Question

Draw and name compounds that meet these descriptions: (a) Three different amides with the formula \(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{NO}\) (b) Three different esters with the formula \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\)

Short answer

Three amides: pentamide, 2-methylbutanamide, 3-methylbutanamide. Three esters: ethyl butanoate, methyl pentanoate, propyl propanoate.

Step-by-step solution

Understanding the Problem

We are asked to draw and name chemical compounds with specified molecular formulas. For part (a), we need to find three different amides with the formula \( \mathrm{C}_{5} \mathrm{H}_{11} \mathrm{NO} \), and for part (b), three different esters with the formula \( \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2} \). Amides are characterized by the functional group \( -CONH_2 \), while esters have the functional group \(-COOR\).

Part (a) – Drawing Amides

To find amides with the formula \( \mathrm{C}_{5} \mathrm{H}_{11} \mathrm{NO} \), we must identify possible acyl groups combined with amine groups. Three possible structures are:1. **Pentamide**: A linear chain with a terminal amide group: CH₃CH₂CH₂CH₂CONH₂.2. **2-Methylbutanamide**: A branched chain: (CH₃)₂CHCH₂CONH₂.3. **3-Methylbutanamide**: Another branched version: CH₃CH(CH₃)CH₂CONH₂.

Naming the Amides

Each amide named reflects the longest chain attached directly to the amide group: 1. "Pentamide" (n-pentanamide): the unbranched chain. 2. "2-Methylbutanamide": a methyl group on the second carbon. 3. "3-Methylbutanamide": a methyl group on the third carbon.

Part (b) – Drawing Esters

For esters with the formula \( \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2} \), we focus on the ester group \(-COOR\). Three possible structures are:1. **Ethyl butanoate**: Linear with ethyl group: CH₃CH₂CH₂COOCH₂CH₃.2. **Methyl pentanoate**: Linear with methyl group: CH₃CH₂CH₂CH₂COOCH₃.3. **Propyl propanoate**: Formed by a propyl group: CH₃CH₂COOCH₂CH₂CH₃.

Naming the Esters

Each ester is named by specifying the alkyl group from the alcohol and the acid group from the carboxylic acid: 1. "Ethyl butanoate": Ethyl from alcohol, butanoate from the acid. 2. "Methyl pentanoate": Methyl from alcohol, pentanoate from the acid. 3. "Propyl propanoate": Propyl from alcohol, propanoate from the acid.

Key concepts

Functional Groups

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They're like the active players in chemical interactions. Common functional groups include:

• Hydroxyl Group \((-OH)\)
• Carbonyl Group \((-C=O)\)
• Amide Group \((-CONH_2)\)
• Ester Group \((-COOR)\)

Each functional group imparts a distinct set of properties to the organic compound. They help in categorizing and predicting the reactions of compounds. For example, both amides and esters have the carbonyl group, but their behavior in reactions can differ because of how the carbonyl is connected to other atoms.
Recognizing functional groups is key to understanding structure and reactivity in organic molecules.

Amide Compounds

Amide compounds are characterized by the presence of an amide group. This group consists of a carbonyl group bonded to a nitrogen atom \((-CONH_2)\). They are typically formed by the reaction between a carboxylic acid and an amine.

Amides can appear as primary, secondary, or tertiary:

• Primary Amides: One hydrogen atom with the amine group \(\text{(RCONH}_2\))\.
• Secondary Amides: Two alkyl groups attached to the nitrogen \(\text{(RCONHR')}\).
• Tertiary Amides: Three alkyl groups bonded to nitrogen \(\text{(RCONR'}_2)\).

These compounds are found in various natural products and synthetic materials. They are known for their roles in pharmaceuticals, plastics, and dyes. Understanding amide structures helps in identifying their chemical properties and uses.

Ester Compounds

Ester compounds are characterized by the ester functional group, which consists of a carbonyl group linked to an alkoxy group \((-COOR)\). They are typically derived from an acid (most often a carboxylic acid) and an alcohol.

Properties and uses:

• Characteristic Aroma: Many esters have pleasant fruity smells; they're used in perfumes and flavorings.
• Biodegradable: Used in making biodegradable plastics.
• Simplified Structure: Easier to break down than carboxylic acids, enabling diverse uses in organic synthesis.

In chemistry, naming esters involves the alcohol part first (using the alkyl group name), followed by the acid part turned into an -oate suffix. For example, ethyl ethanoate (or ethyl acetate) is a common ester used in solvents.

Chemical Nomenclature

Chemical nomenclature refers to the system used for naming chemical compounds. This helps in communication among chemists by providing standardized names for chemical substances.

Essential rules in naming organic compounds:

• Identify Longest Chain: Find the longest carbon chain to name the base of the compound.
• Number the Chain: Assign numbers to carbon atoms, beginning from the end closest to any substituent group.
• Functional Groups: Use prefixes/suffixes for functional groups (e.g., -ol for alcohols, -oate for esters).
• Substituents: Indicate any side chains or variations in structure, such as methyl or ethyl, and their positions.

This system ensures clarity and precision in describing chemical compounds, minimizing confusion over compound structure and function. Understanding chemical nomenclature is crucial for anyone studying or working in the field of chemistry.