back

Chapter 13
Mass Spectrometry and Infrared Spectroscopy

Lecture Resource (.ppt)

PowerPoint Image Gallery (.ppt)

 

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

© 1995-2002 by Prentice-Hall, Inc.
A Pearson Company
Distance Learning at Prentice Hall
Legal Notice