Which of the following compounds would give a $1H$ NMR spectrum with a single signal?

• A. ${\mathrm{CH}}_4$ (methane)
• B. ${\mathrm{CH}}_3\mathrm{CH}{2}_{}\mathrm{OH}$ (ethanol)
• C. ${\mathrm{CH}}_3\mathrm{OCH}{3}_{}$ (dimethyl ether)
• D. ${\mathrm{CH}}_3\mathrm{COOH}$ (acetic acid)

Answer: (A)

Verified step by step guidance

1. Understand that a 1H NMR spectrum shows signals corresponding to chemically distinct hydrogen environments in a molecule. Each unique set of equivalent hydrogens produces a separate signal.
2. Analyze methane (CH\4): All four hydrogens are equivalent because methane is tetrahedral and symmetrical, so it will give a single 1H NMR signal.
3. Analyze ethanol (CH\3CH\2OH): It has three different types of hydrogens — the methyl (CH\3), the methylene (CH\2), and the hydroxyl (OH) hydrogens — so it will give multiple signals.
4. Analyze dimethyl ether (CH\3OCH\3): It has two sets of equivalent hydrogens (two methyl groups attached to oxygen), but these methyl groups are equivalent to each other, so it will give one signal for all six hydrogens.
5. Analyze acetic acid (CH\3COOH): It has methyl hydrogens and the acidic proton (OH), which are in different environments, so it will give multiple signals.