Question

Propose structures that meet the following descriptions: (a) A ketone with five carbons (b) A four-carbon amide (c) A five-carbon ester (d) An aromatic aldehyde (e) A keto ester (f) An amino alcohol

Short answer

(a) Pentan-2-one, (b) Butanamide, (c) Ethyl propanoate, (d) Benzaldehyde, (e) Ethyl acetoacetate, (f) Ethanolamine.

Step-by-step solution

Understanding the Request

First, we need to interpret what each description means in terms of chemical structure and functional groups. For each description, identify the necessary functional groups: 1. Ketone: Contains a carbonyl group (C=O) within a carbon chain.2. Amide: Contains a carbonyl group connected to a nitrogen (\(R-C(=O)-NR_2\)).3. Ester: Contains the functional group \(R-C(=O)-OR'\).4. Aromatic Aldehyde: Contains an aldehyde group \(R-C(=O)H\) attached to an aromatic ring.5. Keto Ester: Contains both a ketone \(R-C(=O)-R'\) and an ester group.6. Amino Alcohol: Contains both an amino \(NH_2\) and an alcohol \(R-OH\) group.

Five-Carbon Ketone

For a ketone with five carbons, draw a structure with a carbonyl group flanked by carbon chains. An example is pentan-2-one, which has the structure: \[ \text{CH}_3-\text{CO}-\text{CH}_2-\text{CH}_2-\text{CH}_3 \] The carbonyl group is positioned on the second carbon.

Four-Carbon Amide

For a four-carbon amide, draw a structure containing an amide group. An example is butanamide, which has the structure: \[ \text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CONH}_2 \] This includes the amide linkage at the end of a three-carbon chain.

Five-Carbon Ester

For a five-carbon ester, draw an ester structure. Example: ethyl propanoate, which has the structure: \[ \text{CH}_3-\text{CH}_2-\text{C(=O)-O-CH}_2-\text{CH}_3 \] The ester linkage connects a two-carbon group to a three-carbon group.

Aromatic Aldehyde

For an aromatic aldehyde, connect an aldehyde group to a benzene ring, such as benzaldehyde. Its structure is: \[ \text{C}_6\text{H}_5-\text{CHO} \] where the aldehyde group is directly attached to the aromatic ring.

Keto Ester

A keto ester contains both a ketone and an ester. An example is ethyl acetoacetate, with structure: \[ \text{CH}_3-\text{CO-CH}_2-\text{COOCH}_2-\text{CH}_3 \]. This molecule has a ketone and an ester group on adjacent carbons.

Amino Alcohol

An amino alcohol is characterized by both an amino and an alcohol functional group. An example is ethanolamine, with structure: \[ \text{HO-CH}_2-\text{CH}_2-\text{NH}_2 \]. The amino group is adjacent to the alcohol group.

Key concepts

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic chemical behaviors. Understanding these groups is vital in organic chemistry because they dictate how a chemical compound behaves. In the exercise, various functional groups are highlighted:

• Ketones: These contain a carbonyl group (C=O) within a carbon chain. They're known for their reactivity and presence in many biological processes.
• Amides: Featuring a carbonyl group linked to a nitrogen atom (\(R-C(=O)-NR_2\)), amides are common in proteins, serving as a backbone structure of peptides.
• Esters: These contain the group \(R-C(=O)-OR'\) and are responsible for many natural fragrances and flavors.
• Aromatic Aldehydes: Aldehyde groups (\(R-C(=O)H\)) attached to aromatic rings are found in essential oils and perfumes.
• Keto Esters: These compounds have both ketone (\(R-C(=O)-R'\)) and ester groups, illustrating complex reactivity.
• Amino Alcohols: Containing both amino (\(NH_2\)) and alcohol (\(R-OH\)) groups, these are prevalent in biochemical systems.

Recognizing these functional groups and their layouts helps predict the behaviors and reactions of organic molecules.

Chemical Structure

Chemical structure is the arrangement of atoms in a molecule in three-dimensional space, explaining the molecule's properties and functions. Each exercise problem seeks various arrangements utilizing known chemical structures:

• Pentan-2-one: A five-carbon ketone where the carbonyl group is at the second position. It illustrates how placement affects molecule reactivity.
• Butanamide: A four-carbon chain featuring an amide group at the terminal end, showing typical amide linkages in peptides.
• Ethyl propanoate: Demonstrates an ester with a five-carbon chain showcasing esterification's significance in forming scents.
• Benzaldehyde: An archetypal aromatic aldehyde, its benzene ring highlights resonance stability, essential in organic chemistry.
• Ethyl acetoacetate: Exemplifies a keto ester with ketone and ester groups, used often in synthesis due to its reactive properties.
• Ethanolamine: This demonstrates an amino alcohol, critical for studying alcohols’ and amines’ properties in organic molecules.

Understanding chemical structures is pivotal for predicting reactions and properties of organic substances.

Organic Molecules

Organic molecules primarily comprised of carbon, hydrogen, and other elements like nitrogen, oxygen, or sulfur define the vast world of organic chemistry. In our exercise, each described compound serves as an example of diverse types of organic molecules:

• Aliphatic Molecules: Like pentan-2-one and butanamide, these are part of a vast category characterized by straight or branched chains without aromatic rings.
• Aromatic Compounds: Exposed in benzaldehyde, aromaticity provides compounds with unique stability and reactivity due to electron delocalization.
• Complex Compounds: Such as keto esters (ethyl acetoacetate), display how combining functional groups creates molecules pivotal in synthetic chemistry.

Learning about these molecules’ structures allows for a better understanding of how organic chemistry principles apply in real-world applications, from medicine to materials.

Problem Solving

Problem-solving in organic chemistry involves translating complex compound descriptions into tangible chemical structures. In this exercise, each part emphasized a clear problem-solving approach:

• Identification of Functional Groups: Begin by discerning the necessary functional group for the given description.
• Sketch the Carbon Skeleton: Use the number of carbons specified to draft the molecule’s backbone.
• Integrate Functional Groups: Position functional groups accurately within the carbon framework.
• Verify Stability and Correctness: Adjust to ensure all valencies are satisfied, cross-check with known chemical rules.

Developing proficiency in these techniques fosters more significant insights into chemical behavior, preparation for complex problem-solving, and application in synthetic design and reactions.