Chapter 13.SE, Problem 55GP

Propose structures for compounds that fit the following ¹H NMR data:

(a) C₄H₆Cl₂

2.18 δ (3 H, singlet)

4.16 δ (2 H, doublet, J=7 Hz)

5.71 δ (1 H, triplet, J=7 Hz)

(b) C₁₀H₁₄

1.30 δ (9 H, singlet)

7.30 δ (5 H, singlet)

(c) C₄H₇BrO

2.11 δ (3 H, singlet)

3.52 δ (2 H, triplet, J=6 Hz)

4.40 δ (2 H, triplet, J=6 Hz)

(d) C₉H₁₁Br

2.15 δ (2 H, quintet, J=7 Hz)

2.75 δ (2 H, triplet, J=7 Hz)

3.38 δ (2 H, triplet, J=7 Hz)

7.22 δ (5 H, singlet)

Interpretation Introduction

a)

Interpretation:

The proposed structure of the compound to be identified for the given ¹HNMR spectrum.

Concept introduction:

HDI calculation:

Where

C represent number of carbons.

N represent number of nitrogens.

H represent number of hydrogens.

X represent number of halogens.

Chemical shift: The frequency of the proton signal in the spectrum with reference to the standard compound which may be TMS(Tetramethylsilane) shows signal at 0 ppm(parts per million).

Multiplicity: The number of peaks on the each signal in NMR spectrum is defined as multiplicity; the multiplicity of each signal indicates the neighboring protons. It is generated by coupling of the subjected protons with the neighboring protons (both subjected and neighbor protons are to be chemically not equivalent) separated by either two or three sigma bonds.

Rule: Multiplicity of each signal is calculated using (n+1) rule only when the neighboring protons are chemically equivalent to each other.

(n+1)

where

n indicates number of neighboring protons

Integration value (I): The integration value at the bottom of the ¹HNMR spectrum represents the number of protons giving rise to the signal.

To find:

The structure of the compound to be identified for the given molecular formula and ¹HNMR spectrum.

Answer to Problem 55GP

Explanation of Solution

Calculate HDI value:

The HDI calculation confirms the presence of an aliphatic ring and double bond

Adjust the relative integration with the number of protons from the molecular formula.

The total number of protons in the molecular formula C10H14 is 6.

Interpret the given information.

Given information:

Three signals with multiplicity and integration values.

2.18ppm(3H, singlet)

4.16ppm(2H, doublet, J=7HZ)

5.71ppm(¹H , triplet, J=7HZ)

The HDI value confirms the compound has either a ring or a double bond (one level of unsaturation). The total integration value (3+2+1=6 protons) is also an exact value with the protons of the molecular formula.

A signal at 2.18ppm with integration of 3H’s represents methyl groups which are chemically equivalent having one neighboring proton indicates the characteristic pattern of isopropyl group.

A signal with integration of 2H’s represent a methylene group appears at 4.16ppm rather 5.17ppm, consistent with the value of protons which present at alpha position to vinyl group (C=O) and accounts for the one degree of unsaturation.

The overall predicted structure is:

The methyl groups can be interchanged via no reflectional symmetry and the compound gives rise to totally three signals in spectrum.

Conclusion

The structure of the compound is identified using the details of spectrum and DHI calculation.

Interpretation Introduction

b)

Interpretation:

The proposed structure of the compound to be identified for the given ¹HNMR spectrum.

Concept introduction:

HDI calculation:

Where

C represent number of carbons.

N represent number of nitrogens.

H represent number of hydrogens.

X represent number of halogens.

Chemical shift: The frequency of the proton signal in the spectrum with reference to the standard compound which may be TMS(Tetramethylsilane) shows signal at 0 ppm(parts per million).

Multiplicity: The number of peaks on the each signal in NMR spectrum is defined as multiplicity; the multiplicity of each signal indicates the neighboring protons. It is generated by coupling of the subjected protons with the neighboring protons (both subjected and neighbor protons are to be chemically not equivalent) separated by either two or three sigma bonds.

Rule: Multiplicity of each signal is calculated using (n+1) rule only when the neighboring protons are chemically equivalent to each other.

(n+1)

where

n indicates number of neighboring protons

Integration value (I): The integration value at the bottom of the ¹HNMR spectrum represents the number of protons giving rise to the signal.

To find:

The structure of the compound to be identified for the given molecular formula and ¹HNMR spectrum.

Answer to Problem 55GP

Explanation of Solution

Calculate HDI value:

The HDI calculation confirms the presence of an aliphatic ring and double bond

Adjust the relative integration with the number of protons from the molecular formula.

The total number of protons in the molecular formula C₁₀H₁₄ is 14.

Interpret the given information.

Given information:

Three signals with multiplicity and integration values.

1.30ppm(9H, singlet)

7.30ppm(5H, singlet)

The HDI value confirms the compound has either a ring or a double bond (four level of unsaturation). The total integration value (9+5=14 protons) is also an exact value with the protons of the molecular formula.

A signal at 1.30ppm with integration of 9H’s represents methyl groups which are chemically equivalent having one neighboring proton indicates the characteristic pattern of isopropyl group.

A signal with integration of 5H’s represent a benzene appears at 7.30ppm which present at aromatic group and accounts for the four degree of unsaturation.

The overall predicted structure is:

The methyl groups can be interchanged via reflectional symmetry and the compound gives rise to totally two signals in ¹HNMR spectrum.

Conclusion

The structure of the compound is identified using the details of ¹HNMR spectrum and DHI calculation.

Interpretation Introduction

c)

Interpretation:

The proposed structure of the compound to be identified for the given ¹HNMR spectrum.

Concept introduction:

HDI calculation:

Where

C represent number of carbons.

N represent number of nitrogens.

H represent number of hydrogens.

X represent number of halogens.

Chemical shift: The frequency of the proton signal in the spectrum with reference to the standard compound which may be TMS(Tetramethylsilane) shows signal at 0 ppm(parts per million).

Multiplicity: The number of peaks on the each signal in NMR spectrum is defined as multiplicity; the multiplicity of each signal indicates the neighboring protons. It is generated by coupling of the subjected protons with the neighboring protons (both subjected and neighbor protons are to be chemically not equivalent) separated by either two or three sigma bonds.

Rule: Multiplicity of each signal is calculated using (n+1) rule only when the neighboring protons are chemically equivalent to each other.

(n+1)

where

n indicates number of neighboring protons

Integration value (I): The integration value at the bottom of the spectrum represents the number of protons giving rise to the signal.

To find:

The structure of the compound to be identified for the given molecular formula and ¹HNMR spectrum.

Answer to Problem 55GP

Explanation of Solution

Calculate HDI value:

The HDI calculation confirms the presence of an aliphatic ring and double bond

Adjust the relative integration with the number of protons from the molecular formula.

The total number of protons in the molecular formula C₄H₇Bro is 7.

Interpret the given information.

Given information:

Three signals with multiplicity and integration values.

2.11ppm(3H, singlet)

3.52ppm(2H, triplet, J=6HZ)

4.40ppm(2H, triplet, J=6HZ)

The HDI value confirms the compound has either a ring or a double bond (one level of unsaturation). The total integration value (3+2+2=7 protons) is also an exact value with the protons of the molecular formula.

A signal at 2.11ppm with integration of 3H’s represents methyl groups which are chemically equivalent having one neighboring proton indicates the characteristic pattern of isopropyl group.

A two signal with integration of 2H’s represent a methylene group appears at 3.52ppm rather 4.40ppm, consistent with the value of protons which present at alpha position to carbonyl group(C=O) and accounts for the one degree of unsaturation.

The overall predicted structure is:

The methyl groups can be interchanged via no reflectional symmetry and the compound gives rise to totally three signals in spectrum.

Conclusion

The structure of the compound is identified using the details of ¹HNMR spectrum and DHI calculation.

Interpretation Introduction

d)

Interpretation:

The proposed structure of the compound to be identified for the given ¹HNMR spectrum.

Concept introduction:

HDI calculation:

Where

C represent number of carbons.

N represent number of nitrogens.

H represent number of hydrogens.

X represent number of halogens.

Chemical shift: The frequency of the proton signal in the spectrum with reference to the standard compound which may be TMS(Tetramethylsilane) shows signal at 0 ppm(parts per million).

Multiplicity: The number of peaks on the each signal in NMR spectrum is defined as multiplicity; the multiplicity of each signal indicates the neighboring protons. It is generated by coupling of the subjected protons with the neighboring protons (both subjected and neighbor protons are to be chemically not equivalent) separated by either two or three sigma bonds.

Rule: Multiplicity of each signal is calculated using (n+1) rule only when the neighboring protons are chemically equivalent to each other.

(n+1)

where

n indicates number of neighboring protons

Integration value (I): The integration value at the bottom of the spectrum represents the number of protons giving rise to the signal.

To find:

The structure of the compound to be identified for the given molecular formula and ¹HNMR spectrum.

Answer to Problem 55GP

Explanation of Solution

Calculate HDI value:

The HDI calculation confirms the presence of an aliphatic ring and double bond

Adjust the relative integration with the number of protons from the molecular formula.

The total number of protons in the molecular formula C₉H₁₁Br is 11.

Interpret the given information.

Given information:

Three signals with multiplicity and integration values.

2.15ppm(2H, quintet, J=7HZ)

2.75ppm(2H, triplet, J=7HZ)

3.38ppm(2H, triplet, J=7HZ)

7.22ppm(5H, singlet)

The HDI value confirms the compound has either a ring or a double bond (four level of unsaturation). The total integration value (2+2+2+5=11 protons) is also an exact value with the protons of the molecular formula.

A signal at 2.15ppm with integration of 2H’s represents three methyl groups which are chemically equivalent having one neighboring proton indicates the characteristic pattern of alkyl group.

A signal with integration of 2H’s represent benzylic appears at 2.75ppm which present at aromatic group

A signal with integration of 5H’s represent benzylic appears at 7.30ppm which present at aromatic group and accounts for the four degree of unsaturation.

The overall predicted structure is:

The methyl groups can be interchanged via reflectional symmetry and the compound gives rise to totally four signals in spectrum.

Conclusion

The structure of the compound is identified using the details of ¹HNMR spectrum and DHI calculation.