3. Acids and Bases

Acetic acid can also react as a very weak base (pK_b = 20). Two different sites on acetic acid might become protonated to give the conjugate acid. Draw both of these possible conjugate acids, and explain (resonance) why the correct one is more stable. Calculate the pK_a of this conjugate acid.

Given the data in Problem 47:

b. What pH would you make the water layer to cause the carboxylic acid to dissolve in the water layer and the amine to dissolve in the ether layer?

Butyric acid, the compound responsible for the unpleasant odor and taste of sour milk, has a pK_a value of 4.82. What is its Ka value? Is it a stronger acid or a weaker acid than vitamin C?

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

(d)

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)