Chapter 10.5, Problem 17E

(a)

Interpretation Introduction

Interpretation:Absorbance corresponding to carbon-carbon double bond and the vinylic hydrogen atoms in the IR and NMR spectra of $\text{1-hexene}$ should be specified.

Concept introduction: Infrared absorption frequencies values are given as follows:

  

The scale used for the NMR spectrum is delta scale. $\text{δ}$ denotes parts per million units. The lower values of $\text{δ}$ denote upfield while higher values of $\text{δ}$ denote downfield region. Each peak in the NMR spectrum corresponds to distinct hydrogen.

The area within each peak corresponds to the number of equivalent protons found at that chemical shift values.

Spin-spin splitting is observed as a result of the interaction amongst non-equivalent NMR active nuclei. This is independent of the strength of the external magnetic field. The formula to calculate the number of peaks in the ${}^1\text{H}$ NMR spectra is as follows:

  $\text{Number of peaks}=N+1$

Where,

• $N$ is the number of equivalent protons on the adjacent carbon atoms.

Thus if a fragment is $-{\text{CH}}_{\text{2}}-{\text{CH}}_{\text{3}}-$ then it would show a three proton triplet due to ${\text{CH}}_{\text{3}}$ and a two proton quartet in accordance with $N+1$ the rule.

The typical chemical shifts values are given as follows:

  

Explanation of Solution

IR spectrum of $\text{1-hexene}$ is as follows:

  

Three signals at frequencies ${\text{985 cm}}^{-1}$ , $1650{\text{ cm}}^{-1}$ and ${\text{3000 cm}}^{-1}$ correspond to vinylic bending, $\text{C}=\text{C}$ and $\text{C}=\text{C}-\text{H}$ absorption signals respectively.

(b)

Interpretation Introduction

Interpretation: The various resonances corresponding to ${}^1\text{H}$ NMR of hydrogen nuclei found in $\text{1-hexene}$ should be assigned.

Concept introduction:The scale used for the NMR spectrum is delta scale. $\text{δ}$ denotes parts per million units. The lower values of $\text{δ}$ denote upfield while higher values of $\text{δ}$ denote downfield region. Each peak in the NMR spectrum corresponds to distinct hydrogen.

The area within each peak corresponds to the number of equivalent protons found at that chemical shift values.

Spin-spin splitting is observed as a result of the interaction amongst non-equivalent NMR active nuclei. This is independent of the strength of the external magnetic field. The formula to calculate the number of peaks in the ${}^1\text{H}$ NMR spectra is as follows:

  $\text{Number of peaks}=N+1$

Where,

• $N$ is the number of equivalent protons on the adjacent carbon atoms.

Thus if a fragment is $-{\text{CH}}_{\text{2}}-{\text{CH}}_{\text{3}}-$ then it would show a three proton triplet due to ${\text{CH}}_{\text{3}}$ and a two proton quartet in accordance with $N+1$ the rule.

Explanation of Solution

The typical chemical shifts values are given as follows:

  

The NMR spectrum of $\text{1-hexene}$ is given as follows:

  

Signals for olefinic hydrogen and two proton doublet for terminal olefinic protons at $\delta \text{ 5}\text{.82}$ , 5.03 and 4.97 are evident from the spectrum.

The slight downfield signal of the methylene proton signal attached immediately next to olefin appears at 2.18.For each methylene protons set that is farther the $\text{δ}$ value is close to 1.

Therefore various resonances corresponding to ${}^1\text{H}$ NMR of hydrogen nuclei found in $\text{1-hexene}$

are assigned as follows:

  

(c)

Interpretation Introduction

Interpretation: The various resonances corresponding to ${}^{13}\text{C}$ NMRofcarbon nuclei found in $\text{1-hexene}$ should be assigned.

Concept introduction: The scale used for the NMR spectrum is the delta scale. $\text{δ}$ denotes parts per million units. The lower values of $\text{δ}$ denote upfield while higher values of $\text{δ}$ denoting downfield region. Each peak in the NMR spectrum corresponds to distinct hydrogens.

Thus if a fragment is $-{\text{CH}}_{\text{2}}-{\text{CH}}_{\text{3}}-$ then it would show two carbon signals for each of theses carbon.

Explanation of Solution

The typical chemical shifts values are given as follows:

  

  ${}^{13}\text{C}$ NMR data is given as follows:

  $\delta \text{ 14}\text{.0, 22}\text{.5, 31}\text{.6, 33}\text{.8, 114}\text{.3, 139}\text{.2}$

A total of 6 distinct signal peaks are given this indicates that there are six types of non-equivalent carbon in $\text{1-hexene}$ .

The signal near to 114.3 is for terminal olefinic carbon and near 139.2 is for other olefinic carbon. For the rest of the ${\text{sp}}^{\text{3}}$ hybridized carbons signals appear near diminished $\delta$

values assigned as follows: