3. Acids and Bases

For the bases shown, draw the conjugate acid and identify a pK_a value from Table 4.5 that would help you accurately estimate its stability.

(b)

For the bases shown, draw the conjugate acid and identify a pK_a value from Table 4.5 that would help you accurately estimate its stability.

(e)

Hydrogen gas (H₂) has a relatively high pK_a value. Is it a stable or unstable acid? Do you expect it to participate in acid–base reactions?

Arrange each group of compounds in order of increasing basicity.

c. sodium benzoate, sodium ethoxide, and sodium phenoxide

d. pyridine, sodium ethoxide, and sodium acetate

Hydrogen peroxide (HOOH) has a pK_a of 11.6, making it roughly 10,000 times as strong an acid as water (pK_a = 15.7). Explain why H₂O₂ is a stronger acid than H₂O.

Peroxyacetic acid (pK_a = 8.2) is a much weaker acid than acetic acid (pK_a = 4.74). Explain why peroxyacetic acid is a weaker acid than acetic acid.

Give the pK_a value of the following compounds.

b.

Using the table of pK_a values given in [Appendix I], answer the following:

a. Which is the most acidic organic compound in the table?

b. Which is the least acidic organic compound in the table?

c. Which is the most acidic carboxylic acid in the table?

For the bases shown, draw the conjugate acid and identify a pK_a value from Table 4.5 that would help you accurately estimate its stability.

(c)

For each indicated proton, suggest an approximate pK_a value from Table 4.5. Rationalize your choice.

(b)

For the bases shown, draw the conjugate acid and identify a pK_a value from Table 4.5 that would help you accurately estimate its stability.

(d)

a. Which is a stronger base: CH₃COO⁻ or HCOO⁻? (The pK_a of CH₃COOH is 4.8; the pK_a of HCOOH is 3.8.)

b. Which is a stronger base: HO⁻ or ^-NH₂? (The pK_a of H2O is 15.7; the pK_a of NH3 is 36.)

c. Which is a stronger base: H₂O or CH₃OH? (The pK_a of H3O+ is −1.7; the pK_a of CH₃O⁺H₂ is −2.5.)

A medicinal chemist needed to deprotonate acetylene ( HC≡CH ) for use in a coupling reaction. Among the options given, which base(s) could be used for this process?

For each compound, indicate the atom that is most apt to be protonated.

a.

b.

c.

Rank the following from strongest base to weakest base:

b.