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Chapter 14: Q23P (page 527)

Question: How many peaks are observed in the \({}^1H\) NMR signal for each proton shown in red in palau'amine, the complex chapter-opening molecule?

Short Answer

Expert verified

\({H_a}\): doublet

\({H_b}\): doublet

\({H_c}\): singlet

\({H_d}\): doublet

Step by step solution

01

The (n+1) rule

The (n +1) rule is used to predict the multiplicity of\({}^{\bf{1}}{\bf{H}}\)NMR peaks.

n represents the number of hydrogen atoms present on the carbon atoms adjacent to the carbon to which the desired hydrogen is connected.

02

Peaks observed in the \({}^{\bf{1}}{\bf{H}}\) NMR spectrum of palau'amine

The number of peaks observed for the indicated hydrogen atoms is as follows:

\({H_a}\): \(1\; + \;1\; = \;2\) (doublet).

\({H_b}\): \(1\; + \;1\; = \;2\) (doublet)

\({H_c}\): singlet (as it is connected to a nitrogen atom).

\({H_d}\): \(1\; + \;1\; = \;2\) (doublet)

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Most popular questions from this chapter

Question:Propose a structure consistent with each set of spectral data:

a. C4H8Br2: IR peak at 3000–2850cm-1 ;

NMR (ppm):

1.87 (singlet, 6 H)

3.86 (singlet, 2 H)

b. C3H6Br2: IR peak at 3000–2850cm-1 ;

NMR (ppm):

2.4 (quintet)

3.5 (triplet)

c. C5H10O2: IR peak at 1740cm-1 ;

NMR (ppm):

1.15 (triplet, 3 H) 2.30 (quartet, 2 H)

1.25 (triplet, 3 H) 4.72 (quartet, 2 H)

d . C6H14O: IR peak at 3600-3200 cm-1 ;

NMR (ppm):

0.8 (triplet, 6 H) 1.5 (quartet, 4 H)

1.0 (singlet, 3 H) 1.6 (singlet, 1 H)

e. C6H14O: IR peak at 3000-2850cm-1 ;

NMR (ppm):

1.10 (doublet, relative area = 6)

3.60 (septet, relative area = 1)

f . C3H6O: IR peak at 1730cm-1 ;

NMR (ppm):

1.11 (triplet)

2.46 (multiplet)

9.79 (triplet)

Identify the carbon atoms that give rise to the signals in the \)^{{\bf{13}}}{\bf{C}}\) NMR spectrum of each compound.

a. \){\bf{C}}{{\bf{H}}_{\bf{3}}}{\bf{C}}{{\bf{H}}_{\bf{2}}}{\bf{C}}{{\bf{H}}_{\bf{2}}}{\bf{C}}{{\bf{H}}_{\bf{2}}}{\bf{OH}}\); \)^{{\bf{13}}}{\bf{C}}\) NMR: 14, 19, 35, and 62 ppm

b. \){\left( {{\bf{C}}{{\bf{H}}_{\bf{3}}}} \right)_{\bf{2}}}{\bf{CHCHO}}\); \)^{{\bf{13}}}{\bf{C}}\) NMR: 16, 41, and 205 ppm

c. \){\bf{C}}{{\bf{H}}_{\bf{2}}}{\bf{ = CHCH}}\left( {{\bf{OH}}} \right){\bf{C}}{{\bf{H}}_{\bf{3}}}\); \)^{{\bf{13}}}{\bf{C}}\) NMR: 23, 69, 113, and 143 ppm

Question: What effect does increasing the operating frequency of a1HNMR spectrum have on each value: (a) the chemical shift inδ ;(b) the frequency of an absorption in Hz; (c) the magnitude of a coupling constant J in Hz?

Which of the highlighted carbon atoms in each molecule absorbs farther downfield?

a.

b.

c.

d.

How many signals are present in the 1HNMR spectrum for each molecule? What splitting is observed in each signal?

a.

b.

c.
See all solutions

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