The main difference between aliphatic and aromatic carboxylic acid is that aliphatic carboxylic acids have a straight or branched chain as their core structure, whereas aromatic carboxylic acids contain a benzene ring as a part of their molecular structure.
Aliphatic and aromatic carboxylic acids are organic compounds. In fact, both have the same functional group, the carboxyl group (COOH).
Key Areas Covered
1. What is Aliphatic Carboxylic Acid
– Definition, Structure, Aromaticity
2. What is Aromatic Carboxylic Acid
– Definition, Structure, Aromaticity
3. Similarities Between Aliphatic and Aromatic Carboxylic Acid
– Outline of Common Features
4. Difference Between Aliphatic and Aromatic Carboxylic Acid
– Comparison of Key Differences
Key Terms
Aliphatic Carboxylic Acid, Aromatic Carboxylic Acid
What is Aliphatic Carboxylic Acid
Aliphatic carboxylic acid is characterized by the presence of a carboxyl functional group attached to an aliphatic carbon chain. An aliphatic carbon chain can be either straight or branched, and it may contain varying numbers of carbon atoms. Some examples of the aliphatic of aliphatic carboxylic acids include acetic acid, propionic acid, and butyric acid.
Carboxylic acids are acidic in nature. The carboxyl group within these compounds can donate a proton, making them weak acids. The carboxyl group contains a hydrogen atom that is readily ionizable, making aliphatic carboxylic acids weak acids. Besides, in aqueous solutions, they can partially dissociate, releasing hydrogen ions and forming carboxylate ions.
Figure 1: Propanoic Acid
Moreover, several factors influence the acidity of aliphatic carboxylic acids, including the electronic and steric effects of the alkyl group attached to the carboxyl carbon. The increasing electron-withdrawing nature of the alkyl group enhances the acidity of the carboxylic acid. For example, acetic acid is more acidic than ethyl acetic acid due to the greater electron-withdrawing effect of the methyl group in the acetic acid.
Carboxyl groups can also contribute to their high polarity. As a result, aliphatic carboxylic acids readily form hydrogen bonds with other polar molecules, which enhances their solubility in water. A factor that determines the solubility in water is the length of the carbon chain. As the carbon chain length increases, the solubility in water generally decreases. Another important chemical property of aliphatic carboxylic acid is its reactivity. They can undergo various chemical reactions, including acid-base reactions, esterification, oxidation, and decarboxylation.
Applications of Aliphatic Carboxylic Acids
Aliphatic carboxylic acids have various uses in the food industry. Acetic acid is used as a condiment and a preservative in various food products. It also contributes to the flavor and aroma of fruits, butter, cheese, and other dairy products. They are also used as pH regulators and acidulants in food and beverage production. In addition, they are also useful in the production of esters. In addition, they act as starting materials for the synthesis of drugs.
What is Aromatic Carboxylic Acid
Aromatic carboxylic acids are a class of organic compounds that contain both an aromatic ring and a carboxylic functional group in their molecular structure. One feature of this compound is the presence of the aromatic ring having carbon atoms arranged in a cyclic nature with alternating single and double bonds. The carboxyl group is attached to the aromatic ring typically at the ortho (1,2), meta(1,3), or para (1,4) position. Benzoic acid, salicylic acid, and phthalic acid are common examples of this group of compounds.
Moreover, one significant chemical property of aromatic carboxylic acids is their acidity. The carboxyl group in these compounds donates a proton, making them weak acids. The presence of an electron-withdrawing aromatic ring further enhances the acidity compared to aliphatic carboxylic acids. Benzoic acid, salicylic acid, and phthalic acid are common examples of aromatic carboxylic acids.
Figure 2: Benzoic Acid
Applications of Aromatic Carboxylic Acid
There are many applications of the aromatic carboxylic acids. Many drugs contain aromatic carboxylic acid moieties in their structures, which contribute to their therapeutic effects and interactions with biological targets. Salicylic acid is a key component of aspirin and is known for its anti-inflammatory and analgesic properties. Moreover, benzoic acid and its derivatives are commonly used as preservatives in pharmaceutical formulations due to their antimicrobial activity.
Aromatic carboxylic acids find applications in the development of agrochemicals, including herbicides, fungicides, and insecticides. They are also utilized in the production of high-performance polymers. Aromatic carboxylic acids serve as precursors in the production of dyes and pigments. Some aromatic carboxylic acids are natural constituents of food and beverages. They are also versatile starting materials in organic synthesis.
Similarities Between Aliphatic and Aromatic Carboxylic Acid
- Aliphatic and aromatic carboxylic acids are organic compounds.
- Both have the same functional group.
Difference Between Aliphatic and Aromatic Carboxylic Acid
Definition
Aliphatic carboxylic acids are organic compounds that contain a carboxyl functional group attached to an aliphatic carbon chain, while aromatic carboxylic acids are a class of organic compounds that contain both an aromatic ring and a carboxylic functional group in their molecular structure.
Structure
Aliphatic carboxylic acids have a straight or branched chain as their core structure, whereas aromatic carboxylic acids contain a benzene ring as a part of their molecular structure.
Aromaticity
Aromatic carboxylic acids possess an aromatic ring that exhibits resonance stabilization and increased stability due to the delocalization of electrons. Aliphatic carboxylic acids, on the other hand, lack an aromatic ring, resulting in the absence of resonance stabilization and the corresponding increased stability achieved through electron delocalization.
Solubility
Aliphatic carboxylic acids tend to be more soluble in water compared to aromatic carboxylic acids.
Conclusion
The main difference between aliphatic and aromatic carboxylic acid is that aliphatic carboxylic acids have a straight or branched chain as their core structure, whereas aromatic carboxylic acids contain a benzene ring as a part of their molecular structure.
Reference:
1. “Aromatic Acid.” Encyclopedia Britannica.
2. “Aliphatic Carboxylic Acids, Saturated.” Wiley Online Library.
Image Courtesy:
1. “Propanoic Acid Carboxylic Acid” (CC0) via Pixabay
2. “Benzoic acid structure” By Hindram – Own work (CC BY-SA 4.0) via Commons Wikimedia
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