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Compound F , a hydrocarbon with M + =96 in its mass spectrum, undergoes reaction with HBr to yield compound G . Propose structures for F and G , whose 13 C NMR spectral data are given below. Compound F Broadband-decoupled 13 C NMR: 27.6, 29.3, 32.2, 132.4 δ DEPT-90: 132.4 δ DEPT-135: positive peak at 132.4 δ; negative peaks at 27.6, 29.3, 32.2 δ Compound G Broadband-decoupled 13 C NMR: 25.1, 27.7, 39.9, 56.0 δ DEPT-90: 56.0 δ DEPT-135: positive peak at 56.0 δ; negative peaks at 25.1, 27.7, 39.9 δ

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Organic Chemistry

9th Edition
John E. McMurry
Publisher: Cengage Learning
ISBN: 9781305080485

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BuyFindarrow_forward

Organic Chemistry

9th Edition
John E. McMurry
Publisher: Cengage Learning
ISBN: 9781305080485
Chapter 13.SE, Problem 64GP
Textbook Problem
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Compound F, a hydrocarbon with M+=96 in its mass spectrum, undergoes reaction with HBr to yield compound G. Propose structures for F and G, whose 13C NMR spectral data are given below.

Compound F

Broadband-decoupled 13C NMR: 27.6, 29.3, 32.2, 132.4 δ DEPT-90: 132.4 δ

DEPT-135: positive peak at 132.4 δ; negative peaks at 27.6, 29.3, 32.2 δ

Compound G

Broadband-decoupled 13C NMR: 25.1, 27.7, 39.9, 56.0 δ DEPT-90: 56.0 δ

DEPT-135: positive peak at 56.0 δ; negative peaks at 25.1, 27.7, 39.9 δ

Interpretation Introduction

a)

Interpretation:

The molecular formula and the structure of an unknown compound to be predicted using spectrum details.

Concept introduction:

Molecular formula:

It represents the types of atoms with their total number present in a given molecule.

Mass spectroscopy:

It is a form of spectroscopic technique which is used for the elucidation of the molecular formula and molecular weight of the compound, depending upon the mass of the molecule.

Molecular ion peak (M)+.:

It is defined as the heaviest peak in the IR spectrum of the molecule which represents the largest molecular ion in the given molecule with greater m/z value.

The (M+1)+. peak:

It denotes the peak that arises next to molecular ion peak in the mass spectrum. The peak arises due to the presence of the isotope of carbon (13C).

(M+1)+. peak in mass spectroscopy is used to explain the number of carbon atoms present in a molecule depending on the abundance of (M+1)+. peak.

1HNMR: The 1HNMR spectrum gives information on the different electronic environment of protons. The number of signal (proton types) generated in 1HNMR are predicted by performing symmetry operations (rotation or reflection symmetry).

The 13CNMR spectrum gives information on the different electronic environments of carbon. As like 1HNMR, the number of signals generated in 13CNMR are predicted by performing symmetry operations (rotation or reflection symmetry). Only chemical shift values are reported in the spectrum but not the multiplicity and integration values because the coupling between two neighboring 13C-13 C nuclei are weakly involved due to the low abundance of 13C isotopes of carbon atom.

To Identify:

The structure to be predicted for C7H12

Broadband-decoupled 13CNMR spectrum:

The spectra provide information regarding the total number of carbon environments.

DEPT (Distortionless enhancement by polarization transfer):

(a) DEPT-90: The spectrum exhibits signal only from CH group and no signals from CH3, CH2, CH and quaternary carbon (carbon with no protons).

(b) DEPT-135: The spectrum exhibits CH3 groups and CH groups as positive signals (pointing up); CH2 groups appear as negative signals (pointing down) and quaternary carbon does not appear.

The signals appear in each type of spectrum:

Organic Chemistry, Chapter 13.SE, Problem 64GP , additional homework tip  1

Explanation of Solution

HDI Calculation:

Interpret the mass spectrum details.

a) The height of the parent ion (M+1)+. indicates that the compound has four carbons (1.1% for each carbon atom). Generally the half of the molecular weight is due to carbon atoms since the parent ion (M)+. appears at m/Z=96 hints the molecular weight of the carbons in the molecular formula would be (7X12=84). Thus the rest of the molecular formula weight must be attributed to oxygens and hydrogens...

Interpretation Introduction

b)

Interpretation:

The molecular formula and the structure of an unknown compound to be predicted using spectrum details.

Concept introduction:

Molecular formula:

It represents the types of atoms with their total number present in a given molecule.

Mass spectroscopy:

It is a form of spectroscopic technique which is used for the elucidation of the molecular formula and molecular weight of the compound, depending upon the mass of the molecule.

Molecular ion peak (M)+.:

It is defined as the heaviest peak in the IR spectrum of the molecule which represents the largest molecular ion in the given molecule with greater m/z value.

The (M+1)+. peak:

It denotes the peak that arises next to molecular ion peak in the mass spectrum. The peak arises due to the presence of the isotope of carbon (13C).

(M+1)+. peak in mass spectroscopy is used to explain the number of carbon atoms present in a molecule depending on the abundance of (M+1)+. peak.

1HNMR: The 1HNMR spectrum gives information on the different electronic environment of protons. The number of signal (proton types) generated in 1HNMR are predicted by performing symmetry operations (rotation or reflection symmetry).

The 13CNMR spectrum gives information on the different electronic environments of carbon. As like 1HNMR, the number of signals generated in 13CNMR are predicted by performing symmetry operations (rotation or reflection symmetry). Only chemical shift values are reported in the spectrum but not the multiplicity and integration values because the coupling between two neighboring 13C-13 C nuclei are weakly involved due to the low abundance of 13C isotopes of carbon atom.

Broadband-decoupled 13CNMR spectrum:

The spectra provide information regarding the total number of carbon environments.

DEPT (Distortionless enhancement by polarization transfer):

(a) DEPT-90: The spectrum exhibits signal only from CH group and no signals from CH3, CH2, CH and quaternary carbon (carbon with no protons).

(b) DEPT-135: The spectrum exhibits CH3 groups and CH groups as positive signals (pointing up); CH2 groups appear as negative signals (pointing down) and quaternary carbon does not appear.

The signals appear in each type of spectrum:

Organic Chemistry, Chapter 13.SE, Problem 64GP , additional homework tip  2

To Identify:

The structure to be predicted for C7H12

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Chapter 13 Solutions

Organic Chemistry
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