3. Acids and Bases

Four pairs of compounds are shown. In each pair, one of the compounds reacts more quickly, or with a more favorable equilibrium constant, than the less conjugated system. In each case, explain the enhanced reactivity.

(d)

Use resonance forms of the conjugate bases to explain why methanesulfonic acid (CH₃SO₃H, pK_a = –2.6) is a much stronger acid than acetic acid (CH₃COOH, pK_a = 4.8).

Acetylacetone (pentane-2,4-dione) reacts with sodium hydroxide to give water and the sodium salt of a carbanion. Write a complete structural formula for the carbanion, and use resonance forms to show the stabilization of the carbanion.

Identify the stronger base in each pair. Explain your choice. Citing pK_a values is not an acceptable answer.

(a)

Identify the stronger base in each pair. Explain your choice. Citing pK_a values is not an acceptable answer.

(c)

Identify the stronger acid in each pair. Explain your choice. Citing pK_a values is not an acceptable answer.

(a)

Without using pK_a values, pick out the least reactive (most stable) base in each pair. Explain your answer.

(a)

Without using pK_a values, pick out the least reactive (most stable) base in each pair. Explain your answer.

(c)

Which of the following indicated atoms would you expect to be most basic?

(a)

Without using pK_a values, pick out the more acidic compound in each pair. Explain your answer.

(a)

Without using pK_a values, pick out the more reactive (least stable) base in each pair. Explain your answer.

(a)

Tenormin, a member of the group of drugs known as beta-blockers, is used to treat high blood pressure and improve survival after a heart attack. It works by slowing down the heart to reduce its workload. Which atom in Tenormin is the most basic?

A carboxylic acid ( pK_a = 5) is 10¹¹ times more acidic than an alcohol (pK_a = 16). Why?

Compare the properties of propan-2-ol (I) and the hexafluoro analog (II).

(a) Compound II has almost triple the molecular weight of I, but II has a lower boiling point. Explain.

e. Which has a greater Ka: cyclohexanol or phenol?

f. Which is a stronger acid: cyclohexanol or phenol?