For each of the following compounds, identify the expected chemical shift for each type

For each of the following compounds, determine whether the two protons shown in red are homotopic, enantiotopic, or diastereotopic: (a) H H OMe H H (b) Cl H H OH (c) O (d) H H (e) H H

Butane (C4H10) exh bits only two different kinds of protons, shown here in red and blue. H3C C C CH3 H H H H (a) Explain why all four protons shown in red are chemically equivalent. (b) Explain why all six protons shown in blue are chemically equivalent. (c) How many different kinds of protons are present in pentane? (d) How many different kinds of protons are present in hexane? (e) How many different kinds of protons are present in 1-chlorohexane? 16.3 Identify the structure of a compound with molecular formula C5H12 that exhibits only one kind of proton. That is, all 12 protons are chemically equivalent.

Identify the structure of a compound with molecular formula C5H12 that exhibits only one kind of proton. That is, all 12 protons are chemically equivalent.

Identify the number of signals expected in the 1 H NMR spectrum of each of the following compounds: (a) OMe MeO (b) (c) (d) Me Cl (e) Cl Cl (f) Cl Br (g) (h) (i) Br Br (j) Br (k) O (l) O

We saw a general rule that the two protons of a CH2 group will be chemically equivalent if there are no chirality centers in the compound. An example of an exception is 3-bromopentane. This compound does not possess a chirality center. Nevertheless, the two highlighted protons are not chemically equivalent. Explain. Br H H

Identify the structure of a compound with molecular formula C9H20 that exhibits four CH2 groups, all of which are chemically equivalent. How many total signals would you expect in the 1 H NMR spectrum of this compound?

Predict the chemical shifts for the signals in the 1 H NMR spectrum of each of the following compounds: (a) O O (b) O O O O (c) O (d) O O (e)

A 1 H NMR spectrum was acquired for each of the following constitutional isomers. Comparison of the spectra reveals that only one of these spectra exhibits a signal between 6 and 7 ppm. Identify the structure that corresponds with this spectrum. O O O O O O O O O

A 1 H NMR spectrum was acquired for each of the following two compounds. One spectrum exhibits two signals downfield of 2.0 ppm, while the other spectrum exhibits only one signal downfield of 2.0 ppm. Match each spectrum with its corresponding compound. O O O

For each of the following compounds, identify the expected chemical shift for each type of proton: H O H (a) (b) OH (c) (d) O

A compound with molecular formula C5H10O2 has the following NMR spectrum. Determine the number of protons giving rise to each signal. 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 Proton NMR 33.2 Integration Values 48.4 33.3 48.7 0.5 ppm

A compound with molecular formula C10H10O has the following NMR spectrum. Determine the number of protons giving rise to each signal. 10 789 6 2345 Proton NMR Integration Values 18.7 17.1 87.1 51.1 1 ppm

A compound with molecular formula C4H6O2 has the following NMR spectrum. Determine the number of protons giving rise to each signal. 5.0 4.5 4.0 3.5 3.0 2.5 2.0 Proton NMR 18.92 Integration Values 19.77 19.46

The 1 H NMR spectrum of a compound with molecular formula C7H15Cl exhibits two signals with relative integration 2:3. Propose a structure for this compound.

For each of the following compounds, determine the multiplicity of each signal in the expected 1 H NMR spectrum: OO (d) O (c) O O (a) O (b

Propose the structure for a compound that lacks a methyl group but nevertheless exhibits a quartet in its 1 H NMR spectrum.

Below are NMR spectra of several compounds. Identify whether these compounds are likely to contain ethyl, isopropyl, and/or tert-butyl groups: (a) Chemical Shift (ppm) 8 7 6 1 6 5 5 4 3 2 1 0 Proton NMR C9H12 (b) 1.01.52.02.53.03.54.04.55.0 0.5 Proton NMR C6H12O2 2 1 6 3 Chemical Shift (ppm) (c) 8 7 6543 2 1 ppm Proton NMR C10H14O 11.9 12.1 6.0 Integration Values 55.0 (d) Chemical Shift (ppm) 8 7 6 5 4 3 2 5 2 1 1 Proton NM

Each of the three vinylic protons of styrene is split by the other two, and the J values are found to be Jab=11 Hz, Jac=17 Hz, and Jbc=1 Hz. Using this information, draw the expected splitting pattern for each of the three signals (Ha, Hb, and Hc). Ha Hb Hc Styrene

Draw the expected 1 H NMR spectrum for each of the following compounds: O O (a) H H O O O O O (b)

The 1 H NMR spectrum of a compound with molecular formula C7H14O3 exhibits only three signals, and all three signals appear downfield of 2 ppm on the spectrum. Propose a structure for this compound.

How would you use 1 H NMR spectroscopy to distinguish between the following compounds? O O (a) O O O (b) O O O (c) Cl HO Cl HO (d) (e) (f)

A chemist was attempting to achieve the following transformation: Br HBr Mass spectrometry was then used to verify that the molecular formula of the major product was C7H15Br, just as expected. However, the 1 H NMR spectrum of the product exhibited more than two signals. Identify what product was actually obtained. Can you suggest what might have caused formation of this product?

Propose a structure that is consistent with each of the following 1 H NMR spectra. In each case, the molecular formula is provided. (a) 8 7 6 5 4 3 2 1 ppm Proton NMR C8H10O 45.1 Integration Values 18.6 9 19.1 .1 (b) 3.5 3.0 2.5 2.0 1.5 1.0 ppm Proton NMR C7H14O Integration Values 10.8 65.7 (c) 8 7 6543 2 1 Proton NMR C10H14O 1 2 2 9 Chemical Shift (ppm) (d) 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 ppm Proton NMR triplet a triplet of triplets C4H6O2 18.02 Integration Values 19.77 19.46 (e) 456789 3 1 2 ppm Proton NMR C9H10O 13.9 Integration Values 21.5 14.2 20.9 (f) 3.0 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 ppm Proton NMR C5H12O Integration Values 13.6 27.8 84.5 41.9

A compound with molecular formula C10H10O4 produces a 1 H NMR spectrum that exhibits only two signals, both singlets. One signal appears at 3.9 ppm with a relative integration value of 79. The other signal appears at 8.1 ppm with a relative integration value of 52. Identify the structure of this compound.

For each of the following compounds, predict the number of signals and location of each signal in a 13C NMR spectrum: H O (a) (b) (c) (d) O (e) O (f) (g) (h) O (i) O O (j) O

Compare the following two constitutional isomers. The 13C NMR spectrum of the first compound exhibits five signals, while the second compound exhibits six signals. Explain. HO OH

Draw the structure of a compound with molecular formula C8H10 that exhibits five signals in its 13C NMR spectrum, four of which appear between 100 and 150 ppm.

Determine the structure of a compound with molecular formula C5H10O that exhibits the following broadband-decoupled and DEPT-135 spectra. The DEPT-90 spectrum has no signals. Chemical Shift (ppm) DEPT-135 220 200 180 160 140 120 100 80 60 40 20 0 220 200 180 160 140 120 100 80 60 40 20 0

Determine the structure of an alcohol with molecular formula C5H12O that exhibits the following signals in its 13C NMR spectra: (a) Broadband decoupled: 73.8 d, 29.1 d, and 9.5 d (b) DEPT-90: 73.8 d (c) DEPT-135: positive signals at 73.8 d and 9.5 d; negative signal at 29.1 d

A compound with molecular formula C7H14O exhibits the following 13C NMR spectra: Chemical Shift (ppm) DEPT-135 DEPT-90 220 200 180 160 140 120 100 80 60 40 20 0 220 200 180 160 140 120 100 80 60 40 20 0 220 200 180 160 140 120 100 80 60 40 20 0 Broadband-decoupled Several structures are consistent with these spectra. To determine which structure is correct, a 1 H NMR spectrum was acquired which exhibits five signals. One of those signals is a singlet at 1.9 ppm with an integration of 3, and another of the signals is a doublet at 0.9 ppm with an integration of 6. Using this information, identify the correct structure of the compound.

Each of the following compounds exhibits a 1 H NMR spectrum with only one signal. Deduce the structure of each compound: (a) C5H10 (b) C5H8Cl4 (c) C12H18

A compound with molecular formula C12H24 exhibits a 1 H NMR spectrum with only one signal and a 13C NMR spectrum with two signals. Deduce the structure of this compound.

A compound with molecular formula C17H36 exhibits a 1 H NMR spectrum with only one signal. How many signals would you expect in the 13C NMR spectrum of this compound?

How many signals would you expect in the 1 H NMR spectrum of each of the following compounds: (a) Cl Br (b) Cl (c) Br Br Cl (d) Cl (e) Cl (f)

How many signals would you expect in the 13C NMR spectrum of each of the compounds in Problem 16.34?

How would you distinguish between the following compounds using 13C NMR spectroscopy? OH OH

Predict the multiplicity of each signal in the 1 H NMR spectrum of the following compound: O

For each pair of compounds, identify how you would distinguish them using either 1 H NMR spectroscopy or 13C NMR spectroscopy: O O O O (a) F Cl Cl F (b) Cl Cl OH O (c) O O (d

A compound with molecular formula C8H18 exhibits a 1 H NMR spectrum with only one signal. How many signals would you expect in the 13C NMR spectrum of this compound?

For each of the following compounds, compare the two indicated protons and determine whether they are enantiotopic, homotopic, or diastereotopic: Cl Cl H Me Me H (a) Cl (b) H H H (c) H Cl Cl (f) H H H H (e) H H (d) H H Me (g) OH H H (h) F H F H (i) H H (j) O HO OH H H (k) HO OH H H (l) MeO H MeO H (m) Cl Cl (n) H H Cl Cl (o) HH

Draw the expected 1 H NMR spectrum of the following compound: O O

Consider the following compound: Br I F Cl (a) How many signals do you expect in the 1 H NMR spectrum of this compound? (b) Rank the protons in terms of increasing chemical shift. (c) How many signals do you expect in the 13C NMR spectrum? (d) Rank the carbon atoms in terms of increasing chemical shift.

A compound with molecular formula C9H18 exhibits a 1 H NMR spectrum with only one signal and a 13C NMR spectrum with two signals. Deduce the structure of this compound.

How many signals do you expect in the 1 H NMR spectrum of each of the following compounds: Geraniol Isolated from roses and used in perfumes OH (a) Dopamine A neurotransmitter that is deficient in Parkinsons disease HO HO NH2 (b) Isoprene (c) A precursor for natural rubber

Rank the signals of the following compound in terms of increasing chemical shift. Identify the proton(s) giving rise to each signal: H O O OH O C

Predict the expected number of signals in the 13C NMR spectrum of each of the following compounds. For each signal, identify where you expect it to appear in the 13C NMR spectrum: (a) O (b) O O O (c) O

When 1-methylcyclohexene is treated with HCl, a Markovnikov addition is observed. How would you use 1 H NMR spectroscopy to determine that the major product is indeed the Markovnikov product?

How many signals are expected in the 1 H NMR spectrum of each of the following compounds? (a) (b) (c) (d) (e) NO2 O O (f) (g) Cl (h)

Compare the structures of ethylene, acetylene, and benzene. Each of these compounds produces only one signal in its 1 H NMR spectrum. Arrange these signals in order of increasing chemical shift. H H H H H H

Assuming a 300-MHz instrument is used, calculate the difference between the frequency of absorption (in hertz) of TMS and the frequency of absorption of a proton with a d value of 1.2 ppm.

A compound with molecular formula C13H28 exhibits a 1 H NMR spectrum with two signals: a septet with an integration of 1 and a doublet with an integration of 6. Deduce the structure of this compound.

A compound with molecular formula C8H10 produces three signals in its 13C NMR spectrum and only two signals in its 1 H NMR spectrum. Deduce the structure of the compound.

A compound with molecular formula C3H8O produces a broad signal between 3200 and 3600 cm-1 in its IR spectrum and produces two signals in its 13C NMR spectrum. Deduce the structure of the compound.

A compound with molecular formula C4H6O4 produces a broad signal between 2500 and 3600 cm-1 in its IR spectrum and produces two signals in its 1 H NMR spectrum (a singlet at 12.1 ppm with a relative integration of 1 and a singlet at 2.4 ppm with a relative integration of 2). Deduce the structure of the compound.

Propose the structure of a compound that exhibits the following 1 H NMR data: (a) C5H10O 1.09 d (6H, doublet) 2.12 d (3H, singlet) 2.58 d (1H, septet) (b) C5H12O 0.91 d (3H, triplet) 1.19 d (6H, singlet) 1.50 d (2H, quartet) 2.24 d (1H, singlet) (c) C4H10O 0.90 d (6H, doublet) 1.76 d (1H, multiplet) 3.38 d (2H, doublet) 3.92 d (1H, singlet) (d) C4H8O2 1.21 d (6H, doublet) 2.59 d (1H, septet) 11.38 d (1H, singlet)

A compound with molecular formula C8H10O produces six signals in its 13C NMR spectrum and exhibits the following 1 H NMR spectrum. Deduce the structure of the compound. Chemical Shift (ppm) 8 7 6 5 4 2 2 2 3 1 3 2 1 0

Deduce the structure of a compound with molecular formula C9H12 that produces the following 1 H NMR spectrum: Chemical Shift (ppm) 8 7 6 1 6 5 5 4 3 2 1 0

Deduce the structure of a compound with molecular formula C9H10O2 that produces the following 1 H NMR spectrum and 13C NMR spectrum: 3URWRQ 105                &KHPLFDO 6KLIW SSP &DUERQ 105           &KHPLFDO 6KLIW SSP

Propose the structure of a compound consistent with the following data: (a) C5H10O, broadband-decoupled 13C NMR: 7.1, 34.6, 210.5 d (b) C6H10O, broadband-decoupled 13C NMR: 70.8, 116.2, 134.8 d

Determine the structure of an alcohol with molecular formula C4H10O that exhibits the following signals in its 13C NMR spectra: (a) Broadband decoupled: 69.3 d, 32.1 d, 22.8 d, and 10.0 d (b) DEPT-90: 69.3 d (c) DEPT-135: positive signals at 69.3 d, 22.8 d, and 10.0 d; negative signal at 32.1 d

Determine the structure of an alcohol with molecular formula C6H14O that exhibits the following DEPT-135 spectrum: 70 60 50 40 30 20 10 0 Chemical Shift (ppm) DEPT 135

Deduce the structure of a compound with molecular formula C6H14O2 that exhibits the following IR, 1 H NMR, and 13C NMR spectra: Proton NMR 1 3 2 2 2 2 2 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm) Wavenumber (cm1 ) 4000 3500 3000 2500 2000 1500 1000 % Transmittance 0 20 40 60 80 100 Carbon NMR 100 80 60 40 20 0 Chemical Shift (ppm)

Deduce the structure of a compound with molecular formula C8H10O that exhibits the following IR, 1 H NMR, and 13C NMR spectra: Wavenumber (cm1 ) 4000 3500 3000 2500 2000 1500 1000 % Transmittance 0 20 40 60 80 100 Proton NMR Carbon NMR 3 2 2 3 160 140 120 100 20406080 0 7 6 5 4 3 2 Chemical Shift (ppm)

Deduce the structure of a compound with molecular formula C5H10O that exhibits the following IR, 1 H NMR, and 13C NMR spectra. Data from the mass spectrum are also provided. Proton NMR Carbon NMR 3 2 2 2 1 140 120 100 80 60 40 20 0 6.0 5.5 5.0 4.5 4.0 3.5 1.41.6 1.01.2 Chemical Shift (ppm) Chemical Shift (ppm) Wavenumber (cm1)

Deduce the structure of a compound with molecular formula C8H14O3 that exhibits the following IR, 1 H NMR, and 13C NMR spectra: :DYHQXPEHU FP         7UDQVPLWWDQFH   Proton NMR 10 89 7 6 5 34 2 1 0 Chemical Shift (ppm) 2 00 1.50 Expansion TMS triplet triplet Carbon NMR DEPT-135 200 160 120 80 40 0 Chemical Shift (ppm) Proton decoupled 200 160 120 80 40 0

Deduce the structure of a compound with molecular formula C6H10O4 that exhibits the following IR, 1 H NMR, and 13C NMR spectra (Angew. Chem. Int. Ed. 2011, 50, 83878390): Wavenumber (cm1 ) 4000 3500 3000 2500 2000 1500 1000 % Transmittance 1747 Proton NMR 10 89 7 6 5 34 2 1 0 Chemical Shift (ppm) Expansion 5.5 4.5ppm 2.5 1 5 ppm 1 3 3 3 &DUERQ 105       &KHPLFDO 6KLIW SSP

Deduce the structure of a compound with molecular formula C8H14O4 that exhibits the following IR, 1 H NMR, and 13C NMR spectra: :DYHQXPEHU FP         7UDQVPLWWDQFH  quartet triplet 3URWRQ 105          &KHPLFDO 6KLIW SSP 706 Carbon NMR DEPT-135 200 160 120 80 40 0 Chemical Shift (ppm) Proton decoupled 200 160 120 80 40 0 Solvent

Deduce the structure of a compound with molecular formula C12H8Br2 that exhibits the following 1 H NMR and 13C NMR spectra: Proton NMR 10 89 7 6 5 34 2 1 0 Chemical Shift (ppm) 7.8 7.6 7.4 7.2 Expansion TMS &DUERQ 105       3URWRQ GHFRXSOHG 6ROYHQW &KHPLFDO 6KLIW SSP

An unknown compound exhibits the following IR, 1 H NMR, and 13C NMR spectra. In a mass spectrum of this compound, the (M)+ peak appears at m/z = 104, and the (M+1)+ peak is 4.4% the height of the parent ion. Elemental analysis reveals that the compound consists only of carbon, hydrogen and oxygen atoms. Wavenumber (cm1 ) 4000 3500 3000 2500 2000 1500 1000 % Transmittance 3420 1742 3URWRQ 105          &KHPLFDO 6KLIW SSP       SSP     ([SDQVLRQ 706 9DQLVKHV LQ ' 2 6ROYHQW &DUERQ 105 '(37        &KHPLFDO 6KLIW SSP 3URWRQ GHFRXSOHG       (a) Determine the molecular formula of the compound. (b) Deduce the structure of the compound.

Consider the structure of N,N-dimethylformamide (DMF): H N O CH3 CH3 We might expect the two methyl groups to be equivalent; however, both the proton and carbon NMR spectra of DMF show two separate signals for the methyl groups. Propose an explanation for the nonequivalence of the methyl groups. Would you expect the signals to collapse into one signal at high temperature? (Hint: You may want to turn to Section 2.12 and consider the hybridization state of the nitrogen atom.)

Consider the two methyl groups shown in the following compound. Explain why the methyl group on the right side appears at lower chemical shift. 1.0 ppm H3C CH3 0.8 ppm

Brevianamide S, a potent antitubercular natural product, was recently isolated from a marine sediment collected off the coast of China (Org. Lett. 2012, 14, 47704773). Predict the chemical shift and determine the multiplicity of each signal in the 1 H NMR spectrum for brevianamide S (chemical shifts have been provided in situations where the relevant benchmark values were not covered in this chapter). N N O O N NH N O O NH H H H H 4.1 ppm 7.4 ppm 7.7 ppm Brevianamide S

The hydronaphthacene ring system consists of five fused sixmembered rings, as shown below in compounds 3 and 4. One method for construction of this ring system involves treatment of compound 1 with a Fischer carbene such as 2. Two diastereomeric products are obtained, 3 and 4, differing only in the configuration at one chirality center (Tetrahedron Lett. 2011, 52, 41824185). Explain how you could distinguish these two products using only 13C NMR. CHO SiMe3 SiMe3 OMe Cr(CO)5 ( )2 Me3Si Me3Si OH H H 1 2 3 - (R) 4 - (S) O O

Treatment of 1,3,6-cyclononatriene (compound 1), or its dimethyl derivative (compound 2), with potassium amide (KNH2) in liquid ammonia results in the formation of anion 1a or 2a, respectively (J. Am. Chem. Soc. 1973, 95, 34373438): 1 2 3 4 5 6 7 8 9 R R Compound 1 (R=H) Compound 2 (R=CH3) KNH2 1a (anion) KNH2 2a (anion) (a) Draw all four resonance structures of 1a. (b) How many signals do you expect in the 1 H NMR spectrum of 1a and of 2a? (c) The 1 H NMR spectrum of 1a exhibits signals at 3.74 and 3.39 ppm, representing the protons at positions C1 and C3, respectively, while the protons at positions C2 and C4 produce signals at 5.63 and 5.52 ppm, respectively. Explain the two discrete groups of signals. (d) In the 1 H NMR spectrum of 2a, how many signals do you expect to appear in the range 34 ppm, and how many signals in the range 56 ppm?

Compound 1 can serve as a precursor in the synthesis of flutamide (2), a drug used in the treatment of prostate cancer (J. Chem. Ed. 2003, 80, 14391443): O2N CF3 NH2 O2N CF3 N H O Cl O Pyridine 1 2 (Flutamide) Ha Hc Hb Ha Hb Hc (a) Compound 1 has three distinct aromatic protons, labeled Ha, Hb, and Hc. Identify which aromatic proton gives rise to the signal most downfield. Justify your choice with an analysis of resonance effects and inductive effects. (b) Consider the same three aromatic protons in compound 2. Do you expect these three signals to be shifted upfield or downfield relative to the same three signals for compound 1? Explain your reasoning and predict which of the protons are most affected by the transformation of 1 to 2.

Coumarin (1) and its derivatives exhibit a broad array of industrial applications, including, but not limited to, cosmetics, food preservatives, and fluorescent laser dyes. In the 1 H NMR spectrum of compound 2 (a coumarin derivative), the two signals farthest downfield are at 7.38 and 8.42 ppm (J. Chem. Ed. 2006, 83, 287289): 1 O O O O N O 2 3 4 (a) Identify the two protons that most likely give rise to these signals and justify your decision using resonance structures. (b) Do you expect the IR signal corresponding to the C3!C4 p bond to be a stronger signal in compound 1 or in compound 2? Explain your reasoning.