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Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
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All textbooksMullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 61b
Chapter 14, Problem 61b

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?
(b) triplet

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1
Understand that a triplet in NMR spectroscopy arises when a nucleus is coupled to two equivalent protons. This results in the splitting of the signal into three peaks.
Recall the n+1 rule, where n is the number of neighboring protons. For a triplet, n=2, so the signal is split into 3 peaks.
The ratio of the peaks in a triplet is determined by Pascal's triangle, which gives the coefficients for the binomial expansion. For a triplet, the ratio is 1:2:1.
Draw the triplet signal on an NMR spectrum. The central peak will be twice as tall as the outer peaks, reflecting the 1:2:1 ratio.
Label the peaks to indicate their relative intensities, ensuring the central peak is twice the height of the outer peaks, consistent with the 1:2:1 ratio.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

NMR Multiplicity

NMR multiplicity refers to the splitting of NMR signals into multiple peaks due to spin-spin coupling with neighboring non-equivalent protons. The number of peaks in a signal is determined by the n+1 rule, where n is the number of neighboring protons. Understanding multiplicity is crucial for interpreting NMR spectra and identifying molecular structures.
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General NMR Features

Triplet Signal

A triplet in NMR spectroscopy is a signal that splits into three peaks. This occurs when a proton is coupled with two equivalent neighboring protons. The intensity ratio of the peaks in a triplet is typically 1:2:1, reflecting the statistical likelihood of different spin states of the neighboring protons.
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Identifying Proton Signals

Pascal's Triangle

Pascal's Triangle is a mathematical tool used to determine the intensity ratios of peaks in NMR multiplets. Each row of the triangle corresponds to the coefficients of the binomial expansion, which represent the relative intensities of the peaks in a multiplet. For a triplet, the relevant row is 1:2:1, indicating the peak intensity distribution.
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Related Practice
Textbook Question

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?

(d) quintet

595
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Textbook Question

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?

(c) quartet

938
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Textbook Question

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?

(a) doublet

970
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Textbook Question

Predict the splitting pattern for each of the indicated hydrogens in Assessment 15.59.

(f)

1183
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Textbook Question

Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?

(e) sextet

611
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Textbook Question

Predict the splitting pattern for each of the indicated hydrogens in Assessment 15.59.

(e)

1103
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