15. Analytical Techniques:IR, NMR, Mass Spect

What does cross peak X in Figure 14.34 tell you?

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In the context of $1^H$ NMR spectroscopy, into how many peaks will each proton shown in red be split if it has two equivalent neighboring protons?

Tell precisely how you would use the proton NMR spectra to distinguish between the following pairs of compounds.

(b)

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

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

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.

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When heated with chromic acid, compound A forms benzoic acid. Identify compound A from its ¹H NMR spectrum.

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

b. C₈H₉Br: a 3H doublet at 2.01 ppm a 1H quartet at 5.14 ppm

a 5H broad singlet at 7.35 ppm

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

n.

(b) Provide an arrow-pushing mechanism for the reaction.

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Sketch your predictions of the proton NMR spectra of the following compounds.

(a) CH₃–O–CH₂CH₃

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

b. C₆H₁₂O

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

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

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(b) Draw the proton NMR spectrum you would expect for butan-2-one. How well do the proton chemical shifts predict the carbon chemical shifts using the "15 to 20 times as large" rule of thumb?

Each of these four structures has molecular formula C₄H₈O₂. Match the structure with its characteristic proton NMR signals. (Not all of the signals are listed in each case.)

(a) sharp 1H singlet at δ8.0 and 2H triplet at δ4.0

(b) sharp 3H singlet at δ2.0 and 2H quartet at δ4.1

(c) sharp 3H singlet at δ3.7 and 2H quartet at δ2.3

(d) broad 1H singlet at δ11.5 and 2H triplet at δ2.3