Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+)
Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+)
3rd Edition
ISBN: 9780137533268
Author: Paula Bruice
Publisher: PEARSON+
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Chapter 10, Problem 51P

In the mass spectrum of the following compounds, which would be more intense: the peak at m/z = 57 or the peak at m/z = 71?

  1. a. 3-methylpentane
  2. b. 2-methylpentane
Expert Solution & Answer
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Interpretation Introduction

Interpretation

The tallest peak should be identified.

Explanation of Solution

Mass fragmentation of 3-methyl pentane: In this molecule will be more adopted to lose an ethyl radical forming a secondary carbocation and a primary radical than a methyl radical forming secondary carbocation and methyl radical.  In addition, 3-methylpentane ha undergoes for two path ways to lose an ethyl radical,

Therefore, the peak at m/z=57 would be intense than the peak at m/z=57 , the corresponding fragmentations has shown below.

Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+), Chapter 10, Problem 51P , additional homework tip  1

Mass fragmentation of 2-methyl pentane: The 2-methylpentane has undergoes for pathways to lose a methyl radical in each pathway and it cannot form a secondary carbocation by losing an ethyl radical.  Loss of an ethyl radical would form a primary carbocation and a primary radical. Therefore, it will be more adopt to lose a methyl radical than an ethyl radical, the corresponding peak at m/z=71 would be more intense than the peak at m/z=57.

Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+), Chapter 10, Problem 51P , additional homework tip  2

Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+), Chapter 10, Problem 51P , additional homework tip  3

                    Figure 1

Conclusion

The 3-methyl pentane molecular peak at the m/e=71 has more intense then the peak at m/z=57.

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Chapter 10 Solutions

Pearson eText for Essential Organic Chemistry -- Instant Access (Pearson+)

Ch. 10.6 - Identify the ketone responsible for the mass...Ch. 10.6 - Prob. 13PCh. 10.8 - Prob. 14PCh. 10.8 - Prob. 15PCh. 10.12 - Which will occur at a larger wavenumber: a. a C :...Ch. 10.13 - Which will occur at a larger wavenumber: a. the C...Ch. 10.13 - Prob. 18PCh. 10.13 - Prob. 19PCh. 10.13 - Which will show an O 8 H stretch at a larger...Ch. 10.14 - Prob. 21PCh. 10.14 - Prob. 22PCh. 10.15 - Prob. 23PCh. 10.15 - Prob. 24PCh. 10.17 - Prob. 25PCh. 10.18 - Prob. 26PCh. 10.18 - Prob. 27PCh. 10.19 - Prob. 28PCh. 10.19 - Prob. 29PCh. 10.22 - How many signals would you expect to see in the 1H...Ch. 10.22 - Prob. 31PCh. 10.22 - Prob. 32PCh. 10.23 - Where would you expect to find the 1H NMR signal...Ch. 10.24 - Prob. 34PCh. 10.25 - Prob. 35PCh. 10.25 - Prob. 36PCh. 10.25 - Prob. 37PCh. 10.26 - Prob. 38PCh. 10.26 - Which of the following compounds is responsible...Ch. 10.27 - Prob. 40PCh. 10.27 - Prob. 41PCh. 10.27 - The 1H NMR spectra of two carboxylic acids with...Ch. 10.28 - Prob. 43PCh. 10.28 - Prob. 44PCh. 10.28 - Prob. 45PCh. 10.28 - Describe the 1H NMR spectrum you would expect for...Ch. 10.28 - Identify the compound with molecular formula...Ch. 10.29 - Prob. 48PCh. 10.29 - Prob. 49PCh. 10.29 - Identify the compound with a molecular formula of...Ch. 10 - In the mass spectrum of the following compounds,...Ch. 10 - For each of the following pairs of compounds,...Ch. 10 - Draw the structure of a saturated hydrocarbon that...Ch. 10 - Prob. 54PCh. 10 - Prob. 55PCh. 10 - How could you use UV spectroscopy to distinguish...Ch. 10 - Prob. 57PCh. 10 - Predict the relative intensities of the molecular...Ch. 10 - Prob. 59PCh. 10 - List the following compounds in order from highest...Ch. 10 - How can 1H NMR be used to prove that the addition...Ch. 10 - There are four esters with molecular formula...Ch. 10 - Prob. 63PCh. 10 - Prob. 64PCh. 10 - Each of the IR spectra presented here is...Ch. 10 - Prob. 66PCh. 10 - Five compounds are shown for each of the following...Ch. 10 - Prob. 68PCh. 10 - Prob. 69PCh. 10 - Phenolphthalein is an acidbase indicator. In...Ch. 10 - Which one of the following five compounds produced...Ch. 10 - Prob. 72PCh. 10 - Prob. 73PCh. 10 - Prob. 74PCh. 10 - How could 1H NMR distinguish between the compounds...Ch. 10 - Prob. 76PCh. 10 - Prob. 77PCh. 10 - The 1H NMR spectra of three isomers with molecular...Ch. 10 - The 1H NMR spectra of three isomers with molecular...Ch. 10 - Identify the following compounds. (Relative...Ch. 10 - An alkyl halide reacts with an alkoxide ion to...Ch. 10 - Determine the structure of a compound with...
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