Introduction

Relevance of the Theme

Ketone is one of the essential organic functions in the study of Organic Chemistry. It is present in a variety of biologically and industrially important compounds, such as acetone, the main representative of ketones and one of the most widely used solvents in the world. Understanding its characteristics, nomenclature, and reactivity provides a solid foundation for exploring more advanced topics in organic chemistry, such as oxidation reactions, nucleophilic addition, among others.

Contextualization

In the scope of the Chemistry discipline, the study of organic functions, including ketones, emerges after understanding the main carbon structures and hydrocarbons. Ketones, which belong to the carbonyl group, are a crucial link between hydrocarbons and other functional groups such as alcohols, ethers, and carboxylic acids, playing a fundamental role in the chemistry of organic compounds. This lecture note aims to solidify the understanding of key concepts about ketones, such as their structure, how to identify them, nomenclature, and examples of reactions.

Theoretical Development

Components

• Carbonyl Functional Group: Located in the center of a ketone molecule, the carbonyl (C=O) is a key group for identifying a ketone. It consists of a carbon atom bonded to two oxygen atoms, with one of the oxygens bonded to a carbon or hydrogen atom (corresponding, respectively, to a secondary or tertiary ketone).

• Classification: Ketones are classified according to the number of carbon-carbon bonds of the carbonyl carbon. Ketones with the carbonyl carbon bonded to two other carbon atoms are called secondary ketones, while ketones with the carbonyl carbon bonded to a hydrogen atom and a carbon atom are called primary ketones. Ketones with the carbonyl carbon bonded only to other carbons are tertiary ketones.

• Nomenclature and Identification: Ketones are identified by the suffix 'one' in the official IUPAC nomenclature after naming the main chain, which includes the position of the carbonyl. In common nomenclature, we use the names of the radicals bonded to the carbonyl, followed by the word 'ketone'.

Key Terms

• Ketone: Organic functional group consisting of a carbon atom bonded to the carbonyl (C=O) and two other groups of atoms.

• Primary Ketone: A ketone in which the carbonyl carbon is bonded to a hydroxyl and a hydrogen.

• Secondary Ketone: A ketone in which the carbonyl carbon is bonded to two carbon groups.

• Tertiary Ketone: A ketone in which the carbonyl carbon is bonded to a hydrogen and two carbon groups.

Examples and Cases

• Acetone: Acetone (CH3COCH3) is the simplest ketone and one of the most widely used solvents in the world. It is a secondary ketone, where the two carbons bonded to the carbonyl have only single bonds with other carbon atoms.

• Propanone: Also known as dimethyl ketone, is a secondary ketone. It has a chain of three carbons with a carbonyl in the middle.

• Butanone: Also known as methyl ethyl ketone, is a secondary ketone. It has a chain of four carbons with a carbonyl in the middle.

• Pentanone: Also known as methyl propyl ketone, is a secondary ketone. It has a chain of five carbons with a carbonyl in the middle.

In all examples, it is important to note that the carbons bonded to the carbonyl are secondary, as they are bonded to two other carbon atoms. Knowledge of these examples will help identify and name other ketones in problems and exercises.

Detailed Summary

Key Points

• Definition and Structure of Ketone: Ketone is a functional type consisting of a carbonyl group (C=O) bonded to two carbon atoms. The carbonyl, located in the center of the molecule, is essential for identifying a ketone.

• Classification of Ketones: Ketones are classified according to the number of carbon atoms directly bonded to the carbonyl. Primary, secondary, and tertiary ketones are those where the carbonyl carbon is, respectively, bonded to a hydrogen and a carbon, to two carbons, or to three carbons.

• Ketone Nomenclature: Ketones are named by adding the suffix 'one' in IUPAC, after naming the main chain that includes the position of the carbonyl group. In common nomenclature, the name of the radicals bonded to the carbonyl is preceded by the word 'ketone'.

• Examples of Ketones: Acetone (CH3COCH3), propanone, butanone, and pentanone are secondary ketones with, respectively, two, three, four, and five carbon bonds in total.

Conclusions

• Versatility of Ketone: Ketone is a widely found and versatile organic function, used in a variety of industrial and biological contexts.

• Identification and Nomenclature of Ketone: Correct identification of a ketone is crucial for IUPAC and common nomenclature, which in turn influences the nomenclature of compounds derived from the ketone and the reactions it can undergo.

• Connected Organic Functions: The study of ketone represents an essential step in the broader understanding of the logic and reactivity of organic functions in general, providing a bridge between hydrocarbons and other functions such as alcohols, carboxylic acids, and ethers.

Exercises

1. Identify the chemical function and the IUPAC nomenclature of the following molecule: CH3CH2COCH3.

2. Classify the following ketones as primary, secondary, or tertiary: 2-pentanone, propanone, 3-methyl-2-butanone.

3. Write the structural formula and IUPAC nomenclature of a secondary ketone with five carbon atoms.