Contextualization

Kekulé's Postulates establish the basis for our understanding of the structure of organic compounds, particularly those containing carbon. Friedrich August Kekulé was a German chemist who, in the 19th century, postulated that carbon is tetravalent, meaning it has the ability to form four chemical bonds. Additionally, he proposed that carbon molecules can join together to form long chains or rings, a concept that revolutionized the field of organic chemistry.

Understanding these postulates is fundamental to comprehend how organic compounds are formed and how they interact. In fact, Kekulé's theory enabled the exploration of numerous chemical compounds, contributing to various scientific and technological advances, from the development of new drugs to the creation of synthetic materials.

Here, we will outline a project that will address Kekulé's Postulates in a thorough and applied manner, involving students in theoretical and practical activities that will allow them to understand and apply these concepts to real situations. Through this project, students will have the opportunity to investigate, experiment, and explain Kekulé's postulates, enhancing their understanding of the subject and their research and teamwork skills.

Organic chemistry has been a longstanding ally of technological advancement, being responsible for numerous breakthroughs that have revolutionized society. From the creation of new drugs, food production, development of materials and clean technologies, to even the impact on the environment. All of this goes through organic chemistry and, more specifically, through Kekulé's postulates.

Students are encouraged to consult the following resources to delve deeper into the topic and potentially use them as references in the project:

1. Khan Academy - Organic Chemistry - A free educational platform that provides a series of videos and exercises on organic chemistry.
2. YouTube - All Chemistry - Organic Chemistry - This playlist offers short videos covering various topics in organic chemistry, including Kekulé's Postulates.
3. Practical Study - Organic Chemistry - An educational website with a section dedicated to organic chemistry, which includes Kekulé's postulates.
4. Brazil School - Carbon Tetravalence Theory - An educational page that explains the theory of carbon tetravalence with clear examples.
5. Educational Video: Kekulé - The Dreamer of Carbon Chains - An animated video that tells the story of Friedrich August Kekulé and his discovery.

Practical Activity: Modeling Carbon Tetravalence

Project Objective

The proposed activity aims to strengthen students' understanding of the fundamentals of Kekulé's postulates theory, especially regarding carbon tetravalence and the formation of carbon chains. This will be achieved through the physical modeling of organic molecules and the discussion of these models in relation to theoretical concepts.

Activity Description

Students will be divided into groups of 3 to 5 people. Each group will have to choose two organic compounds (one open-chain and one closed-chain) to model using a molecular modeling kit. The groups should study in depth the structures of the selected compounds, identifying the types of bonds present and the different possible conformations of these molecules.

After creating the models, students will photograph and draw their structures, noting details such as the number and type of atoms, the number and type of bonds, and any other relevant characteristics. They should then present their models to the class, explaining their characteristics and how these relate to Kekulé's postulates.

Necessary Materials

• Molecular modeling kit
• Photography and/or drawing of the models
• Paper and pens to note the models' characteristics

Step by Step

1. Formation of groups.
2. Each group chooses two organic compounds to represent and studies their structures.
3. The groups build the models using the molecular modeling kit.
4. They photograph and/or draw the created models and note their characteristics.
5. Present their models to the class, explaining their characteristics and how these relate to Kekulé's postulates.

Deliverables

Students must present a written report documenting the entire project process, from the choice of organic compounds to the final presentation. The report should include the following:

1. Introduction: contextualization of the theme, the relevance and application of Kekulé's postulates in the real world, and the objective of this project.
2. Development: detailed explanation of Kekulé's postulates theory, description of the process of choosing organic compounds, description of the construction of the models, photos/drawings of the models, description of the noted characteristics, and a discussion of these in relation to Kekulé's postulates.
3. Conclusions: review of the main points of the work, reflection on the learning obtained, conclusions drawn from the project, and suggestions for future investigations.
4. Bibliography: citation of the sources used for the project.

Students must also present the models they built, along with photographs and/or drawings of them.