4.1 Acids and Bases
LEARNING GOALS
After Chapter 4.1, you will be able to:
Recall the importance of amphoteric species and common amphoteric molecules
Describe the meaning of pKa and pKb values in relation to acid and base strength
Recall common functional groups that act as acids or bases
In an acid–base reaction, an acid and a base react, resulting in the formation of the conjugate base
of the acid and the conjugate acid of the base. This reaction proceeds so long as the reactants are
more reactive, or stronger, than the products that they form. We will discuss acid and base
definitions and strength in the following section. For the MCAT, we will concern ourselves with the
broader Lewis and Brønsted–Lowry definitions of acids and bases. The Lewis definition concerns
itself with the transfer of electrons in the formation of coordinate covalent bonds; the Brønsted–
Lowry definition focuses on proton transfer.
KEY CONCEPT
An acid–base reaction will only proceed if the products that will be formed (the conjugate
base of the acid and the conjugate acid of the base) are weaker than the original reactants.
DEFINITIONS
A Lewis acid is defined as an electron acceptor in the formation of a covalent bond. Lewis acids
also tend to be electrophiles, which we will touch on in the next section. Lewis acids have vacant p-