The carbonyl stretch for caffeic acid is unusually low for a carboxylic acid at 1646 cm-1. For reference, the carbonyl stretch for propanoic acid is 1716 cm-1. Explain why the carbonyl stretch occurs at a lower wavenumber for caffeic acid.

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Keeping with the theme of autumn, one of Dr. Danahy’s favorite molecules is caffeic acid due to its presence in pumpkins. This structure serves as an antioxidant and is one of many found within pumpkins. Despite its name, it bears no resemblance to caffeine. Answer the following questions about caffeic acid.

The carbonyl stretch for caffeic acid is unusually low for a carboxylic acid at 1646 cm-1. For reference, the carbonyl stretch for propanoic acid is 1716 cm-1. Explain why the carbonyl stretch occurs at a lower wavenumber for caffeic acid.

The image shows the chemical structure of propanoic acid. 

**Structure Explanation:**
- The central feature of the structure is a three-carbon chain.
- The first carbon (from the left) is connected to two hydrogen atoms.
- The middle carbon is double-bonded to an oxygen atom (forming a carbonyl group, C=O).
- The same middle carbon is also single-bonded to a hydroxyl group (OH).
- This configuration indicates the presence of a carboxylic acid functional group, characteristic of propanoic acid.

**Chemical Name:**
- Propanoic acid

**Molecular Formula:** 
- C₃H₆O₂

This diagram is often used to teach the structural representation of carboxylic acids, emphasizing the functional group orientation that defines their chemical properties. Propanoic acid is commonly used in the food and plastic industries as a preservative and intermediate.
Transcribed Image Text:The image shows the chemical structure of propanoic acid. **Structure Explanation:** - The central feature of the structure is a three-carbon chain. - The first carbon (from the left) is connected to two hydrogen atoms. - The middle carbon is double-bonded to an oxygen atom (forming a carbonyl group, C=O). - The same middle carbon is also single-bonded to a hydroxyl group (OH). - This configuration indicates the presence of a carboxylic acid functional group, characteristic of propanoic acid. **Chemical Name:** - Propanoic acid **Molecular Formula:** - C₃H₆O₂ This diagram is often used to teach the structural representation of carboxylic acids, emphasizing the functional group orientation that defines their chemical properties. Propanoic acid is commonly used in the food and plastic industries as a preservative and intermediate.
**Caffeic Acid Chemical Structure**

The image illustrates the chemical structure of caffeic acid. This compound is classified as a hydroxycinnamic acid, naturally occurring in plants.

**Diagram Explanation:**

- **Phenolic Ring:** The structure features a benzene ring with two hydroxyl groups (OH) attached at the 3rd and 4th positions. This arrangement is common in phenolic compounds.
  
- **Side Chain:** A vinyl group (-CH=CH-) connects to the benzene ring at the 1st position and extends to a carboxyl group (COOH).

- **Functional Groups:**
  - **Hydroxyl Groups (OH):** Two are attached to the benzene ring, contributing to its antioxidant properties.
  - **Carboxyl Group (COOH):** Located at the end of the side chain, contributes to the acid's reactivity.

Caffeic acid is known for its antioxidant, anti-inflammatory, and potential therapeutic properties. It is commonly studied in the context of nutrition and health sciences.
Transcribed Image Text:**Caffeic Acid Chemical Structure** The image illustrates the chemical structure of caffeic acid. This compound is classified as a hydroxycinnamic acid, naturally occurring in plants. **Diagram Explanation:** - **Phenolic Ring:** The structure features a benzene ring with two hydroxyl groups (OH) attached at the 3rd and 4th positions. This arrangement is common in phenolic compounds. - **Side Chain:** A vinyl group (-CH=CH-) connects to the benzene ring at the 1st position and extends to a carboxyl group (COOH). - **Functional Groups:** - **Hydroxyl Groups (OH):** Two are attached to the benzene ring, contributing to its antioxidant properties. - **Carboxyl Group (COOH):** Located at the end of the side chain, contributes to the acid's reactivity. Caffeic acid is known for its antioxidant, anti-inflammatory, and potential therapeutic properties. It is commonly studied in the context of nutrition and health sciences.
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