Substrate

Definition

In the context of organic chemistry, a substrate is the molecule or compound that undergoes a chemical reaction, typically catalyzed by an enzyme or a reagent in a laboratory setting. Substrates serve as the starting material for various types of reactions, including biological reactions and laboratory reactions.

5 Must Know Facts For Your Next Test

1. Substrates are the molecules that bind to the active site of an enzyme, allowing the enzyme to catalyze a specific reaction.
2. In nucleophilic substitution reactions, the substrate is the molecule that contains the carbon-halogen bond that is targeted for substitution.
3. Elimination reactions, such as those governed by Zaitsev's rule, involve the removal of a small molecule (often water) from a substrate, resulting in the formation of a new carbon-carbon double bond.
4. Acidic cleavage of ethers involves the use of a proton source to break the ether bond, converting the ether substrate into two alcohol products.
5. Enzymes recognize and bind to specific substrates, allowing them to catalyze the desired transformation in biological systems.

Review Questions

• Explain the role of the substrate in biological reactions catalyzed by enzymes.
  • In biological reactions, the substrate is the molecule that binds to the active site of an enzyme. The enzyme recognizes the specific substrate and lowers the activation energy required for the reaction to occur, allowing it to proceed more quickly. The substrate undergoes a transformation catalyzed by the enzyme, which then releases the product(s) of the reaction. The specificity of the enzyme-substrate interaction is crucial for the efficient and selective nature of biological catalysis.
• Describe how the substrate is involved in nucleophilic substitution reactions.
  • In nucleophilic substitution reactions, the substrate is the molecule that contains the carbon-halogen bond that is targeted for substitution. The nucleophile attacks the carbon atom of the substrate, displacing the halogen atom and forming a new bond. The nature of the substrate, including the identity of the halogen and the surrounding functional groups, can influence the mechanism and stereochemical outcome of the substitution reaction.
• Analyze the role of the substrate in elimination reactions governed by Zaitsev's rule.
  • Elimination reactions, such as those described by Zaitsev's rule, involve the removal of a small molecule (often water) from a substrate, resulting in the formation of a new carbon-carbon double bond. The substrate in these reactions typically contains a leaving group (e.g., a halogen or a hydroxyl group) and an adjacent hydrogen atom. The substrate's structure and the relative stability of the possible alkene products dictate the outcome of the elimination reaction, as Zaitsev's rule states that the more substituted alkene is the predominant product.

Related terms

Enzyme: A biological catalyst that accelerates chemical reactions by lowering the activation energy required, without being consumed in the process.

Catalyst: A substance that increases the rate of a chemical reaction without being consumed or altered itself.

Reactant: The starting materials in a chemical reaction that are transformed into products.