Organic Chemistry 1 · Infrared evidence
C₄H₁₀O Isomers by IR: 1-Butanol vs Diethyl Ether
Conditions: Neat liquid IR spectra of the two C₄H₁₀O isomers.
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The question
Which IR band distinguishes 1-butanol from diethyl ether?
Reveal the answer and explanation
Answer and explanation
Correct answer A broad O–H band at 3200–3550 cm⁻¹, present only for 1-butanol
Only the alcohol has O–H.
Not this one A strong C–O band near 1100 cm⁻¹, present only for diethyl ether
Both alcohols and ethers show a C–O stretch.
Not this one sp³ C–H bands at 2850–2960 cm⁻¹
Both are saturated and show these bands.
Not this one A C=O band near 1715 cm⁻¹
Neither compound has a carbonyl.
Worked solution
Both isomers have sp³ C–H stretches below 3000 cm⁻¹ and a strong C–O stretch near 1050–1150 cm⁻¹. Only 1-butanol has an O–H bond, which gives a broad hydrogen-bonded band from about 3200 to 3550 cm⁻¹. That band is absent for diethyl ether.
What you'll practice
Choose the IR band that separates an alcohol from an isomeric ether (1-butanol vs diethyl ether).
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