Chapter 4, Problem 28E

The following are equivalent ways of asking about the acidity of an H atom:
• What is the most acidic H on the molecule?
• Which H is associated with the published $\text{p}{K}_a$ value?
• Which H on the molecule is easiest to remove?
• Which H on the molecule takes the least energy to remove?
• Which bond to an H is most polarized?
• For which H atom is removal least uphill in energy?
• Which bond to an H atom, when broken, results in the lowest PE conjugate base?
We will often find the last of these questions is easiest to answer. To do this, find all the different Hatoms on the molecule, and draw all possible conjugate bases.Only the lowest-energy one is the “real” conjugate base. Identify this structure, and you have found the most acidic H.
Use this strategy to find the most acidic H on each of the following molecules. Note: Each structure hasat least three different kinds of H’s, so draw at least three unique conjugate bases for each.