The spectrum shown here is for a molecule with a molecular formula of C₄H₉Cl. Suggest a structure for this molecule.

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Draw the peak that would correspond to the hydrogens at C₃ in the molecule shown. Be sure to indicate the integration and place it at an appropriate chemical shift.

Calculate the index of hydrogen deficiency for curacin A, which has a molecular formula of C₂₃H₃₅NOS .

How many sets of equivalent hydrogens are in each molecule shown?

(a)

How many sets of equivalent hydrogens are in each molecule shown?

(b)

How many sets of equivalent hydrogens are in each molecule shown?

(c)

How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?

(a)

How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?

(b)

How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?

(c)

How many sets of equivalent hydrogens are present in the molecule that resulted in this NMR spectrum? [Recall that some signals can be split into multiple peaks—they are still just one signal.]

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If rotation is restricted, as in the case of the molecule shown, the hydrogens labeled a and b are nonequivalent. Why?

Without worrying about the relative location of the signals (i.e., the chemical shift) or the splitting patterns, draw a spectrum of the following molecule. Be sure to label each signal based on the set of equivalent hydrogens to which it corresponds.

For the molecules shown, give the number of signals expected and the relative ratio of the signal integrations.

(b)

Without worrying about the relative location of the signals (i.e., the chemical shift) or the splitting patterns, draw a spectrum of the following molecule, being sure to indicate the integration of each peak. Label each signal based on the set of equivalent hydrogens to which it corresponds. [We expand on this question in future assessments.]

(a) Calculate the resonance frequency of an aldehydic proton ( δ 9.3 ppm) if it is detected on a 60-MHz NMR spectrometer.

(b) What if it were detected on a 300-MHz instrument?

The methyl hydrogens in propane appear at a chemical shift of 0.9 ppm, whereas the methyl hydrogens of propene appear around 2.5 ppm. Explain.

An unknown compound (C₇H₆O) gives the IR spectrum shown here. At what chemical shifts would you expect to see signals in the ¹H NMR spectrum?

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In Figure 15.34, H_a was assumed to be 'up.' How does the analysis change if we assume instead that H_a is down?

Though Figure 15.34 was concerned with the appearance of H_a, how would H_b appear in the spectrum?

Draw all of the possible spin states to explain why a hydrogen with four neighbors appears as a quintet (quint, five peaks).

Being able to recognize patterns of integration and multiplicity for common functional groups makes structure identification more efficient. Draw the pattern of integration and multiplicity you'd expect to see for each common alkyl group.

(c)

Being able to recognize patterns of integration and multiplicity for common functional groups makes structure identification more efficient. Draw the pattern of integration and multiplicity you'd expect to see for each common alkyl group.

(d)

Draw a spectrum for each of the following molecules, being sure to indicate the multiplicity, integration, and chemical shift of each peak. Label each signal based on the set of equivalent hydrogens to which it corresponds.

(b)

Draw a spectrum for each of the following molecules, being sure to indicate the multiplicity, integration, and chemical shift of each peak. Label each signal based on the set of equivalent hydrogens to which it corresponds.

(c)

A chemist made what was thought to be compound A or B. How could coupling constants between H_a and H_b be used to distinguish between the two isomers? [Hint: Draw a chair conformation of each.]

What coupling constant would you expect between Hₐ and H₆ in cyclopent-2-en-1-one?

Alkene hydrogens usually appear at similar chemical shifts between 5 and 6 ppm. The alkene hydrogens in the structure shown are very different. Rationalize the difference in chemical shifts between Hₐ and H₆ in the structure shown.

Draw the expected signal for a hydrogen with the following coupling constants.

(a) Hₐ : δ 5.34 (Jₐ꜀ = 12 , Jₐ₆ = 2)

Draw the expected signal for a hydrogen with the following coupling constants.

(b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )

Though it wasn't discussed, what coupling constant would you expect for Hₐ and H꜀ in the spectrum of trans-but-2-enoic acid in Figure 15.50? Justify your answer.

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