NMR Practice

Problem: Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

9m

Problem: Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

7m

NMR Practice Additional Practice Problems

Draw the expected NMR spectrum of methyl propionate, and point out how it differs from the spectrum of ethyl acetate.

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The NMR spectrum of cinnamaldehyde follows.

(a) Determine the chemical shifts of Ha, Hb,and Hc. The absorption of one of these protons is difficult to see; look carefully at the integrals.

(b) Estimate the coupling constants Jab and Jbc

(c) Draw a tree to analyze the complex splitting of the proton centered at δ 6.7.

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Draw the NMR spectra you expect for the following compounds. 

Protons on the  carbon of an  -unsaturated carbonyl compound absorb at very low fields (about ) because of the electronwithdrawing resonance effect of the carbonyl group.

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Draw the NMR spectra you would expect for the following compounds.

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The NMR spectrum of toluene (methylbenzene) was shown in Figure 13-11. (a) How many different kinds of protons are there in toluene? (b) Explain why the aromatic region around  is broad, with more than one sharp absorption Figure 13-11

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

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Identify the following compounds. (Relative integrals 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 an area ratio of 2 : 3.

b. The 1H NMR spectrum of a compound with molecular formula C6H10O2 has two singlets with an area ratio of 2 : 3.

c. The 1H NMR spectrum of a compound with molecular formula C8H6O2 has two singlets with an area ratio of 1 : 2.

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

Reference: Problem 4:

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

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

a. C9H12

b. C5H10O


c. C9H10O2

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

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

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The 1H NMR spectrum shown in Figure 1 corresponds to one of the following compounds. Which compound is responsible for this spectrum?

Figure 1


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Draw an isomer of dichlorocyclopropane that gives an 1H NMR spectrum

a. with one signal.             b. with two signals.            c. with three signals.

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

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How could :H NMR spectra distinguish between the following compounds?

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Sketch what you believe the 1H NMR spectrum of compound X would look like:

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Sketch an approximation of the 1H NMR spectrum for the following molecule:

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The reaction between compound 1 and NaOCHMe2 in Me2CHOH as a solvent produces a mixture of two products 2 and 3, all with identical molecular formula and with a relative yield of 50% and 50% respectively. The 1NMR of these compounds with relative integrations of signals is shown below. What are the structures of compounds 2 and 3?

b. With what reagent and solvent would you treat compound 1 if you want to obtain higher yield of compound 2? Explain your answer with 1-2 sentences

c.  With what reagent and solvent would you treat compound 1 if you want to obtain higher yield of compound 3? Explain your answer with 1-2 sentences

d.  Based on the data above, what product(s) and in what relative ratio(s) would you obtain by treating compound 4 ((t-But)2CHCH(Br)CH3) with NaOCHMe2 in Me2CHOH as the solvent under the same conditions as above? Explain your answer with 1-2 sentences.

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Predict the 1H NMR of compound A in CDCl3. Show clearly the relative intensity, chemical shift and splitting pattern of each peak. Indicate in the spectrum, using the appropriate number shown for the carbons, where the protons resonate. Note: add as reference peaks the TMS and residual CHCl3.

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A compound C4H9Br gave the following 1HNMR spectrum: triplet, δ 1.0 (3H); doublet, δ 1.7; multiplet, δ 1.8; multiplet, δ 4.1 (1H) Which is a reasonable structure for the compound?

A) CHCH2CHBrCH3

B) CH3CH2CH2CH2Br

C) (CH3)2CHCH2Br

D) (CH3)3CBr

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A compound C5H10O gave the following spectral data:

1H NMR spectrum                              IR spectrum

doublet, δ 1.10                                  strong peak

singlet, δ 2.10                                   near 1720 cm    -1

septet, δ 2.50

Which is a reasonable structure for the compound?

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An unknown compound W has the molecular formula C 4H8O2. Based on the following 1H NMR spectrum, what is the structure of compound W? 
 

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The molecular formula, IR & NMR are provided for the following unknown compounds. For each problem, provide the structural information from the IR & NMR and propose a structure for the unknown.

 

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Which of the following atoms has a quantum spin number?

A) 2H

B) 12C

C) 15N

D) 16O

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Compound A can be converted into compound B by the reaction shown below. Considering the two 1H NMR spectra provided, draw the structures corresponding to compounds Aand B in the box.

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The 1H NMR spectrum of Compound C (C10H14O) is shown below. Draw the structure of the compound C in the box provided. Mark down your thought process. Even if the final structure is wrong, partial credit might be given if your analysis and approach make sense.

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The 1H NMR spectra for the following molecule is provided. In the fragments box below, propose which fragments are elucidated by the spectra and use arrows to match those fragments to each signal on the spectra, respectively. 

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Answer the following questions about product identity based on IR & NMR spectroscopy.

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Which structure is consistent with the following 1H NMR spectrum?

a ethyl acetate

b 2-propanone

c 3,3-dimethyl-2-pentanone

d ethyl 2,2-dimethylpropionate

e none of theses

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Which of the compound listed below has a structure consistent with the following   1H NMR spectrum?

a. 4-bromoanisole
b. Anisole
c. 4-bromoaniline
d. None of them
e. Phenol

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What  1H NMR spectral data is expected for the compound shown?

a. 3.8 (1H, septet), 2.1 (3H, s), 1.0 (6H, d)                        c 3.3 (3H, s), 2.6 (3H, septet), 1.0 (6H, d)

b. 3.8 (1H, septet), 9.3 (3H, s), 1.0 (6H, d)                        d 2.6 (1H, septet), 2.1 (3H, s), 1.0 (6H, d)

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In the boxes provided, place that letter (A, B, C, etc.) that corresponds to the signals in the spectrum provided below.

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Circle the molecule that corresponds to the NMR spectrum shown below.

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Circle the molecule that corresponds to the NMR spectrum shown below.

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There are four constitutional isomers of dichloropropane. The NMRs of 3 of these are shown below. Match each isomer with its NMR and provide an interpretation of each spectrum. (i.e. draw the structure on the NMR and  label protons , with their splitting.)

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Predict the structure of the compound that gives rise to the following  1H NMR spectra.

Molecular Formula C5H9CIO

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Sketch the 1H NMR spectrum and assign the peaks in each of the following compound.

 

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Which compound belongs to following 1H NMR?

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Which compound  shows  three signals (all singlets) in 1H NMR spectrum?

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Assign the 1H NMR to the appropriate structure out of the following possibilities. Choose the letter corresponding to the appropriate molecule  for this question. 

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Assign the 1H NMR to the appropriate structure out of the following possibilities. Choose the letter corresponding to the appropriate molecule  for this question. 

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Assign the 1H NMR to the appropriate structure out of the following possibilities. Choose the letter corresponding to the appropriate molecule  for this question. 

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Which structure is consistent with this  1H NMR spectrum?

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Which structure is consistent with this  1H NMR spectrum?

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Which structure is consistent with this  1H NMR spectrum?

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Which 1H NMR spectrum is consistent with that of ethyl methyl sulfide, CH 3CH2SCH3?

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The 1H NMR spectrum of a compound with formula C 7H14O gives two signals. Which of these structures is a possible one for this compound?

A) 2-Heptanone

B) 3-Heptanone

C) 2,4-Dimethyl-3-pentanone

D) 2,2-Dimethyl-3-pentanone

E) Two of the above

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Which of the following aromatic compounds most likely generated the accompanying 1H-NMR spectrum?

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How would you distinguish between these compounds via  1H NMR?

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Predict the structure of the compound that gives rise to the following  1H NMR spectra: Molecular Formula: C9H11Cl

 

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 Predict the structure of the compound that gives rise to the following  1H NMR spectra: Molecular Formula: C4H8O

 

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