Question

Carnauba wax, used in floor and furniture polishes, contains an ester of a \(\mathrm{C}_{32}\) straight-chain alcohol with a \(\mathrm{C}_{20}\) straight- chain carboxylic acid. Draw its structure.

Short answer

Draw: \(\mathrm{CH}_3(\mathrm{CH}_2)_{30}\mathrm{OCO}(\mathrm{CH}_2)_{18}\mathrm{CH}_3\).

Step-by-step solution

Understanding the Components

The ester is formed from a reaction between a \(\mathrm{C}_{32}\) straight-chain alcohol and a \(\mathrm{C}_{20}\) straight-chain carboxylic acid. This means the alcohol has 32 carbon atoms and the acid has 20 carbon atoms in their main chains.

Identifying Functional Groups

Ensure you recognize the functional groups. The alcohol will have an \(-\mathrm{OH}\) group attached to one of the carbons, and the carboxylic acid will have a \(-\mathrm{COOH}\) group. When forming an ester, the \(-\mathrm{OH}\) from the carboxylic acid and \(-\mathrm{H}\) from the alcohol \(-\mathrm{OH}\) are removed as water.

Drawing the Alcohol

Draw the 32-carbon straight chain alcohol: \(\mathrm{CH}_3(\mathrm{CH}_2)_{30}\mathrm{CH}_2\mathrm{OH}\). This represents a linear chain of 32 carbon atoms ending with an \(-\mathrm{OH}\) group.

Drawing the Carboxylic Acid

Draw the 20-carbon straight chain carboxylic acid: \(\mathrm{CH}_3(\mathrm{CH}_2)_{18}\mathrm{COOH}\). This represents a linear chain of 20 carbon atoms ending with a \(-\mathrm{COOH}\) group.

Forming the Ester

Remove an \(-\mathrm{H}\) from the alcohol and an \(-\mathrm{OH}\) from the carboxylic acid to form water (\(\mathrm{H}_2\mathrm{O}\)). Connect the oxygen remaining on the alcohol to the carbon of the carboxyl group, forming an ester linkage. The structure is: \(\mathrm{CH}_3(\mathrm{CH}_2)_{30}\mathrm{O}\mathrm{CO}(\mathrm{CH}_2)_{18}\mathrm{CH}_3\).

Key concepts

Carnauba Wax

Carnauba wax is a natural wax derived from the leaves of the carnauba palm, which is native to Brazil. This wax is prized for its glossy finish and durability, making it a popular ingredient in products like floor and furniture polishes. It is composed of esters, free fatty acids, and alcohols, among other components.
One notable characteristic of carnauba wax is its high melting point, which makes it useful in applications requiring heat resistance. The ester in carnauba wax is a result of a chemical reaction between a \(\mathrm{C}_{32}\) straight-chain alcohol and a \(\mathrm{C}_{20}\) straight-chain carboxylic acid.
This structure contributes to the wax's hardness and its ability to form a solid film, helping protect surfaces and enhance shine.

Alcohol Structure

Alcohols are organic compounds that feature one or more hydroxyl groups (\(-\mathrm{OH}\)) attached to a carbon atom. Their general formula can be written as \(\mathrm{R-OH}\), where \(\mathrm{R}\) represents an alkyl group (a chain of carbon atoms).
In the case of carnauba wax, we deal with a \(\mathrm{C}_{32}\) straight-chain alcohol, meaning it consists of 32 carbon atoms in a row, ending with a hydroxyl group.
This can be depicted as: \(\mathrm{CH}_3(\mathrm{CH}_2)_{30}\mathrm{CH}_2\mathrm{OH}\). Here, the long hydrocarbon chain contributes to the overall hydrophobic nature of the compound, which is crucial for its role in waxes, where water repellency is desired.
Understanding the structure of alcohols helps grasp their behavior in esterification reactions, where the hydroxyl group plays a pivotal role.

Carboxylic Acid Structure

Carboxylic acids are another crucial class of organic compounds that feature a carboxyl group (\(-\mathrm{COOH}\)) attached to a carbon backbone. This group is what imparts the acidic nature of the compound.
The general structure can be represented as \(\mathrm{RCOOH}\), where \(\mathrm{R}\) is the hydrocarbon chain or a substituent group.
In the case of the ester in carnauba wax, the carboxylic acid involved has a linear chain of 20 carbon atoms: \(\mathrm{CH}_3(\mathrm{CH}_2)_{18}\mathrm{COOH}\).
The presence of the carboxyl group makes it reactive with alcohols, allowing them to form esters.
This functional group not only defines the chemical properties of carboxylic acids but also plays a key role in various biochemical processes and industrial applications. Recognizing the structure and functionalities of carboxylic acids aids in understanding their reactivity and the types of derivatives they can form, such as esters.