Chapter 18, Problem 18.9E

Interpretation Introduction

(a)

Interpretation:

Whether the fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{14}}\text{COOH}$ is saturated or unsaturated is to be indicated and whether it is solid or a liquid is to be stated.

Concept introduction:

A fatty acid having a long aliphatic chain with no double bond is called saturated fatty acid and a fatty acid that contains at least one double bond within the fatty acid chain is called unsaturated fatty acid. Due to the presence of a long alkyl side chain in saturated fatty acids, their packing efficiency is more than those of unsaturated fatty acids. As a result, unsaturated fatty acids possess lower melting point than saturated fatty acids. Thus, most of the saturated fatty acids are solid at room temperature.

Answer to Problem 18.9E

The fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{14}}\text{COOH}$ is a saturated fatty acid and it is solid at room temperature.

Explanation of Solution

The structural formula of fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{14}}\text{COOH}$ is given below.

Figure 1

The general name of the above fatty acid is palmitic acid. Palmitic acid has a long aliphatic chain of ${\text{-C}}_{\text{15}}{\text{H}}_{\text{31}}$ that follows the general formula of alkyl group $\left({\text{C}}_{\text{n}}{\text{H}}_{\text{2n+1}}\right)$. This shows that there is no double bond within the fatty acid chain. Therefore, the above fatty acid is a saturated fatty acid. Saturated fatty acid possesses a solid form due to favorable van der Waal’s interactions between side chains of adjacent molecule. Therefore, the saturated fatty acid is solid at room temperature.

Conclusion

The fatty acid shown in Figure 1 is a saturated fatty acid and it is solid at room temperature.

Interpretation Introduction

(b)

Interpretation:

Whether the fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{4}}\text{CH}={\text{CHCH}}_{\text{2}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{COOH}$ is saturated or unsaturated is to be indicated and whether it is a solid or a liquid is to be stated.

Concept introduction:

A fatty acid having a long aliphatic chain with no double bond is called saturated fatty acid and a fatty acid that contains at least one double bond within the fatty acid chain is called unsaturated fatty acid. Due to the presence of a long alkyl side chain in saturated fatty acids, their packing efficiency is more than those of unsaturated fatty acids. As a result, unsaturated fatty acids possess lower melting point than saturated fatty acids. Thus, most of the saturated fatty acids are solid at room temperature.

Answer to Problem 18.9E

The fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{4}}\text{CH}={\text{CHCH}}_{\text{2}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{COOH}$ is an unsaturated fatty acid and it is a liquid at room temperature.

Explanation of Solution

The structural formula of fatty acid ${\text{CH}}_{\text{3}}{\left({\text{CH}}_{\text{2}}\right)}_{\text{4}}\text{CH}={\text{CHCH}}_{\text{2}}\text{CH}=\text{CH}{\left({\text{CH}}_{\text{2}}\right)}_{\text{7}}\text{COOH}$ is given below.

Figure 2

The general name of the above fatty acid is lenoleic acid. The structural formula of lenoleic acid shows that there are two double bonds in the carbon chain. Therefore, lenoleic acid is an unsaturated fatty acid. The side chain in unsaturated fatty acids possess less van der Waal’s interactions between side chains of adjacent molecule. Therefore, the unsaturated fatty acid is a liquid at room temperature.

Conclusion

The fatty acid shown in Figure 2 is an unsaturated fatty acid and it is a liquid at room temperature.

Interpretation Introduction

(c)

Interpretation:

Whether the fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{\text{14}}{\text{H}}_{\text{24}}\right)\text{COOH}$ is saturated or unsaturated is to be indicated and whether it is a solid or a liquid is to be stated.

Concept introduction:

A fatty acid having a long aliphatic chain with no double bond is called saturated fatty acid and a fatty acid that contains at least one double bond within the fatty acid chain is called unsaturated fatty acid. Due to the presence of a long alkyl side chain in saturated fatty acids, their packing efficiency is more than those of unsaturated fatty acids. As a result, unsaturated fatty acids possess lower melting point than saturated fatty acids. Thus, most of the saturated fatty acids are solid at room temperature.

Answer to Problem 18.9E

The fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{\text{14}}{\text{H}}_{\text{24}}\right)\text{COOH}$ is an unsaturated fatty acid and it is a liquid at room temperature.

Explanation of Solution

The structural formula of fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{\text{14}}{\text{H}}_{\text{24}}\right)\text{COOH}$ is given below.

Figure 3

The general name of the above fatty acid is palmitolic acid. The structural formula of palmitolic acid contains double bonds within the fatty acid chain. Therefore, palmitolic acid is an unsaturated fatty acid. The side chain in unsaturated fatty acids possess less van der Waal’s interactions between side chains of adjacent molecule. Therefore, the unsaturated fatty acid is a liquid at room temperature.

Conclusion

The fatty acid shown in Figure 3 is an unsaturated fatty acid and it is a liquid at room temperature.

Interpretation Introduction

(d)

Interpretation:

Whether the fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{10}{\text{H}}_{\text{20}}\right)\text{COOH}$ is saturated or unsaturated is to be indicated and whether it is a solid or a liquid is to be stated.

Concept introduction:

A fatty acid having a long aliphatic chain with no double bond is called saturated fatty acid and a fatty acid that contains at least one double bond within the fatty acid chain is called unsaturated fatty acid. Due to the presence of a long alkyl side chain in saturated fatty acids, their packing efficiency is more than those of unsaturated fatty acids. As a result, unsaturated fatty acids possess lower melting point than saturated fatty acids. Thus, most of the saturated fatty acids are solid at room temperature.

Answer to Problem 18.9E

The fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{10}{\text{H}}_{\text{20}}\right)\text{COOH}$ is a saturated fatty acid and it is solid at room temperature.

Explanation of Solution

The structural formula of fatty acid ${\text{CH}}_{\text{3}}\left({\text{C}}_{10}{\text{H}}_{\text{20}}\right)\text{COOH}$ is given below.

Figure 4

The general name of the above fatty acid is lauric acid. Lauric acid has a long aliphatic chain of ${\text{-C}}_{\text{11}}{\text{H}}_{\text{23}}$ that follows the general formula of alkyl group $\left({\text{C}}_{\text{n}}{\text{H}}_{\text{2n+1}}\right)$. This shows that there is no double bond in the fatty acid chain. Therefore, the above fatty acid is a saturated fatty acid. Saturated fatty acid possesses a solid form due to favorable van der Waal’s interactions between side chains of adjacent molecule. Therefore, the saturated fatty acid is a solid at room temperature.

Conclusion

The fatty acid shown in Figure 4 is a saturated fatty acid and it is a solid at room temperature.