Base

Definition

A base is a substance that can accept a proton (H+) from an acid, forming a conjugate acid-base pair. Bases are characterized by their ability to increase the pH of a solution, neutralize acids, and serve as nucleophiles in various chemical reactions.

5 Must Know Facts For Your Next Test

1. Bases can neutralize acids by accepting a proton, forming a salt and water as products.
2. The strength of a base is determined by its ability to accept protons, with stronger bases having a greater affinity for protons.
3. Bases can act as nucleophiles in organic reactions, attacking electrophilic carbon centers to form new bonds.
4. The Wolff-Kishner reduction is an example of a nucleophilic addition reaction involving a base (hydrazine) as the nucleophile.
5. The pH of a solution is a measure of the concentration of hydrogen ions (H+), with bases increasing the pH by decreasing the H+ concentration.

Review Questions

• Explain how the Brønsted-Lowry definition of acids and bases relates to the concept of a base.
  • According to the Brønsted-Lowry theory, a base is a substance that can accept a proton (H+) from an acid, forming a conjugate acid-base pair. This means that a base is a proton acceptor, and its ability to accept protons is what defines it as a base. The Brønsted-Lowry definition provides a more general understanding of acids and bases compared to the earlier Arrhenius theory, allowing for a wider range of substances to be classified as acids or bases.
• Describe the role of a base in the Wolff-Kishner reduction reaction.
  • In the Wolff-Kishner reduction, a base (typically hydrazine) acts as a nucleophile, attacking the carbonyl carbon of a ketone or aldehyde. This nucleophilic addition reaction results in the formation of a hydrazone intermediate, which is then further reduced to form an alkane. The base serves a crucial role in this reaction by facilitating the nucleophilic attack and subsequent steps that lead to the final product. The ability of the base to act as a nucleophile is a key feature that enables the Wolff-Kishner reduction to occur.
• Analyze how the pH of a solution is influenced by the presence of a base, and explain the significance of this relationship.
  • Bases are characterized by their ability to increase the pH of a solution by decreasing the concentration of hydrogen ions (H+). When a base is added to a solution, it accepts protons, lowering the H+ concentration and thereby increasing the pH. This pH-raising effect of bases is crucial in various chemical and biological processes, such as the neutralization of acids, the maintenance of homeostasis in the body, and the regulation of enzymatic reactions. Understanding the relationship between bases and pH is essential for predicting and controlling the acidity or basicity of solutions in organic chemistry and other fields of study.

Related terms

Brønsted-Lowry Acid-Base Theory: A theory that defines acids and bases in terms of proton donors and acceptors, respectively. It provides a more general definition than the earlier Arrhenius theory.

Nucleophile: A species that donates an electron pair to form a new covalent bond, often acting as a base in chemical reactions.

Conjugate Base: The species formed when a base accepts a proton, resulting in a weaker base.