Which of the following molecules can form hydrogen bonding interactions with themselves in a pure sample?

• A. CH3OH
• B. C2H6
• C. CO2
• D. CH4

Answer: (A)

Verified step by step guidance

1. Identify the key requirement for hydrogen bonding: a molecule must have a hydrogen atom directly bonded to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F).
2. Examine each molecule to see if it contains an N-H, O-H, or F-H bond, which is necessary for hydrogen bonding.
3. For CH3OH (methanol), note that it has an O-H bond, which allows it to form hydrogen bonds with other methanol molecules.
4. For C2H6 (ethane), CO2 (carbon dioxide), and CH4 (methane), observe that none have hydrogen atoms bonded to N, O, or F; thus, they cannot form hydrogen bonds with themselves.
5. Conclude that only CH3OH can form hydrogen bonding interactions with itself in a pure sample due to the presence of the O-H bond.