups or aryl groups. They have the general formula R – O – R′, where R and R′ represents the alkyl or aryl groups. Ether, like water have a tetrahedral geometry i.e., oxygen is sp3 hybridised. The C – O – C bond angle in ethers is slightly greater than the tetrahedral angle due to repulsive interactions between the two bulky groups when they are attached to oxygen.
Dehydration of alcohol to ethers is catalysed by:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Conc. \(H_2SO_4\) at 413 K
Alcohols lose water in the presence of protic acids such as \( \ce{H2SO4} \). Which product forms depends on the temperature:
\( \displaystyle \ce{2C2H5OH} \xrightarrow[413\ \mathrm{K}]{\text{conc. }\ce{H2SO4}} \ce{C2H5OC2H5 + H2O} \)
\( \displaystyle \ce{C2H5OH} \xrightarrow[443\ \mathrm{K}]{\text{conc. }\ce{H2SO4}} \ce{CH2=CH2 + H2O} \)
At 413 K a protonated alcohol molecule is attacked by a second alcohol molecule (nucleophilic substitution), which gives the ether.
Why the other options are incorrect
Option (2) Hot & NaOH — Incorrect. A base cannot protonate the –OH group, so it does not dehydrate alcohols.
Option (3) Hot & HBr — Incorrect. HBr converts an alcohol into an alkyl bromide (substitution), not into an ether.
Option (4) Hot & HNO3 — Incorrect. Nitric acid is an oxidising agent; it oxidises or nitrates alcohols instead of dehydrating them.
NCERT (2026-27 edition):
Preparation of Ethers – …
