Propose structures that are consistent with the following spectra. (Integral ratios are

What frequency (in MHz) is required to cause a proton to flip its spin when it is exposed to a magnetic field of 1 T?

a. Calculate the magnetic field (in tesla) required to flip an 1H nucleus in an NMR spectrometer that operates at 360 MHz. b. What strength magnetic field is required when a 500-MHz instrument is used for 1H NMR?

How many signals would you expect to see in the 1H NMR spectrum of each of the five compounds with molecular formula C6H14?

How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?

How could you distinguish the 1H NMR spectra of the following compounds?

Draw an isomer of dichlorocyclopropane that gives an 1H NMR spectrum a. with one signal. b. with two signals. c. with three signals.

How many hertz from the TMS signal is the signal occurring at 2.0 ppm a. in a 300 MHz spectrometer? b. in a 500 MHz spectrometer?

A signal is seen at 600 Hz from the TMS signal in an NMR spectrometer with a 300-MHz operating frequency. a. What is the chemical shift of the signal? b. What is its chemical shift in an instrument operating at 500 MHz? c. How many hertz from the TMS signal is the signal in a 500-MHz spectrometer?

a. If two signals differ by 1.5 ppm in a 300 MHz spectrometer, by how much do they differ in a 500 MHz spectrometer? b. If two signals differ by 90 Hz in a 300 MHz spectrometer, by how much do they differ in a 500 MHz spectrometer?

Where would you expect to find the 1H NMR signal of (CH3)2Mg relative to the TMS signal? (Hint: Magnesium is less electronegative than silicon.)

a. Which proton or set of protons in each of the following compounds is the least shielded? b. Which proton or set of protons in each compound is the most shielded? 1. CH3CH2CH2Cl Br Br 2. 3. CH3CHCHBr O C CH3CH2 OCH3 Br Br

Which underlined proton (or sets of protons) has the greater chemical shift (that is, the higher frequency signal)? a. Br Br CH3CHCHBr c. CH3CH2CHCH3 Cl e. CH3CH2CH CH2 b. CH3 CH3CHOCH3 d. O C CH3 CH3CH CH2CH3 f. CH3OCH2CH2CH3

Which underlined proton (or sets of protons) has the greater chemical shift (that is, the higher frequency signal)? a. CH3CH2CH2Cl or CH3CH2CH2Br b. CH3CH2CH2Cl or CH3CH2CHCH3 Cl c. O O CH3CH2 C or H C CH3CH2 OCH3

Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on. a. O CH3CH2 C H b. CH3CH2CHCH3 OCH3 c. ClCH2CH2CH2Cl d. CH3CH2CHCH2CH3 OCH3 f. CH3CH2CH2OCHCH3 CH3 h. CH3CHCH2OCH3 CH3 e. O OCH3 C CH3CH2CH2 g. O CH3 C CH3CH2CH2 i. CH3CHCHCH3 Cl

[18]-Annulene shows two signals in its 1H NMR spectrum: one at 9.25 ppm and the other to the right of the TMS signal at -2.88 ppm. What hydrogens are responsible for each of the signals? (Hint: Look at the direction of the induced magnetic field outside and inside the benzene ring in Figure 14.6.)

How would integration distinguish the 1H NMR spectra of the following compounds?

a. Calculate the ratios of the different kinds of protons in a compound with an integral ratio of 6 : 4 : 18.4 (going from left to right across the spectrum). b. Determine the structure of a compound with molecular formula C7H14O2 that gives these relative integrals in the observed order.a. Divide each number in the ratio by the smallest number: 6 4 = 1.5 4 4 = 1 18.4 4 = 4.6 Multiply the resulting numbers by a number that will make them close to whole numbers: 1.5 * 2 = 3 1 * 2 = 2 4.6 * 2 = 9 The ratio 3 : 2 : 9 gives the relative numbers of the different kinds of protons. Because the sum of the relative number of protons (14) is the same as the actual number of protons in the compound, we know that the actual ratio is the relative ratio and not some multiple of the relative ratio. b. The 3 suggests a methyl group, the 2 a methylene group, and the 9 a tert-butyl group. The methyl group is closest to the group in the molecule that causes deshielding, and the tert-butyl group is farthest away from the group that causes deshielding. The following compound meets these

Which of the following compounds is responsible for the 1H NMR spectrum shown below?

One of the spectra below is produced by 1-chloropropane and the other by 1-iodopropane. Which is which?

Explain how the following compounds, each with the same molecular formula, could be distinguished by their 1H NMR spectra.

The 1H NMR spectra of two carboxylic acids with molecular formula C3H5O2Cl are shown below. Identify the carboxylic acids. (The offset notation means that the farthest-left signal has been moved to the right by the indicated amount to fit on the spectrum; thus, the signal at 9.8 ppm offset by 2.4 ppm has an actual chemical shift of 9.8 + 2.4 = 12.2 ppm.)

Draw a diagram like the one shown in Figure 14.12 to predict a. the relative intensities of the peaks in a triplet. b. the relative intensities of the peaks in a quintet.

Indicate the number of signals and the multiplicity of each signal in the 1H NMR spectrum of each of the following compounds: a. CH3CH2CH2CH2CH2CH3 b. ICH2CH2CH2Br c. ClCH2CH2CH2Cl d. ICH2CH2CHBr2

Explain the relative chemical shifts of the benzene ring protons in Figure 14.18.

How can their 1H NMR spectra distinguish the following compounds?

Identify each compound from its molecular formula and its 1H NMR spectrum: a. C9H12

Predict the splitting patterns for the signals given by compounds in Problem 4.

Describe the 1H NMR spectrum you would expect for each of the following compounds, indicating the relative positions of the signals

Propose structures that are consistent with the following spectra. (Integral ratios are given from left to right across the spectrum.) a. The 1H NMR spectrum of a compound with molecular formula C4H10O2 has two singlets with integral ratios of 2 : 3. b. The 1H NMR spectrum of a compound with molecular formula C6H10O2 has two singlets with integral ratios of 2 : 3. c. The 1H NMR spectrum of a compound with molecular formula C8H6O2 has two singlets with integral ratios of 1 : 2.

Why is there no coupling between the a and c protons or between the b and c protons in the cis and trans alkenes shown in Figure 14.20?

Identify the compound with molecular formula C8H10O that gives the IR and 1H NMR spectra shown here.

Draw a splitting diagram for Hb, where a. Jba = 12 Hz and Jbc = 6 Hz. b. Jba = 12 Hz and Jbc = 12 Hz.

a. For the following compounds, which pairs of hydrogens (Ha and Hb) are enantiotopic hydrogens? b. Which pairs are diastereotopic hydrogens?

How many signals would you expect to see for the indicated hydrogens in the following compounds 1H NMR spectrum?

How would the 1H NMR spectra for the four compounds with molecular formula C3H6Br2 differ?

We expect the signal for the methyl protons adjacent to the diastereotopic hydrogens of 2-bromobutane to be a doublet of doublets as a result of splitting by the nonequivalent diastereotopic hydrogens. The signal, however, is a triplet. Use a splitting diagram to explain why it is a triplet rather than a doublet of doublets.

Explain why the chemical shift of the OH proton of a carboxylic acid is at a higher frequency than the chemical shift of an OH proton of an alcohol.

Which has a greater chemical shift for the OH proton, the 1H NMR spectrum of pure ethanol or the 1H NMR spectrum of ethanol dissolved in CH2Cl2?

Propose a mechanism for proton exchange of an alcohol in aqueous base.

Identify the compound with molecular formula C3H7NO responsible for the 1H NMR spectrum shown here.

Answer the following questions for each compound: a. How many signals are in its 13C NMR spectrum? b. Which signal is at the lowest frequency?

Describe the proton-coupled 13C NMR spectra for compounds 1, 3, and 5 in Problem 41, indicating the relative positions of the signals.

How can 1,2-, 1,3-, and 1,4-dinitrobenzene be distinguished by a. 1H NMR spectroscopy? b. 13C NMR spectroscopy?

Identify each compound below from its molecular formula and its 13C NMR spectrum.

Identify pairs of coupled protons in the compound whose COSY spectrum is shown below.

What does cross peak X in Figure 14.34 tell you?

How many signals are produced by each of the following compounds in its

Draw a splitting diagram for the Hb proton and give its multiplicity if

and so on. Indicate the multiplicity of each signal.

Determine the ratios of the chemically nonequivalent protons in a compound if the steps of the integration curves measure 40.5, 27, 13, and 118 mm, from left to right across the spectrum. Draw the structure of a compound whose 1H NMR spectrum would show these integrals in the observed order.

How can 1H NMR distinguish between the compounds in each of the following pairs?

Answer the following questions: a. What is the relationship between chemical shift in ppm and operating frequency? b. What is the relationship between chemical shift in hertz and operating frequency? c. What is the relationship between coupling constant in hertz and operating frequency? d. How does the operating frequency in NMR spectroscopy compare with the operating frequency in IR and UV/Vis spectroscopy?

Match each of the 1H NMR spectra with one of the following compounds:

The 1H NMR spectra of three isomers with molecular formula C4H9Br are shown here. Which isomer produces which spectrum?

Identify each of the following compounds from the 1H NMR data and molecular formula: a. C4H8Br2: a 6H singlet at 1.97 ppm a 2H singlet at 3.89 ppm b. C8H9Br: a 3H doublet at 2.01 ppm a 1H quartet at 5.14 ppm a 5H broad singlet at 7.35 ppm c. C5H10O2: a 3H triplet at 1.15 ppm a 3H triplet at 1.25 ppm a 2H quartet at 2.33 ppm a 2H quartet at 4.13 ppm

Identify the compound with molecular formula C7H14O that gives the following proton-coupled 13C NMR spectrum:

Compound A, with molecular formula C4H9Cl, shows two signals in its 13C NMR spectrum. Compound B, an isomer of compound A, shows four signals, and in the proton-coupled mode, the signal farthest downfield is a doublet. Identify compounds A and B.

Would it be better to use 1H NMR or 13C NMR spectroscopy to distinguish 1-butene, cis-2-butene, and 2-methylpropene? Explain your answer.

There are four esters with molecular formula C4H8O2. How can they be distinguished by 1H NMR?

Identify the compound with molecular formula C6H14 that is responsible for the following 1H NMR spectrum:

An alkyl halide reacts with an alkoxide ion to form a compound whose 1H NMR spectrum is shown here. Identify the alkyl halide and the alkoxide ion. (Hint: See Section 9.15.)

The 1H NMR spectra of three isomers with molecular formula C7H14O are shown here. Which isomer produces which spectrum?

Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra: Wavenumber (cm1)

Identify each of the following compounds from its molecular formula and its 13C NMR spectrum:

The 1H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum

How can the signals in the 6.5 to 8.1 ppm region of their 1H NMR spectra distinguish the following compounds?

The 1H NMR spectra of two compounds, each with molecular formula C11H16, are shown here. Identify the compounds.

Draw a splitting diagram for the Hb proton if Jbc = 10 and Jba = 5.

Sketch the following spectra that would be obtained for 2-chloroethanol: a. The 1H NMR spectrum for an anhydrous sample of the alcohol. b. The 1H NMR spectrum for a sample of the alcohol that contains a trace amount of acid. c. The 13C NMR spectrum. d. The proton-coupled 13C NMR spectrum. e. The four parts of a DEPT 13C NMR spectrum

How can 1H NMR be used to prove that the addition of HBr to propene follows the rule that says that the electrophile adds to the sp2 carbon bonded to the most hydrogens?

Identify each of the following compounds from its molecular formula and its 1H NMR spectrum:

Dr. N. M. Arr was called in to help analyze the 1H NMR spectrum of a mixture of compounds known to contain only C, H, and Br. The mixture showed two singletsone at 1.8 ppm and the other at 2.7 ppmwith relative integrals of 1 : 6, respectively. Dr. Arr determined that the spectrum was that of a mixture of bromomethane and 2-bromo-2-methylpropane. What was the ratio of bromomethane to 2-bromo-2-methylpropane in the mixture?

Calculate the amount of energy (in calories) required to flip an 1H nucleus in an NMR spectrometer that operates at 300 MHz.

The following 1H NMR spectra are for four compounds, each with molecular formula of C6H12O2. Identify the compounds.

When compound A (C5H12O) is treated with HBr, it forms compound B (C5H11Br). The 1H NMR spectrum of compound A has a 1H singlet, a 3H doublet, a 6H doublet, and two 1H multiplets. The 1H NMR spectrum of compound B has a 6H singlet, a 3H triplet, and a 2H quartet. Identify compounds A and B.

Identify the compound with molecular formula C6H10O that gives the following DEPT 13C NMR spectrum:

Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra: 3 2 1 a. C6H12O

How many signals are produced by each of the following compounds in its a. 1H NMR spectrum? b. 13C NMR spectrum?

Identify each of the following compounds from its mass spectrum, IR spectrum, and 1H NMR spectrum: