In light of the nitrogen rule mentioned in 12-17, what is

Assume that you have two unlabeled samples, one of methylcyclohexane and the other of ethylcyclopentane. How could you use mass spectrometry to tell them apart? The mass spectra of both are shown in FIGURE 12-7. FIGURE 12-7 Mass spectra of unlabeled samples A and B for Worked Example 12-1.

The male sex hormone testosterone contains only C, H, and O and has a mass of 288.2089 amu, as determined by high-resolution mass spectrometry. What is the likely molecular formula of testosterone?

Two mass spectra are shown in FIGURE 12-8. One spectrum is that of 2-methyl2-pentene; the other is of 2-hexene. Which is which? Explain.

The mass spectrum of 2-methyl-3-pentanol is shown in FIGURE 12-14. What fragments can you identify? Equation Transcription: Text Transcription: CH_3CHCHCH_2CH_3 CH_3

What are the masses of the charged fragments produced in the following cleavage pathways? (a) Alpha cleavage of 2-pentanone \(\mathrm{(CH_3COCH_2CH_2CH_3)}\) (b) Dehydration of cyclohexanol (hydroxycyclohexane) (c) McLafferty rearrangement of 4-methyl-2-pentanone \(\mathrm{[CH_3COCH_2CH(CH_3)_2]}\) (d) Alpha cleavage of triethylamine \(\mathrm{[(CH_3CH_2)_3N]}\) Equation Transcription: Text Transcription: (CH_3COCH_2CH_2CH_3) [CH_3COCH_2CH(CH_3)_2] [(CH_3CH_2)_3N]

List the masses of the parent ion and of several fragments you might expect to find in the mass spectrum of the following molecule:

Which is higher in energy, FM radio waves with a frequency of \(1.015 \times 10^8\) Hz (101.5 MHz) or visible green light with a frequency of \(5 \times 10^{14}\) Hz? Equation Transcription: Text Transcription: 1.015 x 10^8 5 x 10^{14}

Which has higher energy, infrared radiation with \(\lambda=1.0 \times 10^{-6}\) m or an X ray with \(\lambda=3.0 \times 10^{-9}\) m? Radiation with \(v=4.0 \times 10^9\) Hz or with \(\lambda=9.0 \times 10^{-6}\) m? Equation Transcription: Text Transcription: lambda=1.0 x 10^{-6} lambda=3.0 x 10^{-9} v=4.0 x 10^9 lambda=9.0 x 10^{-6}

It’s useful to develop a feeling for the amounts of energy that correspond to different parts of the electromagnetic spectrum. Calculate the energies in kJ/mol of each of the following kinds of radiation: (a) A gamma ray with \(\lambda=5.0 \times 10^{-11}\) m (b) An X ray with \(\lambda=3.0 \times 10^{-9}\) m (c) Ultraviolet light with \(\nu=6.0 \times 10^{15}\) Hz (d) Visible light with \(\nu=7.0 \times 10^{14}\) Hz (e) Infrared radiation with \(\lambda=2.0 \times 10^{-5}\) m (f) Microwave radiation with \(\nu=1.0 \times 10^{11}\) Hz Equation Transcription: Text Transcription: lambda=5.0 x 10^{-11} lambda=3.0 x 10^{-9} v=6.0 x 10^{15} v=7.0 x 10^{14} lambda=2.0 x 10^{-5} v=1.0 x 10^{11}

Acetone \(\mathrm{(CH_3COCH_3)}\) and 2-propen-1-ol \(\mathrm{(H_2C=CHCH_2OH)}\) are isomers. How could you distinguish them by IR spectroscopy? Equation Transcription: Text Transcription: (CH_3COCH_3) (H_2C=CHCH_2OH)

What functional groups might the following molecules contain? (a) A compound with a strong absorption at \(\mathrm{1710\ cm^{-1}}\) (b) A compound with a strong absorption at \(\mathrm{1540~ cm^{-1}}\) (c) A compound with strong absorptions at \(\mathrm{1720\ cm^{-1}}\) and \(2500\) to \(\mathrm{3100\ cm^{-1}}\) Equation Transcription: Text Transcription: 1710 cm^-1 1540 cm^-1 1720 cm^-1 3100 cm^-1

How might you use IR spectroscopy to distinguish between the following pairs of isomers? (a) \(\mathrm{CH_3CH_2OH}\) and \(\mathrm{CH_3OCH_3}\) (b) Cyclohexane and 1-hexene (c) \(\mathrm{CH_3CH_2CO_2H}\) and \(\mathrm{HOCH_2CH_2CH_2CHO}\) Equation Transcription: Text Transcription: CH_3CH_2OH CH_3OCH_3 CH_3CH_2CO_2H HOCH_2CH_2CH_2CHO

Where might the following compounds have IR absorptions? Equation Transcription: Text Transcription: CH_2OH CH_3 HCCCH_2CHCH_2COCH_3

The IR spectrum of an unknown compound is shown in FIGURE 12-27. What functional groups does the compound contain? Equation Transcription: Text Transcription: Wavenumber (cm^-1)

Where might the following compounds have IR absorptions? Equation Transcription: Text Transcription: COCH_3 HCCCH_2CH_2CH CO_2H CH_2OH

Where might the following compound have IR absorptions?

Where in the IR spectrum would you expect each of the following molecules to absorb?

Show the structures of the fragments you would expect in the mass spectra of the following molecules:

Propose structures for compounds that it the following mass-spectral data: (a) A hydrocarbon with \(\mathrm{M^+=132}\) (b) A hydrocarbon with \(\mathrm{M^+=166}\) (c) A hydrocarbon with \(\mathrm{M^+=84}\) Equation Transcription: Text Transcription: M^+=132 M^+=166 M^+=84

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 atomic masses are: 1.007 83 \(\mathrm{(^1H)}\), 12.000 00 \(\mathrm{(^{12}C)}\), 14.003 07 \(\mathrm{(^{14}N)}\), 15.994 91 \(\mathrm{(^{16}O)}\). (a) \(\mathrm{M^+=98.0844}\) (b) \(\mathrm{M^+=123.0320}\) ________________ Equation Transcription: Text Transcription: (^1H) (^{12}C) (^{14}N) (^{16}O) M^+=98.0844 M^+=123.0320

Camphor, a saturated monoketone from the Asian camphor tree, is used among other things as a moth repellent and as a constituent of embalming fluid. If camphor has \(\mathrm{M^+=152.1201}\) by high-resolution mass spectrometry, what is its molecular formula? How many rings does camphor have? Equation Transcription: Text Transcription: M^+=152.1201

The \(nitrogen~ rule\) of mass spectrometry says that a compound containing an odd number of nitrogens has an odd-numbered molecular ion. Conversely, a compound containing an even number of nitrogens has an even-numbered \(\mathrm M^+\) peak. Explain. Equation Transcription: Text Transcription: M^+

In light of the nitrogen rule mentioned in Problem 12-17, what is the molecular formula of pyridine, \(\mathrm{M^+=79}\)? Equation Transcription: Text Transcription: M^+=79

Nicotine is a diamino compound isolated from dried tobacco leaves. Nicotine has two rings and \(\mathrm{M^+=162.1157}\) by high-resolution mass spectrometry. Give a molecular formula for nicotine, and calculate the number of double bonds. Equation Transcription: Text Transcription: M^+=162.1157

The hormone cortisone contains C, H, and O, and shows a molecular ion at \(\mathrm{M^+=360.1937}\) by high-resolution mass spectrometry. What is the molecular formula of cortisone? (The degree of unsaturation for cortisone is 8.) Equation Transcription: Text Transcription: M^+=360.1937

Halogenated compounds are particularly easy to identify by their mass spectra because both chlorine and bromine occur naturally as mixtures of two abundant isotopes. Recall that chlorine occurs as \(\mathrm{^{35}Cl}\) (75.8%) and \(\mathrm{^{37}Cl}\) (24.2%); and bromine occurs as \(\mathrm{^{79}Br}\) (50.7%) and \(\mathrm{^{81}Br}\) (49.3%). At what masses do the molecular ions occur for the following formulas? What are the relative percentages of each molecular ion? (a) Bromomethane, \(\mathrm{CH_3Br}\) (b) 1-Chlorohexane, \(\mathrm{C_6H_{13}Cl}\) ________________ Equation Transcription: Text Transcription: ^{35}Cl ^{37}Cl ^{79}Br ^{81}Br CH_3Br C_6H_{13}Cl

By knowing the natural abundances of minor isotopes, it’s possible to calculate the relative heights of \(\mathrm{M^+}\) and \(\mathrm{M+1}\) peaks. If \(\mathrm{^{13}C}\) has a natural abundance of 1.10%, what are the relative heights of the \(\mathrm{M^+}\) and \(\mathrm{M+1}\) peaks in the mass spectrum of benzene, \(\mathrm{C_6H_6}\)? Equation Transcription: Text Transcription: M^+ M+1 ^{13}C M^+ C_6H_6

Propose structures for compounds that it the following data: (a) A ketone with \(\mathrm{M^+=86}\) and fragments at m/z = 71 and m/z = 43 (b) An alcohol with \(\mathrm{M^+=88}\) and fragments at m/z = 73, m/z 5 70, and m/z = 59 Equation Transcription: Text Transcription: M^+=86 M^+=88

2-Methylpentane \(\mathrm{(C_6H_{14})}\) has the mass spectrum shown. Which peak represents \(\mathrm{M^+}\)? Which is the base peak? Propose structures for fragment ions of m/z = 71, 57, 43, and 29. Why does the base peak have the mass it does? Equation Transcription: Text Transcription: (C_6H_{14}) M^+

Assume that you are in a laboratory carrying out the catalytic hydrogenation of cyclohexene to cyclohexane. How could you use a mass spectrometer to determine when the reaction is finished?

What fragments might you expect in the mass spectra of the following compounds? Equation Transcription: Text Transcription: CH_3

How might you use IR spectroscopy to distinguish among the three isomers 1-butyne, 1,3-butadiene, and 2-butyne?

Would you expect two enantiomers such as (R)-2-bromobutane and (S)-2-bromobutane to have identical or different IR spectra? Explain.

Would you expect two diastereomers such as meso-2,3-dibromobutane and (2R,3R)-dibromobutane to have identical or different IR spectra? Explain.

Propose structures for compounds that meet the following descriptions: (a) \(\mathrm{C_5H_8}\), with IR absorptions at \(\mathrm{3300}\) and \(\mathrm{2150\ cm^{-1}}\) (b) \(\mathrm{C_4H_8O}\), with a strong IR absorption at \(\mathrm{3400~ cm^{-1}}\) (c) \(\mathrm{C_4H_8O}\), with a strong IR absorption at \(\mathrm{1715~cm^{-1}}\) (d) \(\mathrm{C_8H_{10}}\), with IR absorptions at \(\mathrm{1600}\) and \(\mathrm{1500~cm^{-1}}\) ________________ Equation Transcription: Text Transcription: C_5H_8 2150 cm^{-1} C_4H_8O 3400 cm^{-1} C_4H_8O 1715 cm^{-1} C_8H_{10} 1500 cm^{-1}

How could you use infrared spectroscopy to distinguish between the following pairs of isomers? (a) \(\mathrm {HC \equiv CCH_2NH_2}\) and \(\mathrm {CH_3CH_2C \equiv N}\) (b) \(\mathrm {CH_3COCH_3}\) and \(\mathrm {CH_3CH_2CHO}\) Equation Transcription: Text Transcription: HC equiv CCH_2NH_2 CH_3CH_2C equiv N CH_3COCH_3 CH_3CH_2CHO

Two infrared spectra are shown. One is the spectrum of cyclohexane, and the other is the spectrum of cyclohexene. Identify them, and explain your answer. Equation Transcription: Text Transcription: Wavenumber (cm^-1) Wavenumber (cm^-1)

At what approximate positions might the following compounds show IR absorptions? Equation Transcription: Text Transcription: CO_2H CO_2CH_3 C equiv N CH_3CCH_2CH_2COCH_3

How would you use infrared spectroscopy to distinguish between the following pairs of constitutional isomers? ________________ Equation Transcription: Text Transcription: CH_3C equiv CCH_3 CH_3CH_2C equiv CH CH_3CH=CHCH_3 CH_3CCH_2CH=CH_2 H_2C=CHOCH_3 CH_3CH_2CHO

At what approximate positions might the following compounds show IR absorptions? ________________ Equation Transcription: Text Transcription: CH_3CH_2CCH_3 CH_3 CH_3CHCH2C equiv CH CH_3 CH_3CHCH_2CH=CH_2 CH_3CH_2CH_2COCH_3 CH_3

Assume that you are carrying out the dehydration of 1-methylcyclohexanol to yield 1-methylcyclohexene. How could you use infrared spectroscopy to determine when the reaction is complete?

Assume that you are carrying out the base-induced dehydrobromination of 3-bromo-3-methylpentane (Section 11-7) to yield an alkene. How could you use IR spectroscopy to tell which of three possible elimination products is formed, if one includes E/Z isomers?

Which is stronger, the \(\mathrm {C=O}\) bond in an ester \(\mathrm {(1735~ cm^{-1})}\) or the \(\mathrm {C=O}\) bond in a saturated ketone \(\mathrm {(1715~ cm^{-1})}\)? Explain. Equation Transcription: Text Transcription: C=O (1735 cm^{-1}) C=O (1715 cm^{-1})

Carvone is an unsaturated ketone responsible for the odor of spearmint. If carvone has \(\mathrm {M^+=150}\) in its mass spectrum and contains three double bonds and one ring, what is its molecular formula? Equation Transcription: Text Transcription: M^+=150

Carvone (Problem 12-39) has an intense infrared absorption at \(\mathrm {1690~ cm^{-1}}\). What kind of ketone does carvone contain? Equation Transcription: Text Transcription: 1690 cm^{-1}

The mass spectrum (a) and the infrared spectrum (b) of an unknown hydrocarbon are shown. Propose as many structures as you can. Equation Transcription: Text Transcription: Wavenumber (cm^-1)

The mass spectrum (a) and the infrared spectrum (b) of another unknown hydrocarbon are shown. Propose as many structures as you can. Equation Transcription: Text Transcription: Wavenumber (cm^{-1})

Propose structures for compounds that meet the following descriptions: (a) An optically active compound \(\mathrm {C_5H_{10}O}\) with an IR absorption at \(\mathrm {1730~ cm^{-1}}\) (b) A non-optically active compound \(\mathrm {C_5H_9N}\) with an IR absorption at \(\mathrm {2215~ cm^{-1}}\) Equation Transcription: Text Transcription: C_5H_{10}O 1730 cm^{-1} C_5H_9N 2215 cm^{-1}

4-Methyl-2-pentanone and 3-methylpentanal are isomers. Explain how you could tell them apart, both by mass spectrometry and by infrared spectroscopy.

Grignard reagents undergo a general and very useful reaction with ketones. Methylmagnesium bromide, for example, reacts with cyclohexanone to yield a product with the formula \(\mathrm {C_7H_{14}O}\). What is the structure of this product if it has an IR absorption at \(\mathrm {3400~cm^{-1}}\)? Equation Transcription: Text Transcription: C_7H_{14}O 3400 cm^{-1} CH_3MgBr H_3O^+

Ketones undergo a reduction when treated with sodium borohydride, \(\mathrm {NaBH_4}\). What is the structure of the compound produced by reaction of 2-butanone with \(\mathrm {NaBH_4}\) if it has an IR absorption at \(\mathrm {3400~ cm^{-1}}\) and \(\mathrm {M^+=74}\) in the mass spectrum? ________________ Equation Transcription: Text Transcription: NaBH_4 NaBH_4 3400 cm^{-1} M^+=74 CH_3CH_2CCH_3 NaBH_4 H_3O^+

Nitriles, \(\mathrm {R-C \equiv N}\), undergo a hydrolysis reaction when heated with aqueous acid. What is the structure of the compound produced by hydrolysis of propane nitrile, \(\mathrm {CH_3CH_2C \equiv N}\), if it has IR absorptions from \(\mathrm {2500-3100~ cm^{-1}}\) and at \(\mathrm {1710~ cm^{-1}}\), and has \(\mathrm {M^+=74}\)? Equation Transcription: Text Transcription: R-C equiv N CH_3CH_2C equiv N 2500-3100 cm^{-1} 1710 cm^{-1} M^+=74

The infrared spectrum of the compound with the mass spectrum shown below lacks any significant absorption above \(\mathrm {3000~ cm^{-1}}\). There is a prominent peak near \(\mathrm {1740~ cm^{-1}}\) and another strong peak near \(\mathrm {1200~ cm^{-1}}\). Propose a structure consistent with the data. Equation Transcription: Text Transcription: 3000 cm^{-1} 1740 cm^{-1} 1200 cm^{-1}

The infrared spectrum of the compound with the mass spectrum shown below has a medium-intensity peak at about \(\mathrm {1650~ cm^{-1}}\). There is also a \(\mathrm {C-H}\) out-of-plane bending peak near \(\mathrm {880~ cm^{-1}}\). Propose a structure consistent with the data. Equation Transcription: Text Transcription: 1650 cm^-1 C-H 880 cm^-1

The infrared spectrum of the compound with the mass spectrum shown below has strong absorbances at \(\mathrm {1584, 1478,~ and~ 1446~ cm^{-1}}\). Propose a structure consistent with the data. Equation Transcription: Text Transcription: 1584, 1478, and 1446 cm^{-1}