Introduction

Relevance of the Topic

The study of Carboxylic Acid Nomenclature is an essential aspect within the vast field of Organic Chemistry, as it allows for the correct identification and naming of compounds containing the COOH functional group. The importance of these acids in everyday life is incalculable, as they are involved in biological reactions, syntheses of organic compounds, and even in the formation of acid rain. Mastering the nomenclature of carboxylic acids is, therefore, a crucial step for a deep understanding of Chemistry.

Contextualization

This section is part of the broader scope of Organic Chemistry, following the study of basic organic functions (alkanes, alkenes, alkynes, alcohols, ethers, and amines). From this prior knowledge, the understanding of the characteristics and nomenclature patterns of carboxylic acids becomes clearer and more fluid. Moreover, the subject matter here serves as a basis for subsequent topics, such as Esterification Reaction and Saponification, increasing the complexity of knowledge in Organic Chemistry.

Theoretical Development

Components

• Carboxylic Acid Functional Group (COOH): Central component for the identification of carboxylic acids. Formed by a double bond between carbon and oxygen (carboxylic bond) and a single bond between oxygen and hydrogen (hydroxyl bond). Its presence confers acidic properties to the compound.

• Prefix and Suffix in Nomenclature: They are determinants for the identification and distinction of carboxylic acids. The prefix is obtained from the main chain and the suffix is always "oic". The main chain is the longest one containing the carboxylic group.

• Location of the Carboxylic Group: When the main chain contains more than two carbons, the position of the COOH group must be indicated. The carbon where the COOH group is located is carbon number 1.

Key Terms

• Alkyl Chain: It is a linear sequence of unbranched carbons (alkane). It can be of any length in a carboxylic acid, with the carbon where the carboxylic group is located being carbon number 1.

• Radical: It is a segment of a molecule that remains after an atom is removed. In carboxylic acids, the radical is the name given to the part of the molecule that does not contain the COOH group.

• Monovalence: It is the ability of an atom to combine with only one atom of an element or with only one group (-OH, -Cl, -NH2, etc.). This is important in the nomenclature of carboxylic acids, as the hydrogen in the COOH group is monovalent.

Examples and Cases

• Methanoic Acid (Formic): The smallest of the carboxylic acids. Its molecular formula is HCOOH. The name "methanoic" is derived from methane (which is the main chain with 1 carbon) and adding the suffix "oic" to indicate the presence of the carboxylic group.

• Ethanoic Acid (Acetic): Has 2 carbons in the main chain (ethane). The molecular formula is CH3-COOH. The name "ethanoic" is derived from ethane (main head with 2 carbons) and adding the suffix "oic" to indicate the presence of the carboxylic group.

• Propanoic Acid (Propionic): Has 3 carbons in the main chain (propane). The molecular formula is CH3-CH2-COOH. The name "propanoic" is derived from propane (main head with 3 carbons) and adding the suffix "oic" to indicate the presence of the carboxylic group.

• Butanoic Acid (Butyric): Has 4 carbons in the main chain (butane). The molecular formula is CH3-CH2-CH2-COOH. The name "butanoic" is derived from butane (main head with 4 carbons) and adding the suffix "oic" to indicate the presence of the carboxylic group.

• Pentanoic Acid (Valeric): Has 5 carbons in the main chain (pentane). The molecular formula is CH3-(CH2)3-COOH. The name "pentanoic" is derived from pentane (main head with 5 carbons) and adding the suffix "oic" to indicate the presence of the carboxylic group.

• Hexanoic Acid (Caproic): Has 6 carbons in the main chain (hexane). The molecular formula is CH3-(CH2)4-COOH. The name "hexanoic" is derived from hexane (main head with 6 carbons) and adding the suffix "oic" to indicate the presence of the carboxylic group.

Detailed Summary

Relevant Points

• Composition of Carboxylic Acid (COOH): Carboxylic acids are characterized by the presence of the COOH functional group. This group is formed by a double bond between a carbon and an oxygen (carboxylic bond) and a single bond between an oxygen and a hydrogen (hydroxyl bond), giving the compound acidic properties.

• Prefix and Suffix in Nomenclature: The nomenclature of carboxylic acids is defined from the prefix that indicates the number of carbons in the main chain (each carbon is represented by the suffix "ane") and the suffix is always "oic". Knowledge of these terms and their respective applications is crucial for the correct naming of the compounds.

• Location of the Carboxylic Group: When the main chain contains more than two carbons, the position of the COOH group must be indicated. In this case, the carbon to which the group is attached is considered carbon number 1.

• Practical Examples: The formic, acetic, propionic, butyric, valeric, and caproic acids are practical examples of carboxylic acids. Analyzing their molecular structures and how they are named helps to consolidate the understanding of the subject.

Conclusions

• The nomenclature of carboxylic acids follows specific rules based on the prefix (indicating the number of carbons in the main chain), and the suffix "oic". Learning and mastering these rules is essential for the correct identification of the compounds.

• The location of the carboxylic group is also relevant information in the nomenclature. When necessary, the position of the carboxylic group (carbon 1) in the main chain must be indicated.

• The practice of identifying and naming carboxylic acids with different carbon chains facilitates the learning and memorization process.

Suggested Exercises

1. Name the carboxylic acid whose molecular formula is C3H6O2 and indicate the number of carbons in its main chain.

2. Write the molecular formula of butanoic acid and indicate the number of carbons in its main chain.

3. Indicate the number of carbons in the main chain and give the name of the carboxylic acid with the molecular formula CH3(CH2)5COOH.

4. Write the nomenclature of ethanoic acid. What is its molecular formula?

5. Propanoic acid is a low molecular weight organic compound. Describe the structure of this compound, indicating the position of the carboxylic group.