Textbook Question
Propose a structure that corresponds to each spectrum.
(a) <IMAGE>
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15. Analytical Techniques:IR, NMR, Mass Spect
1H NMR:Spin-Splitting Patterns
3:05 minutesProblem 61e
Textbook Question
Draw the signal for the following multiplicities. What is the ratio of peaks within each signal?
(e) sextet
Verified step by step guidance1
Understand the concept of multiplicity in NMR spectroscopy: Multiplicity refers to the splitting pattern of a signal in an NMR spectrum, which is determined by the number of neighboring hydrogen atoms (n) according to the n+1 rule.
Identify the number of neighboring hydrogens: For a sextet, the multiplicity indicates that there are 5 neighboring hydrogens (n = 5), since a sextet is n+1 = 6.
Determine the ratio of peaks: The ratio of peaks in a multiplet is determined by Pascal's triangle. For a sextet, the ratio of peaks is 1:5:10:10:5:1.
Draw the signal: A sextet will have six peaks with the intensity ratio of 1:5:10:10:5:1. This means the outermost peaks are the smallest, and the middle peaks are the largest.
Visualize the signal: When drawing the sextet, ensure that the spacing between the peaks is consistent, and the height of each peak corresponds to the ratio determined in the previous step.
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Video duration:
3mKey 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 between non-equivalent hydrogen atoms. The number of peaks in a signal is determined by the n+1 rule, where n is the number of neighboring hydrogen atoms. Understanding multiplicity is crucial for interpreting NMR spectra and identifying molecular structures.
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Sextet in NMR
A sextet in NMR spectroscopy is a signal split into six peaks. This occurs when a hydrogen atom is coupled with five equivalent neighboring hydrogen atoms (n=5), resulting in a 6-peak pattern. The intensity ratio of these peaks typically follows Pascal's triangle, specifically 1:5:10:10:5:1 for a sextet, reflecting the statistical distribution of spin states.
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Pascal's Triangle in NMR
Pascal's Triangle is used in NMR to predict the relative intensities of peaks in a multiplet. Each row of the triangle corresponds to the coefficients of the binomial expansion, which represent the intensity ratios of the peaks. For example, a sextet's intensity ratio is derived from the sixth row, providing a clear pattern for interpreting complex splitting in NMR spectra.
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