My Problems

Published

List of user's published problems.

Problem # 612
 

Draw a mechanism for the nucleophilic aromatic substitution (SNAr) reaction below. Show all resonance forms of the intermediate.

Problem # 611

Draw in the arrows to show the electron flow and resonance forms in the nucleophilic aromatic substitution reaction below.

Note: Depending on the textbook, nucleophilic aromatic substitution is referred to as NAS, SNAr, or addition-elimination.

 

Problem # 596

Indicate the eletrophile formed by each set of reagents/conditions below.

Problem # 595
 

Phenol can be prepared from benzene and hydrogen peroxide in the presence of a really strong acid. Propose a mechanism for this reaction.

Problem # 594
 

A chemist tried to prepare compound A from benzene via Friedel-Crafts alkylation and instead produced compound B.

Why did this happen? How could the chemist prepare compound A?

Problem # 593

a) Rationalize the relative stabilities of the cation species below.

 

b) Pyridine undergoes eletrophilic substitution at C-3. Let's compare the resonance forms of EAS carbocation intermediates to see why this is the case. Consider part a) in your explanation.

Problem # 592

Naphthalene undergoes eletrophilic substitution at C-1.

Why is this the case, even though substitution at C-2 gives more resonance forms?

Problem # 591

Pyrrole undergoes eletrophilic aromatic substitution at C-2. Let's compare the resonance forms of EAS carbocation intermediates to see why this is the case. What do you think? Why C-2 and not C-3?

Problem # 590

-NO2 is an EWG and a meta director. Let's draw an EAS reaction's cyclohexadienyl cation intermediates to demonstrate why this is true. I've started you off.

What's good about meta? What's bad about ortho/para?

Problem # 589

 -OR is an EDG and an ortho-para director. Let's draw an EAS reaction's cyclohexadienyl cation intermediates to demonstrate why this is true. I've started you off.

What's good about ortho/para? What's bad about meta?

Problem # 588

Let's draw resonance forms to see why some groups are EDG or EWG. (I've started you off)

Where are the positive or negative charges placed in EDG/EWG? (ortho/meta/para) Why would this affect EAS reactions?

Note: EDG = electron donating group, EWG = electron withdrawing group

Problem # 587

Use curved arrows to draw a mechanism for the generic electrophilic aromatic substitution (EAS) reaction below.

Problem # 584

Imidazole (shown below) has two nitrogen atoms, N-1 and N-3. Which nitrogen is more basic?

To answer this problem, draw the product after each nitrogen protonates, and compare their stabilities. Explain your reasoning.

Problem # 583

Pyrrole is an example of a heteroaromatic compound: it contains a heteroatom (atom that is not carbon or hydrogen, such as N, O, S, etc.), and is aromatic.

Because pyrrole is aromatic, we should be able to draw many resonance forms- usually as many resonance forms as sides (in this case, five sides, so five resonane forms).

Draw all resonance forms for pyrrole. (I've started you off.)

Problem # 582
 

Rationalize the follwing pKa values. Explain your answer in terms of the stabilites of the conjugates bases of each acid.

Note: the lower the pKa, the stronger the acid.