1. CH 3-3: Mechanism of Acid/Base Reactions
conj. base conj. acid
In organic chemistry the products of any reaction can usually be predicted if we understand the mechanism for that reaction.
The mechanism for a reaction consists of one, or a series of balanced equations (i.e., steps) where the movement of pairs of electrons are represented by curved arrows.

2. The Mechanism of Acid-Base Reactions
For the partial reaction below: -label the acid and base reactants; -use curved arrows to show electron pair movement; -draw the products; -label the conjugate acid and conjugate base;
-indicate if products or reactants are favored. ?
Base
Acid CA CB

3. Predicting the Equilibrium Direction of Acid-Base Reactions
Estimate the pKa of the acid reactant and CA product;
Equilibrium will favor the weaker acid…….WHY?
pKa ~ 16
Base
Acid
(more stable acid) CA CB
pKa ~ 9
(more reactive acid)

4. The Mechanism of Acid-Base Reactions
For the partial reaction on the next slide: -label the acid and base reactants; -use curved arrows to show electron pair movement; -draw the products; -label the conjugate acid and conjugate base; -label each acid species with its approx. pka -indicate if products or reactants are favored.

5. Example
Base ~5
Acid CA CB ~9