Question

Draw and name the following: (a) The eight carboxylic acids with the formula \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\) (b) Three nitriles with the formula \(\mathrm{C}_{5} \mathrm{H}_{7} \mathrm{~N}\)

Short answer

Eight carboxylic acids: e.g., hexanoic acid, cyclopentane carboxylic acid. Three nitriles: e.g., pentanenitrile.

Step-by-step solution

Understand the task

We need to identify all possible carboxylic acids with the molecular formula \(\mathrm{C}_{6}\mathrm{H}_{12}\mathrm{O}_{2}\). This involves varying the carbon chain configuration and positioning of the carboxyl functional group. Similarly, find nitriles for the given formula \(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{~N}\).

Generate carboxylic acids

Identify the isomers of hexanoic acid. Begin with the straight-chain form: hexanoic acid, followed by isomers with branching in the carbon chain. Consider substituents like methyl or ethyl groups at different positions to form 2-methylpentanoic acid, 3-methylpentanoic acid, and similar setups for other positions.

List carboxylic acids

1. Hexanoic acid \((\mathrm{C}_6\mathrm{H}_{11}\mathrm{COOH})\)2. 2-Methylpentanoic acid \((\mathrm{C}_5\mathrm{H}_{9}\mathrm{(CH_3)COOH})\)3. 3-Methylpentanoic acid \((\mathrm{CH_3CH_2CH(CH_3)CH_2COOH})\)4. 4-Methylpentanoic acid \((\mathrm{CH_3(CH_2)2CH(CH_3)COOH)})\)5. 2-Ethylbutanoic acid \((\mathrm{C}_4\mathrm{H}_{8}\mathrm{(CH_2CH_3)COOH})\)6. 3-Ethylbutanoic acid \((\mathrm{C}_4\mathrm{H}_{7}\mathrm{(CH_2CH_2CH_3)COOH})\)7. Cyclopentane carboxylic acid \((\mathrm{C_5H_9COOH})\)8. 2,2-Dimethylbutanoic acid \((\mathrm{CH}(CH_3)_3CH_2COOH)\)

Generate nitriles

For nitriles, the formula \(\mathrm{C_5H_7N}\) indicates different carbon chain arrangements along with a \(\mathrm{C\equiv N}\) group. Identify different structures by considering variations in the positioning of an alkyl and cyano group within a 5-carbon framework.

List nitriles

1. Pentanenitrile \((\mathrm{C_5H_9CN})\)2. 3-Methylbutanenitrile \((\mathrm{C_4H_7CH(CN)CH_3})\)3. 2-Butenenitrile \((\mathrm{CH_3\mathrm{C(CH_2CH)CN})})\) or 3-Methyl-2-butenenitrile \(\mathrm{CH_3C(CH_2)C(CH_3)CN)}\)

Name verification

Check each name and structure to confirm no duplication and proper alignment with IUPAC naming conventions for both groups: carboxylic acids and nitriles.

Key concepts

Carboxylic Acids

Carboxylic acids are organic compounds that contain a carboxyl group (-COOH). They are known for their acidic properties due to the hydrogen atom attached to the oxygen in the carboxyl group. This hydrogen is easily lost as a proton, making carboxylic acids acidic in nature.
In the context of the exercise, we're dealing with carboxylic acids with a molecular formula of \(\mathrm{C}_{6}\mathrm{H}_{12}\mathrm{O}_{2}\). This indicates carbon chains with six carbons and potential branching, all featuring the carboxyl group.
Features of carboxylic acids:

• Soluble in water due to hydrogen bonding
• Higher boiling points than other hydrocarbons of similar size
• Strong enough to react with bases

These properties are influenced by the prominent carboxyl group, a fundamental element in organic synthesis and functional group transformations.

Nitriles

Nitriles are organic compounds containing a cyano group (-C≡N), which consists of a carbon triple-bonded to a nitrogen atom. This functional group is crucial for various chemical reactions and serves as an intermediate in organic synthesis.
The exercise involves nitriles with a molecular formula of \(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}\), providing flexibility in carbon chain arrangement alongside the cyano group.
Key aspects of nitriles:

• Have relative stability due to the strong carbon-nitrogen triple bond
• Used as precursors to carboxylic acids, amines, and other functional groups
• Nitriles typically exhibit high boiling points and can form hydrogen bonds through the nitrogen atom

These characteristics make nitriles an essential element in pharmaceuticals and materials science.

IUPAC Naming

The International Union of Pure and Applied Chemistry (IUPAC) provides the systematic approach to naming organic compounds. For both carboxylic acids and nitriles, IUPAC naming ensures clarity and standardization in chemical communication.
Carboxylic acids are named following the longest carbon chain containing the carboxyl group, ending with the suffix '-oic acid'. Nitriles are named similarly but end with '-nitrile'.
When naming compounds:

• Identify the longest carbon chain
• Locate and number substituents if applicable
• Use appropriate prefixes (e.g., 'ethyl' or 'methyl') for branching

Adhering to IUPAC rules is crucial for understanding and communicating chemical structures globally.

Molecular Formula

The molecular formula of a compound gives the exact number of different atoms present. It doesn't provide connectivity information but is essential for identifying possible isomers.
In this exercise, the two molecular formulas \(\mathrm{C}_{6}\mathrm{H}_{12}\mathrm{O}_{2}\) and \(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}\) lead to possible isomers, each conforming to these formulas, while varying in structural organization.
Here’s what you should know about molecular formulas:

• They reveal the proportion of atoms but not the structure
• Enable calculation of molar mass
• Serve as a start point for deriving structural formulas

Understanding molecular formulas helps in inferring basic compound properties and methods for synthesis.

Structural Isomers

Structural isomers share the same molecular formula but differ in the connectivity of their atoms. This results in different chemical and physical properties, and they are significant in forming a diverse array of compounds from a single set of elements.
For example, the molecular formula \(\mathrm{C}_{6}\mathrm{H}_{12}\mathrm{O}_{2}\) can generate isomers with varying lengths and branching of the carbon backbone, all maintaining the carboxyl functional group. Similarly, \(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}\) nitriles present multiple structural configurations.
Points to consider about structural isomers:

• They can dramatically differ in properties like boiling point or reactivity
• Configuration changes include different carbon chains, functional groups, and positions
• Understanding isomerism is crucial for synthetic chemistry and material science

Structural isomers enrich chemical diversity and knowledge, playing a critical role in developing new compounds and understanding their uses.