Problem 30 - General Chemistry: Principles and Modern Applications

Question

Give the isomers with molecular formula \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}\) that contain more than one functional group.

Step-by-Step Solution

Answer

The isomers of \( C_{5} H_{10} O_{2} \) that contain more than one functional group are \( CH_{2}COOH-CH_{2}-CHO \), \( CH_{2}COOH-CH-CH_{2}-CHO \), and \( CH_{2}COO-CH_{2}-CHO \).

Step 1: Identify the Functional Groups

Functional groups that comprise the molecular formula \( C_{5} H_{10} O_{2} \) include: the Carboxyl group (-COOH), the Aldehyde group (-CHO), and the Ester group (-COOR). It's crucial to remember that a molecule can have more than one functional group.

Step 2: Construct Isomers

Now, start by creating isomers with more than one functional group: \n\n1. The first isomer contains one Carboxyl group and one Aldehyde group. This corresponds to a 4-carbon chain with a Carboxyl group at one end and an Aldehyde group at the other end: \( CH_{2}COOH-CH_{2}-CHO \).\n\n2. The second isomer contains one Carboxyl group and one Aldehyde group. This corresponds to a 5-carbon chain with a Carboxyl group at one end and an Aldehyde group in the middle of the chain: \( CH_{2}COOH-CH-CH_{2}-CHO \). \n\n3. The third isomer contains one Ester group and one Aldehyde group. This represents a 5-carbon chain with an Ester group in the middle and an Aldehyde group at one end: \( CH_{2}COO-CH_{2}-CHO \).

Step 3: Check for More Isomers

Rotate and rearrange atoms and bonds to ensure all possible isomers are found.

Key Concepts

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They help determine the properties and reactions of organic compounds. In the context of isomers, functional groups play a crucial role in defining different structural arrangements.

Common functional groups include:

• Alcohol (-OH)
• Aldehyde (-CHO)
• Carboxyl (-COOH)
• Ester (-COOR)
• Ketone (-C=O)

Each functional group contributes its own unique properties to the molecule. For example, the presence of a carboxyl group may make a molecule behave as an acid. Understanding these groups helps predict the kinds of reactions a molecule can undergo.

Carboxyl Group

The carboxyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group (-COOH). It is commonly found in organic acids, such as acetic acid and citric acid.

Characteristics of the carboxyl group include:

• Acidic nature due to the tendency to donate a hydrogen ion (H+).
• Polar, as the oxygen is more electronegative than carbon and hydrogen, making it susceptible to hydrogen bonding.
• Commonly found at the ends of the carbon chain in carboxylic acids.

The carboxyl group's ability to donate a proton (H+) makes it a key player in acid-base reactions. It plays a pivotal role in the formation of isomers, particularly when in conjunction with other functional groups like aldehydes.

Aldehyde Group

The aldehyde group is characterized by a carbon atom double-bonded to oxygen ('carbonyl' group) and single-bonded to hydrogen (—CHO). It typically appears at the end of a carbon chain. Aldehydes are known for their distinct smell and are often used in perfumes and flavorings.

Key points about aldehyde groups include:

• Positioned at the end of a molecule.
• Reactive due to the presence of the double-bonded oxygen.
• Often involved in oxidation reactions, converting to carboxylic acids.

When combined with other functional groups, such as in the formation of isomers, aldehydes can significantly alter the properties of a compound. This makes them highly versatile in organic synthesis.

Ester Group

An ester group is formed from a carboxylic acid and an alcohol and consists of a carbon double-bonded to an oxygen, and a single-bonded to an oxygen attached to another carbon (-COOR). Esters have a distinct sweet smell often associated with fruits.

Characteristics of esters include:

• Typically formed by the reaction between an alcohol and a carboxylic acid.
• Widely used in the production of fragrances and flavorings due to their pleasant aromas.
• Can also be hydrolyzed back into an alcohol and acid, showcasing their versatility.

In isomer formation, the ester group provides a unique structural arrangement with its distinct connectivity. Its ability to participate in various reactions adds to the complexity and potential variety of organic molecules.