Question

Predict the appearance of the high-resolution proton NMR spectrum of

(a) cyclohexane.

(b) diethyl ether.

(c) 1, 2 - dimethoxyethane, CH₃OCH₂CH₂OCH₃.

Short answer

High-resolution NMR spectroscopy is a universal analytical tool that can provide precise knowledge on chemical shifts, J coupling constants, multiplet patterns, and relative peak areas.

Step-by-step solution

Part(a) Step 1: Given information

We need to predict the appearance of the high resolution proton NMR spectrum of cyclohexane.

Part(a) Step 2: The structure of cyclohexane 

The methylene collections in cyclohexane are similar.

The structure of cyclohexane is given below:

Part (a) Step3: Explain the reason 

Axial and equatorial are the two types of protons in cyclohexane. There is a constant and quick conversion between the chair shapes of cyclohexane. Therefore, only a singlet is acquired at $~1.5\delta$.

The spectrum occurs as shown below:

Part(b) Step 1: Given information

We need to predict the appearance of the high resolution proton NMR spectrum of diethyl ether.

Part(b) Step 2: The structure of diethyl ether 

The structure of diethyl ether is given below:

Part(b) Step 3: Explain the reason 

Set (a) protons are methyl protons, which are additionally connected to an oxygen particle. The methyl protons would occur as a triplet corresponding to $6$protons at$~1.2\delta$.

The spectrum occurs at given below:

Part(c) Step 1: Given information

We need to predict the appearance of the high resolution proton NMR spectrum of$1,2\text{- dimethoxyethane,}{\mathrm{CH}}_3{\mathrm{OCH}}_2{\mathrm{CH}}_2{\mathrm{OCH}}_3\text{.}$

Part(c) Step 2: The structure of dimethoxyethane CH3OCH2CH2OCH3

The structure of$1,2$dimethoxyethane${\mathrm{CH}}_3{\mathrm{OCH}}_2{\mathrm{CH}}_2{\mathrm{OCH}}_3$ is given below:

Part(c) Step 3: Explain the reason 

There are two sets of protons. One is methyl protons, which are separated from the other protons by the neighboring oxygen atom. Therefore, it appears as a singlet corresponding to 6 protons at $~3.2\delta$The other one is methylene protons, which are equivalent and thus, do not couple with each other. The methylene protons are again attached to the electronegative oxygen atom and emerge as a singlet at $~3.4\delta$.The spectrum is shown below: