For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.

c.

d.

Fosamax (shown on the previous page) has six acidic groups. The active form of the drug, which has lost two of its acidic protons, is shown in the box. 

(Notice that the phosphorus atom in Fosamax and the sulfur atom in [Problem 36] can be surrounded by more than eight electrons because P and S are below the second row of the periodic table.)

a. Why are the OH groups bonded to phosphorus the strongest acids of the six groups?

b. Which of the remaining four groups is the weakest acid?

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?

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

d. Which is more electronegative: an sp³ oxygen or an sp² oxygen?

e. Which compounds demonstrate that the relative electronegativities of a hybridized nitrogen atom are sp > sp² > sp³?

For each of the following compounds (here shown in their acidic forms), write the form that ­predominates in a solution with a pH = 5.5:

a. CH₃COOH(pK_a = 4.76)

b. CH₃CH₂N⁺H₃ (pK_a = 11.0)

For each of the following compounds (here shown in their acidic forms), write the form that ­predominates in a solution with a pH = 5.5:

c. H₃O⁺ (pK_a = −1.7)

d. HBr (pK_a = −9)

For each of the following compounds (here shown in their acidic forms), write the form that ­predominates in a solution with a pH = 5.5:

e. ⁺NH4 (pK_a = 9.4)

f. HC≡N (pK_a = 9.1)

For each of the following compounds (here shown in their acidic forms), write the form that ­predominates in a solution with a pH = 5.5:

g. HNO₂ (pK_a = 3.4)

h. HNO₃ (pK_a = −1.3)

For each of the following compounds (here shown in their acidic forms), write the form that ­predominates in a solution with a pH = 5.5:

i. HON⁺H₃ (pK_a = 6.0)

As long as the pH is not less than ___________, at least 50% of a protonated amine with a pK_a value of 10.4 will be in its neutral, nonprotonated form.

Indicate whether a protonated amine (RN⁺H₃) with a pKa value of 9 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

1. pH = 1

2. pH = 3

3. pH = 5

4. pH = 7

5. pH = 10

6. pH = 13

Indicate whether an alcohol (ROH) with a pK_a value of 15 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

1. pH = 1

2. pH = 3

3. pH = 5

Indicate whether an alcohol (ROH) with a pK_a value of 15 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

3. pH = 7

4. pH = 10

5. pH = 13

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pK_a values of the two groups are shown.

c. Draw the structure of alanine in a solution at physiological pH (pH 7.4).

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pK_a values of the two groups are shown.

d. Draw the structure of alanine in a solution at pH = 12.

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pK_a values of the two groups are shown.

e. Is there a pH at which alanine is uncharged (that is, neither group has a charge)?

f. At what pH does alanine have no net charge (that is, the amount of negative charge is the same as the amount of positive charge)?

At what pH is the concentration of a compound, with a pK_a = 8.4, 100 times greater in its acidic form than in its basic form? At what pH is 50% of a compound, with a pK_a = 7.3, in its basic form?

At what pH is the concentration of a compound, with a pK_a = 4.6, 10 times greater in its basic form than in its acidic form?

For each of the following compounds, indicate the pH at which

a. 50% of the compound is in a form that possesses a charge.

1. CH₃CH₂COOH (pK_a = 4.9)

2. CH₃N⁺H₃ (pK_a = 10.7)

For each of the following compounds, indicate the pH at which

b. more than 99% of the compound is in a form that possesses a charge.

    1. CH₃CH₂COOH (pK_a = 4.9)

    2. CH₃N⁺H₃ (pK_a = 10.7)

Given the data in Problem 47:

a. 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?

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?

Write the equation that shows how a buffer made by dissolving CH₃COOH and CH₃COO⁻Na⁺ in water prevents the pH of a solution from changing appreciably when

a. a small amount of H⁺ is added to the solution.

b. a small amount of HO⁻ is added to the solution.

Draw the products of the following reactions. Use curved arrows to show where the pair of electrons starts and where it ends up.

a.

b.

What products are formed when each of the following reacts with HO⁻?

a. CH₃OH

b. ⁺NH₄

What products are formed when each of the following reacts with HO⁻ ?

c. CH₃N⁺H₃

d. BF₃

What products are formed when each of the following reacts with HO⁻ ?

e. ⁺CH₃

f. FeBr₃

Explain the relative acidities.

b. How does the presence of an electronegative substituent such as Cl affect the acidity of a carboxylic acid?

c. How does the location of the substituent affect the acidity of the carboxylic acid?

Draw the products of the following reactions:

a.

b.

c.