3. Acids and Bases

Would you expect a ketone or an ester to be more reactive with a strong nucleophile? Justify your answer.

Rank the reactivity of the following carbonyls with nucleophiles, from least reactive to most reactive.

The following reaction steps are shown using conventional electron pushing. (a) Draw the second product whose formation would have been rationalized with this same arrow.

(a)

The following reaction steps are shown using conventional electron pushing. (b) Use the bouncing arrow formalism to illustrate the formation of only the product shown.

(a)

For the following acid–base pairs, (v) show a mechanism for the reaction;

(e)

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

a.

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

b.

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

c.

Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions.

i.

In each reaction, label the reactants as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions. Draw any nonbonding electrons to show how they participate in the reactions.

c.

Each of these compounds can react as a nucleophile. In each case, use curved arrows to show how the nucleophile would react with the strong electrophile BF₃.

(e) CH₃CH₂OH

Each of these compounds can react as a nucleophile. In each case, use curved arrows to show how the nucleophile would react with the strong electrophile BF₃.

(f) (CH₃)₂S

Which atoms in the enol ether would you expect to react with Br⁺ ?

To which atom of formaldehyde would you expect H⁺ to add?

For practice in recognizing mechanisms, classify each reaction according to the type of mechanism you expect:

1. Free-radical chain reaction

2. Reaction involving strong bases and strong nucleophiles

3. Reaction involving strong acids and strong electrophiles

(b)