Chemistry Reference
In-Depth Information
Scheme 2.1 General representation of acid dissociation.
Figure 2.1 Solvent effects on acid dissociation.
than to how electrons move. Therefore, solvent polarity will not be addressed further in this
chapter and will be revisited in the context of various mechanistic types.
In addition to external factors such as solvent effects, there are internal factors that
influence anionic stability. Among these are inductive effects (how do electron-donating
or electron-withdrawing substituents affect a molecule?), and resonance effects (is
the charge localized or delocalized?). As inductive effects generally work in concert
with resonance effects, our primary focus will be on the resonance effects themselves.
2.2 WHAT IS RESONANCE?
When a given molecule or ion can exist with multiple configurations of double
/
triple bonds
or multiple sites bearing positive
/
negative charges, the molecule or ion is said to possess
resonance forms. These resonance forms can be represented by drawings where the
changes in electronic configuration are rationalized using arrow pushing. Furthermore,
these changes in electronic configuration occur with no alterations to the connectivity of
the individual atoms. For example, as shown in Scheme 2.2, a carboxylic acid dissociates
into a proton and a carboxylate anion. As shown in Scheme 2.3, this carboxylate anion
possesses two resonance structures. These resonance structures,
illustrated using a
