Question

Jojoba wax, used in candles and cosmetics, is partially composed of the ester of stearic acid and a straight-chain \(\mathrm{C}_{22}\) alcohol. Draw the structure of this ester.

Short answer

The ester structure is \( \text{CH}_3(\text{CH}_2)_{20}\text{COOCH}_2(\text{CH}_2)_{21}\text{CH}_3 \).

Step-by-step solution

Understand the components

To draw the ester, first identify what an ester is composed of. An ester results from the reaction of an alcohol and a carboxylic acid. In this exercise, the components are stearic acid and a 22-carbon alcohol.

Write the structural formulas

We need to consider the structural formulas of each component. Stearic acid is a fatty acid with the formula \( \text{C}_{17}\text{H}_{35}\text{COOH} \). The 22-carbon alcohol can be represented as \( \text{CH}_3(\text{CH}_2)_{21}\text{OH} \).

Step Formation of the ester

In an esterification reaction, the hydroxyl group \( (-OH) \) from the carboxylic acid reacts with the hydrogen from the alcohol \( (-OH) \) group, releasing water and forming an ester bond \((-COO-)\).

Draw the ester structure

The ester formed will have the following structure: \( \text{CH}_3(\text{CH}_2)_{20}\text{COOCH}_2(\text{CH}_2)_{21}\text{CH}_3 \). Here, the ester linkage \( (-COO-) \) connects the \( \text{C}_{17} \) carbon chain and the \( \text{C}_{22} \) alcohol chain.

Key concepts

Stearic Acid

Stearic acid is a type of saturated fatty acid, an important component in many natural substances. It is commonly found in animal and plant fats, making it a key ingredient in a variety of products. Its chemical formula is \( \text{C}_{17}\text{H}_{35}\text{COOH} \), where the "COOH" represents the carboxyl group, responsible for its acidic nature. The presence of a long hydrocarbon chain gives stearic acid its hydrophobic characteristics, meaning it does not dissolve well in water.

Stearic acid is widely used in the creation of esters because it provides a hydrophobic end and a reactive carboxyl end. In reactions, particularly esterification, stearic acid reacts with alcohols to form esters, releasing water as by-product. This reaction is useful in making soaps, cosmetics, candles, and other products that require stable, long-lasting structures.

C22 Alcohol

A \( \text{C}_{22} \) alcohol, also known as behenyl alcohol, is an alcohol with 22 carbon atoms in a straight chain. Its molecular formula is \( \text{CH}_3(\text{CH}_2)_{21}\text{OH} \). The presence of the long hydrocarbon tail in the structure is important for giving the alcohol its characteristic properties such as strength and waxy texture.

In esterification reactions, C22 alcohol acts as the alcohol component. The hydroxyl group (\( -OH \)) at the alcohol's terminal is crucial as it participates in forming ester bonds with acids. Its long carbon chain contributes to the increased hydrophobicity, making it useful for creating products that are less likely to dissolve in water. This is why C22 alcohol is often used in products like skin creams and conditioners, providing a non-greasy feel and protective barrier.

Chemical Structure Drawing

Drawing chemical structures can seem daunting, but it's crucial for understanding molecular compositions and chemical reactions. To draw complex molecules, such as those involved in esterification, it's important to start by identifying the key components involved.

Each molecule, whether it’s a fatty acid like stearic acid or a long-chain alcohol such as \( \text{C}_{22} \) alcohol, has specific structural formulas. For stearic acid, it is \( \text{C}_{17}\text{H}_{35}\text{COOH} \), while for the \( \text{C}_{22} \) alcohol, it is \( \text{CH}_3(\text{CH}_2)_{21}\text{OH} \). The formation of esters involves the linkage of these structures via the ester bond \(( -COO- )\).

• Identify each functional group, like the carboxyl for acids or hydroxyl for alcohols.
• Illustrate the long carbon chains accurately, noting any substitutions or linkages.
• Show the ester bond by connecting the carboxyl and hydroxyl groups.

Practicing these steps can enhance your ability to draw chemical structures and understand their formation in chemical processes.