Q.47 The number of peaks in the 1H NMR spectrum of methoxymethane
(𝐶𝐻3𝑂𝐶𝐻3) is __________.

Methoxymethane (CH₃OCH₃), also known as dimethyl ether, exhibits one peak in its ¹H NMR spectrum due to all six protons being chemically equivalent. This fill-in-the-blank question from CSIR NET Life Sciences/chemistry sections tests understanding of proton environments in symmetric molecules.​

Molecular Structure

Methoxymethane has the formula CH₃-O-CH₃, featuring two identical methyl groups attached to a central oxygen atom. The molecule’s symmetry makes the two CH₃ groups indistinguishable, placing all six hydrogen atoms in the same chemical environment. No distinct proton types exist, unlike in unsymmetric ethers like methoxyethane (CH₃OCH₂CH₃), which shows three peaks from three unique proton environments.​

NMR Peak Analysis

In ¹H NMR, the number of peaks equals the number of unique proton environments based on chemical equivalence. Here, rotation and symmetry ensure all H atoms experience identical shielding from the oxygen, resulting in a single singlet peak around 3.3-3.4 ppm (9H integration). No spin-spin splitting occurs due to the absence of adjacent non-equivalent protons.​

Common Misconceptions

Examinees might predict two peaks, mistaking the methyl groups as distinct like in CH₃CH₂OH (three peaks: CH₃, CH₂, OH). However, methoxymethane lacks such asymmetry—unlike ethanol (3:2:1 ratio) or methyl acetate (two peaks from CH₃-C=O and CH₃-O). Diethyl ether (CH₃CH₂)₂O shows a quartet and triplet from coupled CH₂-CH₃ protons, but dimethyl ether’s lack of α-hydrogens prevents splitting.​

Methoxymethane, or 1H NMR peaks methoxymethane (CH₃OCH₃), is a key topic in organic spectroscopy for CSIR NET aspirants. This symmetric ether produces exactly 1 peak in its proton NMR spectrum because all hydrogens are equivalent.​

Why Only One Peak?

The 1H NMR peaks methoxymethane analysis hinges on chemical equivalence. Both CH₃ groups mirror each other across the oxygen, yielding a single signal (singlet, ~3.3 ppm, 6H). Contrast this with methoxyethane’s three peaks from CH₃ (d), CH₂ (q), and CH₃ (t).​

Exam Relevance

CSIR NET questions like “The number of peaks in the 1H NMR spectrum of methoxymethane (CH₃OCH₃) is __________” test symmetry recognition. Answer: 1. Practice similar: ethanol (3 peaks), acetone (2 peaks).​

Key Takeaways

• Proton environments: 1 (all equivalent).

• Splitting: None (no n+1 rule applies).

• Chemical shift: 3.2-3.4 ppm for -O-CH₃.​

Master 1H NMR peaks methoxymethane for spectroscopy success!​