Which of the following 1H NMR spectra best corresponds to diethyl ether ($C_2{H}_{5}O{C}_2{H}_5$)?

• A. A singlet at $3.4$ ppm (4H) and a triplet at $1.2$ ppm (6H)
• B. A doublet at $7.2$ ppm (2H) and a doublet at $6.8$ ppm (2H)
• C. A quartet at $4.1$ ppm (2H) and a triplet at $1.2$ ppm (3H)
• D. A singlet at $2.1$ ppm (3H) and a singlet at $9.8$ ppm (1H)

Answer: (A)

Verified step by step guidance

1. Identify the structure of diethyl ether, which is \( \mathrm{CH_3CH_2OCH_2CH_3} \). It has two equivalent ethyl groups attached to an oxygen atom.
2. Determine the types of protons present: the methyl protons (\( \mathrm{CH_3} \)) and the methylene protons (\( \mathrm{CH_2} \)) adjacent to the oxygen.
3. Predict the chemical shifts: the methylene protons next to oxygen are deshielded and appear downfield (around 3.4 ppm), while the methyl protons are more shielded and appear upfield (around 1.2 ppm).
4. Analyze the splitting patterns using the n+1 rule: the methylene protons (\( \mathrm{CH_2} \)) are split by the adjacent methyl protons (3 hydrogens), so they appear as a quartet, but since both ethyl groups are equivalent, the signal merges into a singlet or a simplified pattern; the methyl protons (\( \mathrm{CH_3} \)) are split by the adjacent methylene protons (2 hydrogens), resulting in a triplet.
5. Match the integration values: methylene protons correspond to 4 hydrogens (2 groups of \( \mathrm{CH_2} \)) and methyl protons correspond to 6 hydrogens (2 groups of \( \mathrm{CH_3} \)). Therefore, the correct spectrum shows a singlet at 3.4 ppm (4H) and a triplet at 1.2 ppm (6H).