Chapter 31, Problem 31.1P

One component of jojoba oil is a wax formed from eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ and ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$. Draw the structure of the wax, including the cis geometry of both carbon–carbon double bonds.

Interpretation Introduction

Interpretation: The structure of the wax formed from eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ and ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$, including the cis geometry of both carbon-carbon double bonds is to be stated.

Concept introduction: Waxes are lipids, which are hydrolysable. They contain ester $\left({\text{RCOOR}}^{\text{'}}\right)$ as the functional group, and obtained from alcohol $\left({\text{R}}^{\text{'}}\text{OH}\right)$ and a fatty acids $\left(\text{RCOOH}\right)$ of high molecular weight.

Answer to Problem 31.1P

The structure of the wax formed from eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ and ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$, including the cis geometry of both carbon-carbon double bonds is shown below.

Figure 1

Explanation of Solution

Waxes are lipids, which are hydrolysable. They contain ester $\left({\text{RCOOR}}^{\text{'}}\right)$ as the functional group, and obtained from alcohol $\left({\text{R}}^{\text{'}}\text{OH}\right)$ and a fatty acids $\left(\text{RCOOH}\right)$ of high molecular weight.

The treatment of eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ with ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$ is an esterification reaction. The reaction yields ester (desired wax) as the product and ${\text{H}}_{\text{2}}\text{O}$ as the by-product.

The structure of the wax formed from eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ and ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$, including the cis geometry of both carbon-carbon double bonds is shown below.

Figure 1

Conclusion

The structure of the wax formed from eicosenoic acid $\left[{\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{9}}{\text{CO}}_{\text{2}}\text{H}\right]$ and ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{8}}\text{OH}$, including the cis geometry of both carbon-carbon double bonds is shown on Figure 1.