3. Acids and Bases

Provide a reasonable arrow-pushing mechanism for the following Lewis acid–Lewis base reactions.

(a)

Provide an arrow-pushing mechanism for the following hypothetical base half-reactions.

(b)

BCl₃ has an empty p orbital, so it is a strong Lewis acid. Would you expect an amide to react with BCl₃ at nitrogen or oxygen?

In each case, circle the stronger nucleophile.

(b)

Based on the analysis you used in Assessment 17.3, which carbonyl would you expect to react most quickly with a nucleophile?

(c)

Classify the following nucleophiles as strong, weak, or intermediate. Would you expect each to add to a carbonyl directly or wait for a carbocation to form?

b)

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.