Introduction

Acids and Bases. For those of you who have taken general chemistry, you might be thinking, “Yuck” or “Uh-oh”. There are many chemical definitions for acids and bases. That’s confusing. We use mathematical terms like negative log. That’s confusing because when we first learned about logs in junior high or early high school math, we did not believe our teachers when they told us it was important. And, then there is the small “p” (pH, pKa, pKb) and logarithms.

So, at the start of this chapter, I need to reassure you that the way organic chemists usually talk about acids and bases is much simpler than what you learned in general chemistry. Don’t be intimidated. Give me a chance to explain this before you turn off your mind. Also, let me assure you that all of those terms in the previous paragraph become much less confusing and much more understandable as you continue your chemistry education. It is something you need to look at several times before it “clicks”. That’s like a lot of things in life that are worth knowing and doing.

The definitions of acids and bases that are typically taught in general chemistry are the Arrhenius, Brønsted-Lowry, and Lewis definitions. Believe it or not, there are even more ways to define acids and bases. In organic chemistry, when one speaks of an acid or base, they are most likely speaking of the Brønsted-Lowry definition. The Arrhenius definition is too simple. You might hear an organic chemist use the terms Lewis acid or base, instead they usually will use the terms electrophile or nucleophile, respectively.

The Brønsted-Lowry acid is a proton (H+) donor. A Brønsted-Lowry base is a proton (H+) acceptor.