Q6P - Organic Chemistry (Mcmurry)

Question

Which would you expect to be a stronger acid, the lactic acid found in tired muscles or acetic acid? Explain.

Step-by-Step Solution

Answer

The lactic acid found in tired muscles is a stronger due to the inductive effect of a hydroxyl group.

Step1: Draw the structures of both acetic acid and lactic acid.

The structure of the lactic acid is drawn as follows:

Similarly, the structure of the acetic acid is drawn as follows:

Step 2: Find the stronger acid.

The lactic acid present in tired muscles is a stronger than the acetic acid. Because the hydroxyl ($\mathbf{-}\mathit{O}\mathit{H}$) group present at the second carbon of lactic acid stabilizes lactate anion (a conjugate base) through the inductive effect as shown below. 

The lactate anion is more stable than the acetate anion because more is the stability of anion, more will be the dissociation of acid into the solution.

Hence, the lactic acid is considered as a strong acid.