Organic Chemistry, Books A La Carte Edition (7th Edition)
Organic Chemistry, Books A La Carte Edition (7th Edition)
7th Edition
ISBN: 9780321819031
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Textbook Question
Chapter 14, Problem 43P

In the mass spectrum of the following compounds, which is the tallest—the peak at m/z =57 or the peak at m/z = 71?

  1. a. 3·methylpentane
  2. b. 2·methylpentnne
Expert Solution & Answer
Check Mark
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.

Organic Chemistry, Books A La Carte Edition (7th Edition), Chapter 14, Problem 43P , 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.

Organic Chemistry, Books A La Carte Edition (7th Edition), Chapter 14, Problem 43P , additional homework tip  2

Organic Chemistry, Books A La Carte Edition (7th Edition), Chapter 14, Problem 43P , additional homework tip  3

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 14 Solutions

Organic Chemistry, Books A La Carte Edition (7th Edition)

Ch. 14.6 - Sketch the mass spectrum expected for...Ch. 14.6 - The mass spectra of 1-methoxybutane,...Ch. 14.6 - Prob. 14PCh. 14.6 - Identify the ketones responsible for the mass...Ch. 14.6 - Prob. 16PCh. 14.6 - Using curved arrows, show the principal fragments...Ch. 14.6 - The reaction of (Z)-2-pentene with water and a...Ch. 14.9 - Prob. 19PCh. 14.9 - Prob. 20PCh. 14.9 - Prob. 21PCh. 14.13 - Prob. 22PCh. 14.14 - Which occur at a larger wavenumber: a. the C O...Ch. 14.14 - Prob. 24PCh. 14.14 - Prob. 25PCh. 14.14 - Rank the following compounds from highest...Ch. 14.14 - Which shows an O H stretch at a larger...Ch. 14.15 - Prob. 28PCh. 14.15 - a. An oxygen-containing compound shows an...Ch. 14.15 - Prob. 30PCh. 14.15 - For each of the following pair of compounds, name...Ch. 14.16 - Which of the following compounds has a vibration...Ch. 14.16 - Prob. 33PCh. 14.17 - A compound with molecular formula C4H6O gives the...Ch. 14.19 - Prob. 35PCh. 14.19 - Prob. 36PCh. 14.20 - Predict the max of the following compound:Ch. 14.20 - Prob. 38PCh. 14.21 - a. At pH = 7 one of the ions shown here is purple...Ch. 14.21 - Prob. 40PCh. 14.22 - Prob. 41PCh. 14.22 - Prob. 42PCh. 14 - In the mass spectrum of the following compounds,...Ch. 14 - Prob. 44PCh. 14 - For each of the following pairs of compounds,...Ch. 14 - Draw structures for a saturated hydrocarbon that...Ch. 14 - a. How could you use IR spectroscopy to determine...Ch. 14 - Assuming that the force constant is approximately...Ch. 14 - In the following boxes, list the types of bonds...Ch. 14 - A mass spectrum shows significant peaks at m/z. =...Ch. 14 - Prob. 51PCh. 14 - Prob. 52PCh. 14 - Prob. 53PCh. 14 - How can you use UV spectroscopy to distinguish...Ch. 14 - Rank the following compounds from highest...Ch. 14 - Rank the following compounds from highest...Ch. 14 - What peaks in their mass spectra can be used to...Ch. 14 - Each of the IR spectra shown below is accompanied...Ch. 14 - Prob. 59PCh. 14 - Prob. 60PCh. 14 - How can IR spectroscopy distinguish between...Ch. 14 - 62. Draw the structure of a carboxylic acid that...Ch. 14 - Prob. 63PCh. 14 - Give approximate wavenumbers for the major...Ch. 14 - Prob. 65PCh. 14 - Prob. 66PCh. 14 - Prob. 67PCh. 14 - The IR spectrum of a compound with molecular...Ch. 14 - Which one of the following live compounds produced...Ch. 14 - Prob. 70PCh. 14 - Phenolphthalein is an acid-base indicator. In...Ch. 14 - Which one of the following five compounds produced...Ch. 14 - The IR and mass spectra for three different...
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