Substrate and Reagent
In organic chemistry, substrates are defined as the organic molecules that undergo chemical transformations during reactions. They contain the necessary carbon atoms involved in the formation of new bonds. Conversely, reagents are the substances that interact with the substrates to facilitate these transformations, enabling the conversion of reactants into products.
The definition of substrates can vary based on perspective. For instance, when reacting with other substances, the market chosen as a substrate depends on the focus of the study (e.g., the carbon chain undergoing reaction). In reactions like the addition of bromine to ethylene:
CH₂=CH₂ + Br₂ → CH₂Br-CH₂Br
Here, ethylene (CH₂=CH₂) acts as the substrate while bromine (Br₂) is the reagent.
The section also highlights nucleophiles and electrophiles. Nucleophiles are electron-rich species that seek electron-deficient sites (electrophiles). Conversely, electrophiles are electron-deficient, meaning they are electron-seeking and often contain polar bonds, making them available for nucleophilic attacks. For example:
- A hydroxide ion (OH⁻) acts as a nucleophile, attacking the positively charged carbon in a carbocation.
- A carbocation (like CH₃⁺) serves as an electrophile, ready to react with nucleophiles.
This interaction is pivotal to understanding mechanisms in organic chemistry. The movement of electrons during these reactions involves various notation techniques, predominantly the use of curved arrows to depict electron flow. By comprehension of the distinctions between substrates and reagents, and their roles as nucleophiles and electrophiles, students build a robust foundation for advancing in organic reaction mechanisms.