3. Acids and Bases

Each of these compounds can react as an electrophile. In each case, use curved arrows to show how the electrophile would react with the strong nucleophile sodium ethoxide, Na^{+ −}OCH₂CH₃.

a.

b. NH₄⁺

Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.

a.

In each case, circle the stronger nucleophile.

(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.

(b)

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.

Identify the arrow types that are shown in each of these arrow-pushing mechanisms.

(iii)

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)

Use curved arrows to show the movement of electrons in the following reaction steps

a.

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.

a.

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.

(a)

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)

Each of these compounds can react as an electrophile. In each case, use curved arrows to show how the electrophile would react with the strong nucleophile sodium ethoxide, Na^{+ −}OCH₂CH₃.

(c) CH₃CH₂Br

(d) BH₃

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

Using curved arrows, show the mechanism of the following reaction:

Predict the product that results from the following 'pushed electrons.'

(a)