Contextualization

Theoretical Introduction

Organic chemistry is a branch of chemistry responsible for studying carbon compounds. August Kekulé, a German chemist, was one of the pioneers who made significant contributions to the advancement of this field. While studying the structure of benzene, Kekulé postulated two key ideas: the tetravalency of carbon (four valences of the carbon atom) and the formation of carbon chains.

The tetravalency of carbon means that a carbon atom can bond with up to four other atoms, filling its valence shell to achieve a stable configuration. This unique property allows for the formation of a wide variety of compounds, making carbon the foundation of all organic chemistry.

Kekulé's postulates also establish that carbon atoms have the ability to bind to each other, forming chains that are linear, branched, or cyclic structures. These chains can be saturated or unsaturated, depending on the presence or absence of double or triple bonds between the carbon atoms.

Contextualization

Verifying the application of Kekulé's postulates in the real world is essential. All organic compounds, from the simplest ones like methane to complex molecules present in medicines, pigments, cleaning products, plastics, and many others, are based on the rules established by Kekulé.

Thus, understanding Kekulé's postulates is fundamental for anyone who wishes to deepen their knowledge in chemistry, biochemistry, or chemical engineering. Moreover, by understanding these postulates, it is possible to better understand how organic compounds are formed and improve the understanding of the structure and function of these molecules in our lives and in the environment.

Reliable resources:

1. Organic Chemistry - Khan Academy
2. ORGANIC CHEMISTRY I - Tetravalent Carbon Theory and Kekule Postulates - YouTube
3. Organic Chemistry: Introduction - Brazil School
4. Book: "Organic Chemistry - Structure and Function" – K. Peter C. Vollhardt, Neil E. Schore.

Practical Activity

Activity Title: Applying Kekulé's Postulates

Project Objective

In this activity, students will apply Kekulé's postulates to create models of organic molecules. The goal is to understand the principles of carbon tetravalency and the formation of carbon chains.

Detailed Project Description

Groups of 3 to 5 students will select three different organic compounds and create physical models of these compounds using simple materials such as modeling clay and toothpicks. Each model should take into account the tetravalency of carbon and the formation of carbon chains.

In addition to the models, students will prepare a theoretical presentation to explain the structure of each chosen compound, basing their choices on Kekulé's postulates and demonstrating how these concepts apply in the real world.

Required materials

• Modeling clay in different colors
• Toothpicks
• Presentation slides

Detailed step-by-step instructions for carrying out the activity

1. Each group will select three different organic compounds. They can be simple, such as methane or ethane, or more complex.
2. Each group will research the molecular structure of their chosen compounds.
3. Each group will build physical models of their compounds using modeling clay and toothpicks. Carbon should be represented by one color and the other atoms by different colors. The toothpicks will represent the chemical bonds.
4. Each group will prepare a slide presentation explaining the structure of each of the chosen compounds, how Kekulé's postulates apply to the compounds, and where these compounds are found or used in the real world.
5. Each group will present their research and models to the class.

Project Deliverables

At the end of the project, each group will have created three models of organic compounds and a presentation explaining how Kekulé's postulates apply to these compounds.

In addition, each group will write a paper addressing the following points:

1. Introduction: Contextualization of Kekulé's postulates and their application in the real world. Presentation of the chosen compounds and the project's objective.
2. Development: Detailed discussion on how the tetravalency of carbon and the formation of carbon chains apply to the selected compounds. Detailed explanation of the methodology used to build the models and prepare the presentation. Presentation and discussion of the results obtained.
3. Conclusion: Return to the main points, discussion of lessons learned, and conclusions drawn about Kekulé's postulates from the project.
4. Bibliography: References used for the research and preparation of the project.