(a) Interpretation: The appearance of the high resolution 13 C spectrum of methyl formate when the protons are not decoupled should be predicted. Concept introduction: 13 C isotope of carbon has low natural abundance. 12 C is the most abundant isotope in nature. But it is NMR inactive because the spin quantum number is zero. Since 13 C is less likely to find in nature there is a very low probability of finding two 13 C nuclei which are close to each other. So there is no observable spin-spin coupling between adjacent carbons in 13 C NMR spectra. But there are 13 C and 1 H coupling which leads to large number of splitting patterns in the spectrum. To obtain simplified 13 C spectrum scientists use a method called broadband decoupling. This technique avoids the C-H coupling signal, so that all carbon signals appear as singlets.

BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213
BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

Solutions

Chapter 19, Problem 19.22QAP
Interpretation Introduction

(a)

Interpretation:

The appearance of the high resolution 13C spectrum of methyl formate when the protons are not decoupled should be predicted.

Concept introduction:

13C isotope of carbon has low natural abundance. 12C is the most abundant isotope in nature. But it is NMR inactive because the spin quantum number is zero. Since 13C is less likely to find in nature there is a very low probability of finding two 13C nuclei which are close to each other. So there is no observable spin-spin coupling between adjacent carbons in 13C NMR spectra. But there are 13C and 1H coupling which leads to large number of splitting patterns in the spectrum. To obtain simplified 13C spectrum scientists use a method called broadband decoupling. This technique avoids the C-H coupling signal, so that all carbon signals appear as singlets.

Interpretation Introduction

(b)

Interpretation:

The appearance of the high resolution 13C spectrum of acetaldehyde when the protons are not decoupled should be predicted.

Concept introduction:

13C isotope of carbon has low natural abundance. 12C is the most abundant isotope in nature. But it is NMR inactive because the spin quantum number is zero. Since 13C is less likely to find in nature there is a very low probability of finding two 13C nuclei which are close to each other. So there is no observable spin-spin coupling between adjacent carbons in 13C NMR spectra. But there are 13C and 1H coupling which leads to large number of splitting patterns in the spectrum. To obtain simplified 13C spectrum scientists use a method called broadband decoupling. This technique avoids the C-H coupling signal, so that all carbon signals appear as singlets.

Interpretation Introduction

(c)

Interpretation:

The appearance of the high resolution 13C spectrum of acetone when the protons are not decoupled should be predicted.

Concept introduction:

13C isotope of carbon has low natural abundance. 12C is the most abundant isotope in nature. But it is NMR inactive because the spin quantum number is zero. Since 13C is less likely to find in nature there is a very low probability of finding two 13C nuclei which are close to each other. So there is no observable spin-spin coupling between adjacent carbons in 13C NMR spectra. But there are 13C and 1H coupling which leads to large number of splitting patterns in the spectrum. To obtain simplified 13C spectrum scientists use a method called broadband decoupling. This technique avoids the C-H coupling signal, so that all carbon signals appear as singlets.

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