Q1. Which wavenumber region shows the O–H stretching vibration in methanol?

A. 1050–1150 cm⁻¹   B. 1700–1750 cm⁻¹   C. 3200–3600 cm⁻¹   D. 600–800 cm⁻¹

Correct answer: C

Explanation: Alcohol O–H stretches appear as a broad peak around 3200–3600 cm⁻¹ due to hydrogen bonding.

Common misconception: Students often confuse alcohol O–H with carboxylic acid O–H, which is even broader and shifted lower (2500–3000 cm⁻¹).

Q2. Methanol shows a strong absorption near 1050 cm⁻¹. What bond causes this?

A. C=O stretch    B. C–O stretch    C. C=C stretch    D. O–H bend

Correct answer: B

Explanation: Alcohols show a C–O stretching vibration typically between 1000–1200 cm⁻¹, and methanol's is around 1050 cm⁻¹.

Common misconception: Students sometimes misidentify this as an O–H bending vibration, but O–H bends occur lower (around 650–750 cm⁻¹).

Q3. Why is the O–H stretch in methanol broad?

A. The molecule contains a carbonyl group

B. Hydrogen bonding causes a range of O–H bond strengths

C. The O–H bond is non‑polar

D. The C–H stretch overlaps with the O–H stretch

Correct answer: B

Explanation: Hydrogen bonding creates a distribution of O–H bond lengths, broadening the absorption.

Common misconception: Some students think broadness means “strong absorption,” but intensity and width are different concepts.

Q4. Which peak would not appear in methanol's IR spectrum?

A. Broad O–H stretch

B. C–O stretch

C. C–H stretch around 2900 cm⁻¹

D. C=O stretch around 1700 cm⁻¹

Correct answer: D

Explanation: Methanol contains no carbonyl group, so it cannot show a C=O stretch.

Common misconception: Students sometimes assume “all oxygen‑containing molecules have C=O,” which is incorrect.

Q5. The C–H stretching region for methanol appears around:

A. 2800–3000 cm⁻¹   B. 1600–1700 cm⁻¹   C. 1000–1200 cm⁻¹   D. 3500–3700 cm⁻¹

Correct answer: A

Explanation: Alkyl C–H stretches appear between 2800–3000 cm⁻¹.

Common misconception: Confusing C–H stretches with O–H stretches, which occur higher and are broader.

Q6. Which statement correctly describes methanol's IR spectrum?

A. It contains a sharp O–H stretch at 3600 cm⁻¹

B. It contains a broad O–H stretch due to hydrogen bonding

C. It contains a strong C=O stretch at 1720 cm⁻¹

D. It contains no C–O stretching vibrations

Correct answer: B

Explanation: Methanol's O–H stretch is broad, not sharp, and it has no carbonyl.

Common misconception: Students often think “all O–H stretches are sharp,” but only free O–H (e.g., gas‑phase alcohols) are sharp.

Q7. Which combination of peaks confirms the presence of an alcohol like methanol?

A. Broad O–H stretch + C–O stretch

B. Sharp O–H stretch + C=O stretch

C. C=O stretch + C=C stretch

D. Broad N–H stretch + C–H stretch

Correct answer: A

Explanation: Alcohols show broad O–H and C–O stretches. Methanol fits this pattern.

Common misconception: Students sometimes think alcohol O–H stretches are sharp like phenols — they are not.

Q8. A student sees a strong peak at 1050 cm⁻¹ and concludes methanol is present. Why might this be incorrect?

A. Only methanol has a C–O stretch

B. Many alcohols and ethers show peaks in this region

C. Methanol has no peaks near 1050 cm⁻¹ D. 1050 cm⁻¹ is a C=O stretch

Correct answer: B

Explanation: The C–O stretch is common to many alcohols and ethers, so methanol cannot be uniquely identified by this peak alone.

Common misconception: Students often assume “one peak = one molecule,” but IR identifies functional groups, not specific compounds.