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Chapter 13
Mass Spectrometry and Infrared Spectroscopy

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13-00CO
Title
 Infrared Spectrum
Caption
 Part of an infrared spectrum of an alcohol showing absorptions in the 2100–5000 cm–1 region.
Notes
 The broad absorption band at 3320 cm–1 is caused by O–H stretching and the multiple absorption bands from 2800 to 3000 cm–1 are caused by C–H stretching.
Keywords
 infrared, spectrum, alcohol, absorption, O-H, C-H
13-01
Title
 Figure 13.1
Caption
 Schematic of a mass spectrometer.
Notes
 The sample is introduced into an evacuated chamber from the left side of the figure. Molecules encounter an intense ionizing beam of electrons traversing the path of the evacuated chamber. This ionizing beam creates cations from the sample molecules. These cations are accelerated forward by charged repeller and accelerating plates. They encounter a curved region where their path is bent by a variable-strength magnetic field. The cations with higher mass-to-charge ratio are deflected less than cations with lower m/z ratio. The cations which have the m/z ratio selected by the magnetic field strength in the curved region are deflected by exactly the right amount to pass through an ion exit slit and register in a collector.
Keywords
 figure, 13.1,schematic, mass, spectrometer
13-02
Title
 Figure 13.2
Caption
 Mass spectrum of pentane.
Notes
 Peaks of interest arise from cations with +1 charge. The heaviest peak with a reasonable abundance is usually the molecular ion. The m/z value of the molecular ion is the same as the molar mass of the sample compound in the mass spectrometer. Low-abundance peaks up to several m/z units heavier than the molecular ion arise due to the presence of isotopes of various atoms in many of the molecules being analyzed. The base peak is the peak caused by the most stable or kinetically accessible cation in the ion stream. It typically is significantly more abundant than the molecular ion.
Keywords
 figure, 13.2, mass, spectrum, pentane
13-03
Title
 Figure 13.3
Caption
 Mass spectrum of 2-methylbutane.
Notes
 The large peak at m/z = 57 is due to loss of methyl radical to form a secondary carbocation.
Keywords
 figure, 13.3, mass, spectrum, 2-methylbutane
13-04
Title
 Figure 13.4
Caption
 Mass spectrum of 1-bromopropane.
Notes
 The peaks at m/z = 122 is the molecular ion (M). The peak at 122 is caused by molecules containing bromine-79, and the peak at 124 (M + 2) is caused by molecules containing bromine-81. Both of these peaks have about the same intensity because bromine's two major isotopes have about equal abundance.
Keywords
 figure, 13.4, mass, spectrum, 1-bromopropane
13-05
Title
 Figure 13.5
Caption
 Mass spectrum of 2-chloropropane.
Notes
 The molecular ion is found at m/z = 78. The M + 2 peak at 80 is 1/3 of the intensity of M, which is characteristic of chlorinated compounds. All fragments containing chlorine show pairs of peaks, with the heavier peak falling 2 m/z units heavier than the lighter peak, and having 1/3 the intensity of the lighter peak (i.e., m/z = 63 and 65).
Keywords
 figure, 13.5, mass, spectrum, 2-chloropropane
13-06
Title
 Figure 13.6
Caption
 Mass spectrum of sec-butyl isopropyl ether.
Notes
 The peak at m/z = 43 is due to isopropyl cation, the peak at 57 is due to isobutyl cation, the peak at 87 is due to loss of ethyl from the molecular ion, and the peak at 101 is due to loss of methyl. M is at m/z = 116.
Keywords
 figure, 13.6, mass, spectrum, sec-butyl, isopropyl, ether
13-07a-c
Title
 Figure 13.7
Caption
 Mass spectra for Problem 8.
Notes
 Compound a is 2-methoxy-2-methylpropane, b is 2-methylbutane, and c is 1-methylbutane.
Keywords
 figure, 13.7, mass, spectra, 2-methoxy-2-methylpropane, 2-methylbutane, 1-methylbutane
13-08
Title
 Figure 13.8
Caption
 Mass spectrum of 2-hexanol.
Notes
 The peak at m/z = 45 is due to loss of n-butyl, the peak at 84 is due to loss of water, the peak at 87 is due to loss of methyl, and the peak at 102 is M.
Keywords
 figure, 13.8, mass, spectrum, 2-hexanol
13-09a,b
Title
 Figure 13.9
Caption
 Mass spectra for Problem 11.
Notes
 a is 2-pentanone and b is 3-pentanone.
Keywords
 figure, 13.9, 2-pentanone, 3-pentanone
13-10a,b
Title
 Figure 13.10
Caption
 Mass spectra for Problem 13.
Notes
 a is 3-pentanol and b is 2-pentanol.
Keywords
 figure, 13.10, 3-pentanol, 2-pentanol
13-11
Title
 Figure 13.11
Caption
 The electromagnetic spectrum.
Notes
 The three bands of radiation most useful to organic structure elucidation are the ultraviolet band (UV), the infrared band (IR), and the radio-wave band (NMR).
Keywords
 figure, 13.11, electromagnetic, spectrum
13-11-01UN
Title
 Wavelength
Caption
 Drawing of a wave showing how a wavelength is measured.
Notes
 Wavelength and frequency are inversely proportional to each other.
Keywords
 wavelength, frequency, wave
13-11-02UN
Title
 Stretching Vibration
Caption
 Ball-and-spring model of HCl showing a stretching vibration.
Notes
 Stretching or bending vibrations which change the dipole moment of a molecule are infrared-active.
Keywords
 stretching, vibration, ball-and-spring, HCl
13-13
Title
 Figure 13.13
Caption
 The infrared spectrum of 4-hydroxy-4-methyl-2-pentanone.
Notes
 The IR absorptions which cause O–H stretch and C=O stretch are shown in the figure.
Keywords
 figure, 13.13, infrared, 4-hydroxy-4-methyl-2-pentanone
13-14a,b
Title
 Figure 13.14
Caption
 The IR spectra of 2-pentanol and 3-pentanol.
Notes
 The functional-group region (4000–1400 cm–1) is similar for both compounds but the fingerprint region (1400–600 cm–1) differs for the two compounds.
Keywords
 figure, 13.14, 2-pentanol, 3-pentanol
13-14-01T04
Title
 Table 13.4 Important IR stretching frequencies
Caption
 Important IR stretching frequencies.
Notes
 Stretching frequencies and relative intensities of bands associated with stretching vibrations of various types of bonds.
Keywords
 table, 13.4, IR, stretching, frequencies
13-14-02UN
Title
 Polarity vs. IR Absorption Intensity
Caption
 Relative polarities and intensities of IR absorption associated with O–H, N–H, and C–H bonds.
Notes
 As the polarity of a bond increases, the intensity of the IR stretching band associated with it increases.
Keywords
 polarity, bond, IR, intensity
13-15
Title
 Figure 13.15
Caption
 IR spectrum of 2-pentanone.
Notes
 The carbonyl band at 1720 cm–1 is shown. Aldehydes and ketones have strong C=O stretching bands in this region.
Keywords
 figure, 13.15, 2-pentanone, carbonyl
13-16
Title
 Figure 13.16
Caption
 The IR spectrum of 2-cyclohexenone.
Notes
 The pi electrons in the C=O bond are delocalized, giving the C=O bond less double-bond character than an isolated carbonyl group. This results in a looser C=O bond and a lower stretching frequency (1680 cm–1) than an isolated carbonyl group (1720 cm–1).
Keywords
 figure, 13.16, IR, spectrum, 2-cyclohexenone
13-17
Title
 Figure 13.17
Caption
 The IR spectrum of N,N-dimethylpropanamide.
Notes
 The carbonyl group of an amide (C=O stretch 1660 cm–1) has less double-bond character than either the carbonyl group of an isolated ketone (C=O stretch 1720 cm–1) or the carbonyl group of an a,b-unsaturated ketone (C=O stretch 1680 cm–1), so it has a lower frequency than either of these kinds of carbonyl groups.
Keywords
 figure, 13.17, IR, spectrum, dimethylpropanamide
13-18
Title
 Figure 13.18
Caption
 The IR spectrum of ethyl butanoate.
Notes
 Carbonyls in esters have higher stretching frequencies (1740 cm–1) than carbonyls in ketones (1720 cm–1).
Keywords
 figure, 13.18, IR, spectrum, ethyl, butanoate
13-19
Title
 Figure 13.19
Caption
 The IR spectrum of 1-hexanol.
Notes
 In alcohols the C–O stretch shows up at 1060 cm–1.
Keywords
 figure, 13.19, IR, spectrum, 1-hexanol
13-20
Title
 Figure 13.20
Caption
 The IR spectrum of pentanoic acid.
Notes
 Typical carboxylic acids have a carbonyl stretch at 1740 cm–1, a broad O–H stretch from 2600–3400 cm–1, and an O–H stretch at 1220 cm–1.
Keywords
 figure, 13.20, IR spectrum, pentanoic, acid
13-21
Title
 Figure 13.21
Caption
 The IR spectrum of methylcyclohexane.
Notes
 Figure shows frequencies of C–H stretch of an sp3-hybridized C–H bond, and frequencies of C–H bending and CH3–C bending absorptions.
Keywords
 figure, 13.21, IR, methylcyclohexane
13-22
Title
 Figure 13.22
Caption
 The IR spectrum of cyclohexene.
Notes
 The figure shows the frequencies of sp2-hybridized C–H stretching absorptions, sp3-hybridized stretching absorptions, C=C stretching absorptions, and C–H bending absorptions.
Keywords
 figure, 13.22, IR, cyclohexene
13-23
Title
 Figure 13.23
Caption
 The IR spectrum of ethylbenzene.
Notes
 The figure shows the frequencies of aromatic C–C stretching absorptions, C–H bending absorptions, and CH3–C bending absorptions.
Keywords
 figure, 13.23, IR, ethylbenzene
13-24
Title
 Figure 13.24
Caption
 The IR spectrum of pentenal.
Notes
 The C–H stretching vibrations of aldehydic hydrogens show up at 2820 and 2720 cm–1.
Keywords
 figure, 3.24, IR, pentenal
13-25
Title
 Figure 13.25
Caption
 The IR spectrum of isopentylamine.
Notes
 N–H stretching vibrations absorb at about 3400 cm–1 and an isopropyl group shows a double peak at 1380 cm–1.
Keywords
 figure, 13.25, IR, isopentylamine
13-26
Title
 Figure 13.26
Caption
 The IR spectrum of diethyl ether.
Notes
 Ethers show strong absorptions due to C–O stretch at 1100 cm–1 and no other bands characteristic of oxygen-containing functional groups.
Keywords
 figure, 13.26, IR, ether
13-27
Title
 Figure 13.27
Caption
 The mass spectrum for Problem 28.
Notes
 Mass spectrum of trans-2-hexene showing M at m/z = 84 and peaks for loss of methyl, ethyl, and propyl groups.
Keywords
 figure, 13.27, mass, spectrum, problem, 28
13-28
Title
 Figure 13.28
Caption
 The IR spectrum for Problem 28.
Notes
 IR spectrum of trans-2-hexene showing trans C–H bend at 970 cm–1.
Keywords
 figure, 13.28, IR, problem, 28
13-29
Title
 Figure 13.29
Caption
 Infrared spectrum of Compound 1.
Notes
 Compound is 2-methyl-1-pentene. The absorptions in the 3100 and 2900 cm–1 regions show both sp2 and sp3 C–H stretching. The band at 1650 cm–1 shows alkene C=C stretch, the absence of bands at 1500 and 1600 cm–1 show the absence of aromatic C–H bonds, the absorption at 890 cm–1 is characteristic of a disubstituted terminal alkene, and the absence of a band at 720 cm–1 shows that there are less than four connected methylenes.
Keywords
 figure, 13.29, 2-methyl-1-pentene, IR
13-30
Title
 Figure 13.30
Caption
 The IR spectrum of Compound 2.
Notes
 Compound is benzaldehyde. The absorption in the 3100 cm–1 region shows sp2 C–H stretching, a resonance-weakened C=O stretch is seen at 1700 cm–1, and aromatic C=C stretching bands can be seen at 1600 and 1460 cm–1.
Keywords
 figure, 13.30, benzaldehyde, IR
13-31
Title
 Figure 13.31
Caption
 The IR spectrum of Compound 3.
Notes
 The compound is 2-propyn-1-ol. A broad O–H stretching band is seen around 3300 cm–1 superimposed on a sharp C–H stretching band characteristic of a terminal alkyne. Only sp3 C–H stretching is seen in the area near 3000 cm–1, and a triple bond causes the stretching producing the band at 2100 cm–1.
Keywords
 figure, 13.31, IR, 2-propyn-1-ol
13-32
Title
 Figure 13.32
Caption
 The IR spectrum of Compound 4.
Notes
 Compound 4 is N-methylacetamide. Stretching of a single N–H bond is seen at 3300 cm–1, sp3 C–H stretching is seen at 2950 cm–1, C=O stretching weakened by the presence of the amide nitrogen is seen at 1660 cm–1, and N–H bending causes the absorption at 1650 cm–1.
Keywords
 figure, 13.32, IR, N-methylacetamide
13-33
Title
 Figure 13.33
Caption
 The IR spectrum of Compound 5.
Notes
 Compound 5 is 1-phenyl-2-butanone. Both sp2 and sp3 C–H stretching can be seen in the region around 3000 cm–1, an unperturbed C=O stretch can be seen at 1720 cm–1, aromatic C–C stretching shows up at 1605 and 1500 cm–1, and one methyl bending vibration causes the sharp absorption at 1380 cm–1.
Keywords
 figure, 13.33, IR, 1-phenyl-2-butanone
13-34
Title
 Figure 13.34
Caption
 The IR spectrum for Problem 29.
Notes
 Figure 13.34 shows an IR spectrum of methyl vinyl ketone. Both sp2 and sp3 C–H stretching can be seen in the region around 3000 cm–1, and a C=O stretch of a carbonyl conjugated with a double bond causes the sharp absorption at 1680 cm–1.
Keywords
 figure, 13.34, IR, methyl, vinyl, ketone
13-35
Title
 Figure 13.35
Caption
 The IR spectrum for Problem 39a.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.35, problem, 39a
13-36
Title
 Figure 13.36
Caption
 The IR spectrum for Problem 39b.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.36, problem, 39b
13-37
Title
 Figure 13.37
Caption
 The IR spectrum for Problem 39c.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.37, problem, 39c
13-38
Title
 Figure 13.38
Caption
 The IR spectrum for Problem 45a.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.38, problem, 45a
13-39
Title
 Figure 13.39
Caption
 The IR spectrum for Problem 45b.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.39, problem, 45b
13-40
Title
 Figure 13.40
Caption
 The IR spectrum for Problem 45c.
Notes
 Pick the correct structure corresponding to the spectrum in the figure.
Keywords
 figure, 13.40, problem, 45c
13-41a-c
Title
 Figure 13.41
Caption
 The IR spectra for Problem 46.
Notes
 Each of the spectra is of one of the five possible compounds shown in the problem. Match the spectra with the choices.
Keywords
 IR, spectra, problem, 46
13-42
Title
 Figure 13.42
Caption
 The IR spectrum for Problem 48.
Notes
 The figure shows the IR spectrum of a compound with the formula C5H8O. Solve the structure.
Keywords
 Figure, 13.42, IR, problem, 48
13-43
Title
 Figure 13.43
Caption
 The IR spectrum for Problem 50.
Notes
 Problem 50 shows structures for five aromatic compounds. Choose the compound consistent with the IR spectrum in the figure.
Keywords
 figure, 13.43, problem, 50
13-44
Title
 Figure 13.44
Caption
 The IR spectrum for Problem 51.
Notes
 Problem 51 shows the structures of five aromatic compounds. Choose the compound whose structure is consistent with the IR spectrum in the figure.
Keywords
 figure, 13.44, problem, 51, IR
13-45
Title
 Figure 13.45
Caption
 The IR and mass spectra for Problem 54a.
Notes
 Determine the identity of the organic compound with molecular weight 100, whose structure is consistent with the IR and mass spectra shown.
Keywords
 figure 13.45, IR, problem, 54a
13-46
Title
 Figure 13.46
Caption
 The IR and mass spectra for Problem 54b.
Notes
 Determine the identity of the organic compound with molecular weight 162, whose structure is consistent with the IR and mass spectra shown.
Keywords
 figure 13.45, IR, problem, 54b
13-47
Title
 Figure 13.47
Caption
 The IR and mass spectra for Problem 54c.
Notes
 Determine the identity of the organic compound with molecular weight 72, whose structure is consistent with the IR and mass spectra shown.
Keywords
 figure 13.45, IR, problem, 54c
13-TB01
Title
 Table 13.1 Classes of Organic Compounds
Caption
Notes
Keywords

Title
 Table 13.2 The Natural Abundance of Isotopes Commonly Found in Organic Compounds
Caption
Notes
Keywords

Title
 Table 13.3 The Exact Masses of Some Common Isotopes
Caption
Notes
Keywords
13-TB05
Title
 Table 13.5 IR absorption of Carbon-Hydrogen Bonds
Caption
Notes
Keywords
13-14-01T04
Title
 Table 13.4 Important IR stretching frequencies
Caption
 Important IR stretching frequencies.
Notes
 Stretching frequencies and relative intensities of bands associated with stretching vibrations of various types of bonds.
Keywords
 table, 13.4, IR, stretching, frequencies
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