Problem 87 - Chemistry The Central Science In Si Units

Question

Write a condensed structural formula for each of the following: (a) an amide with the formula \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{NO},(\mathbf{b})\) a cyclic ether with the formula \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O},(\mathbf{c})\) a diketone compound with the formula \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{2},\) (d) a phenyl carboxylic acid with the formula \(\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{2}\)

Step-by-Step Solution

Answer

(a) Condensed structure: \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CONH}_2 \), (b) \( \mathrm{O(CH}_2)_4 \), (c) \( \mathrm{CH}_3\mathrm{COCH}_2\mathrm{COCH}_3 \), (d) \( \mathrm{C}_6\mathrm{H}_5\mathrm{COOH} \).

Step 1: Identify the Amide

An amide containing the molecular formula \( \mathrm{C}_4 \mathrm{H}_9 \mathrm{NO} \) means it should have one nitrogen atom, one oxygen atom, and a likely arrangement of carbon and hydrogen consistent with this functional group. A simple option is butanamide: \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CONH}_2 \). This amide structure includes the required four carbon atoms, nine hydrogen atoms, one nitrogen, and one oxygen.

Step 2: Identify the Cyclic Ether

A cyclic ether with the formula \( \mathrm{C}_4 \mathrm{H}_8 \mathrm{O} \) is likely a tetrahydrofuran. Its structure is: \( \mathrm{O(CH}_2)_4 \), forming a five-membered ring where one member is oxygen and four are carbon.

Step 3: Identify the Diketone Compound

A diketone with the formula \( \mathrm{C}_5 \mathrm{H}_8 \mathrm{O}_2 \) could be 2,4-pentanedione. Its structure is \( \mathrm{CH}_3\mathrm{COCH}_2\mathrm{COCH}_3 \). This structure includes two ketone groups bonded by carbon atoms, fitting the molecular formula.

Step 4: Identify the Phenyl Carboxylic Acid

A phenyl carboxylic acid with the formula \( \mathrm{C}_7 \mathrm{H}_6 \mathrm{O}_2 \) could be benzoic acid: \( \mathrm{C}_6\mathrm{H}_5\mathrm{COOH} \). This structure has a benzene ring bonded to a carboxylic acid functional group, reflecting the given formula.

Key Concepts

Amide

Amides are a class of organic compounds characterized by having a nitrogen atom bonded to a carbonyl group. This key structural feature distinguishes them from other functional groups in organic chemistry. The general structure of an amide is written as \( RCONH_2 \) where \( R \) can be a alkyl, aryl, or another group. In an amide, the carbonyl (\( C=O \)) is directly linked to the nitrogen. This connection is crucial for its chemical behavior.
Amides can be found in a variety of forms, most commonly in the form of primary, secondary, or tertiary amides, depending on the number of alkyl or aryl groups attached to the nitrogen.

• Primary amides have one hydrogen atom bonded to the nitrogen (\( RCONH_2 \)).
• Secondary amides have two groups attached (\( RCONHR \)).
• Tertiary amides have three groups (\( RCONR_2 \)).

Amides are known for their roles in forming proteins, where they occur as peptide bonds, linking amino acids in living organisms. Additionally, they are often used in pharmaceuticals, polymers, and as solvents due to their stability and functional properties.

Cyclic Ether

Cyclic ethers are a class of organic compounds where an ether oxygen is part of a ring structure formed by atoms, typically carbon. The most typical cyclic ether is tetrahydrofuran (THF), with the formula \( \text{C}_4\text{H}_8\text{O} \), which features a five-membered ring consisting of four carbon atoms and one oxygen atom. This ring structure is notable for its stability and solubility properties.
Cyclic ethers are versatile in chemistry and industrial applications due to their unique structural properties:

• They can act as solvents for a wide range of chemical reactions.
• They serve as intermediates in synthesizing pharmaceutical and fine chemicals.
• They have a role as building blocks in polymer manufacture.

Cyclic ethers like tetrahydrofuran are often prized for their ability to dissolve polar and nonpolar compounds, which makes them particularly useful in various chemical syntheses.

Diketone

Diketones are organic compounds that contain two ketone (\( C=O \)) groups within their molecular structure. These compounds typically exhibit reactivity that is characteristic of ketones while also displaying unique properties due to the presence of two carbonyl functionalities. An example of a diketone is 2,4-pentanedione, formulated as \( \text{CH}_3\text{COCH}_2\text{COCH}_3 \).
The positioning of these ketone groups influences their reactivity. In each diketone structure, the carbonyl groups are connected by a hydrocarbon chain, which affects how they interact chemically:

• They participate in diverse coupling reactions, aiding in synthesizing larger organic molecules.
• They are utilized in forming chelation complexes in coordination chemistry.
• The diketone structure provides stability to metal-ion complexes, making them useful in various applications.

The ability of diketones to stabilize specific metal ions makes them valuable in analytical chemistry as well, where they can selectively bind and stabilize reaction intermediates.

Phenyl Carboxylic Acid

Phenyl carboxylic acids are organic compounds consisting of a carboxylic acid group attached to a phenyl ring. A classic example is benzoic acid, recognized by its chemical structure \( \text{C}_6\text{H}_5\text{COOH} \). These compounds are known for their aromatic property provided by the benzene ring that also affects their acidity.
Phenyl carboxylic acids like benzoic acid are integral in various fields:

• They serve as food preservatives, operating effectively due to their antibacterial properties.
• They are used in synthesizing various chemical intermediates, especially those where an aromatic moiety is desirable.
• These acids play a role in applications needing pH stabilization due to their buffering capabilities.

The presence of the benzene ring in these acids often enhances their reactivity and usefulness in synthetic organic chemistry, as it can undergo further substitution reactions under specific conditions, allowing for synthesis of a broad range of derivatives.