Organic Chemistry
9th Edition
ISBN: 9781305080485
Author: John E. McMurry
Publisher: Cengage Learning
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Chapter 12.SE, Problem 15AP
Write molecular formulas for compounds that show the following molecular ions in their high-resolution mass spectra, assuming that C, H, N, and O might be present. The exact
(a) M+=98.0844
(b) M+=123.0320
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ISTRY EXAM
A Chemistry student performed an experiment on the preparation and identification of an ester. He was given
solutions of a carboxylic acid and an alcohol. He then prepared the ester as per laboratory instruction and
identified the odour of the ester as a pear flavour.
A carboxylic acid has empirical formula CH,O, and its structure is determined by using various spectroscopic
techniques.
(a) The mass spectrum for this carboxylic acid molecule is given below.
100-
80-
60-
relative
intensity
40-
20-
10 15 20 25 30 35 40 45 50 55 60 65 70 75
mass/charge (m/e)
(i) State the relative molecular mass of this molecule; hence determine its molecular formula.
(ii) Draw the structural formula of the carboxylic acid and give its systematic name.
ark
(b) Use the information provided by its Infrared spectrum below to answer the following questions
100
In the mass spectrum of an unknown organic
compound, the molecular ion had a relative
abundance of 19.0 while the M+1 had a relative
abundance of 1.5.
Estimate the number of carbons in the molecule.
1
4
7
2
LO
5
8
carbons
3
6
9
X
C
14. Shown below are the mass spectra (without data tables) of four molecules. (The structure of each
molecule is shown on the spectrum.)
Mark the [M] peak for each, and indicate the molecular weight of the molecule.
Relative Intensity
Relative Intensity
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115-14-5501
0-mm
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=0
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m/z
60
m/z
70
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90 100
Relative Intensity
Relative Intensity
100-
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0
100
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10
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15-NU-5580
15 20 25
115--555
ont
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35 40 45 50 55
m/z
40
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m/z
60
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65 70 75
80
Based on the five mass spectra you have seen, describe how one might identify the [M]*
peak (molecular ion peak) on the mass spectrum of an unknown compound.
Chapter 12 Solutions
Organic Chemistry
Ch. 12.2 - Prob. 1PCh. 12.2 - Two mass spectra are shown in FIGURE 12-8. One...Ch. 12.3 - What are the masses of the charged fragments...Ch. 12.3 - Prob. 4PCh. 12.5 - Prob. 5PCh. 12.5 - Prob. 6PCh. 12.7 - What functional groups might the following...Ch. 12.7 - How might you use IR spectroscopy to distinguish...Ch. 12.8 - Prob. 9PCh. 12.8 - Where might the following compounds have IR...
Ch. 12.8 - Where might the following compound have IR...Ch. 12.SE - Prob. 12VCCh. 12.SE - Show the structures of the fragments you would...Ch. 12.SE - Propose structures for compounds that fit the...Ch. 12.SE - Write molecular formulas for compounds that show...Ch. 12.SE - Camphor, a saturated monoketone from the Asian...Ch. 12.SE - The nitrogen rule of mass spectrometry says that a...Ch. 12.SE - In light of the nitrogen rule mentioned in Problem...Ch. 12.SE - Nicotine is a diamino compound isolated from dried...Ch. 12.SE - The hormone cortisone contains C, H, and O, and...Ch. 12.SE - Halogenated compounds are particularly easy to...Ch. 12.SE - Prob. 22APCh. 12.SE - Propose structures for compounds that fit the...Ch. 12.SE - 2-Methylpentane (C6H14) has the mass spectrum...Ch. 12.SE - Assume that you are in a laboratory carrying out...Ch. 12.SE - What fragments might you expect in the mass...Ch. 12.SE - How might you use IR spectroscopy to distinguish...Ch. 12.SE - Would you expect two enantiomers such as...Ch. 12.SE - Would you expect two diastereomers such as meso-2,...Ch. 12.SE - Propose structures for compounds that meet the...Ch. 12.SE - How could you use infrared spectroscopy to...Ch. 12.SE - Prob. 32APCh. 12.SE - At what approximate positions might the following...Ch. 12.SE - How would you use infrared spectroscopy to...Ch. 12.SE - At what approximate positions might the following...Ch. 12.SE - Assume that you are carrying out the dehydration...Ch. 12.SE - Assume that you are carrying out the base-induced...Ch. 12.SE - Prob. 38APCh. 12.SE - Carvone is an unsaturated ketone responsible for...Ch. 12.SE - Prob. 40APCh. 12.SE - The mass spectrum (a) and the infrared spectrum...Ch. 12.SE - The mass spectrum (a) and the infrared spectrum...Ch. 12.SE - Propose structures for compounds that meet the...Ch. 12.SE - 4-Methyl-2-pentanone and 3-methylpentanal are...Ch. 12.SE - Grignard reagents undergo a general and very...Ch. 12.SE - Ketones undergo a reduction when treated with...Ch. 12.SE - Nitriles, R–=C≡N, undergo a hydrolysis...Ch. 12.SE - The infrared spectrum of the compound with the...Ch. 12.SE - The infrared spectrum of the compound with the...Ch. 12.SE - Prob. 50AP
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