Introduction: Organic Reactions - Addition

Relevance of the Theme

Addition reactions in Organic Chemistry are crucial for understanding how covalent bonds are formed and broken. They open up a wide range of possibilities, allowing simple compounds to transform into extraordinarily complex compounds. It is through these reactions that we can, for example, extract dyes from flowers, prepare medicines, and produce polymers for a variety of applications.

Contextualization

The study of addition reactions fits into the discipline of Organic Chemistry, which is the chemistry of carbon compounds. This branch of chemistry is fundamental in understanding how life works, as organic compounds are the basis of living beings, including everything from carbohydrates and proteins to nucleic acids and lipids.

Addition is one of the main pathways for the formation and modification of these compounds. By the third year of high school, students have already had a general introduction to Organic Chemistry, including the structure and nomenclature of organic compounds, as well as the characteristics of covalent bonds.

This prior knowledge is essential for understanding addition reactions, which will expand this initial vision, showing how the manipulation of reaction conditions and the molecular structure of the reagents impact the final outcome of the reaction. This sets the stage for more advanced studies in Organic Chemistry at the undergraduate level, and also has immediate practical applications, for example, in understanding the effects of certain medicines and drugs, as well as in the production of synthetic materials in laboratories and industries.

Theoretical Development: Addition in Organic Reactions

Components

• Nature of Addition Reactions: In addition, two molecules or ions come together to form a single molecule. The structure of the resulting product is a combination of the atoms from both initial molecules and, therefore, has a higher molar mass.

• Types of Addition Reactions: There are several types of addition reactions, such as addition to alkenes and alkynes, addition of hydrogen halides to alkenes, addition of halogens to alkenes, addition of acids to alkynes, among others. Each type of addition reaction follows a particular mechanism, which involves the breaking and formation of bonds of different energies.

• Effect of Reaction Conditions on Addition: Reaction conditions, such as temperature, pressure, and catalysts, can significantly impact the outcome of an addition reaction. For example, under some circumstances, an addition reaction can be reversed, leading to the formation of the original reagents.

Key Terms

• Molecule: The smallest unit of a substance that retains its chemical characteristics. It is composed of two or more atoms joined by covalent bonds.

• Ion: An atom or group of atoms that has gained or lost electrons, thus acquiring an electric charge.

• Reaction Mechanism: The sequence of events that occurs in a chemical reaction, from the initial interaction between the reagents to the formation of the final products.

• Catalyst: A substance that increases the speed of a chemical reaction without being consumed in the process.

Examples and Cases

• Hydrogen Addition to Alkenes (hydrogenation): This is one of the most common and important addition reactions. It is used for the production of saturated fats from unsaturated oils and is also the basis for petroleum reforming.

• Halogens Addition to Alkenes (halogenation): In this reaction, a halogen (such as chlorine or bromine) is added to an alkene, resulting in the addition of a halogen atom to each end of the double bond.

• Hydrochloric Acid Addition to Alkynes (hydration): In this reaction, the hydrogen and halogen from an acid are added to the carbon atoms of the double bond, producing a compound that can be considered the result of adding a water molecule to the original double bond. This reaction is an important step in the production of carboxylic acids.