Electrophilic Aromatic Substitution Practice Problems

Arrange the following compounds in ascending order of electrophilic aromatic substitution reactivity.

Consider the electrophilic aromatic substitution reaction: 

Predict its product.

I. What are the products of the electrophilic aromatic substitution reaction of benzene and the given epoxide in the presence of a Lewis acid such as AlCl₃?

II. Do you think aziridines will react similarly?

A highly colored compound is formed from the reaction of pyrrole and excess activated ketone. Draw the structure of the compound.

Draw a suitable mechanism for the reaction given below.

Determine if each substituent listed below is an ortho/para– or meta–director.
i) –CHO
ii) –CH₂CH₃
iii)  –O(C=O)CH₃

Draw the resonance structure(s) that show(s) why the carbonyl group is not an ortho/para–director.

For each compound, indicate the benzene carbon where bromine is added during the electrophilic aromatic bromination.

State whether the given statements are true or false.

I. To synthesize p-dimethylbenzene, a coupling reaction must be used.
II. p-Dimethylbenzene can be synthesized using a coupling reaction.

Draw the monochlorinated product(s) from the reaction of the compound below with one equivalent of Cl₂ in the presence of FeCl₃.

Determine the product of the reaction shown below:

Arrange the compounds below in decreasing order of reactivity toward the electrophilic aromatic substitution.

Adding substituents to a benzene ring affects its reactivity in various ways. Classify the given substituents in the following ways (choose one for each part):

Substituents: –OCH₃, –SO₃H, –C(CH₃)₃, –Cl

i) Electron-withdrawing group or electron-donating group?

ii) Participates in induction, resonance, or hyperconjugation?

iii) Ortho/para or meta director?

Draw the resonance contributors of phenoxide and phenol and explain why phenoxide is more reactive than phenol toward EAS.

Determine the major product of the reaction given below.

The Ritter reaction occurs when nitrile and alcohol react in the presence of an acid to form N-substituted amide. Provide an appropriate mechanism for the Ritter reaction depicted below.

The Ritter reaction occurs when nitrile and secondary or tertiary alcohol reacts in the presence of an acid to form N-substituted amide. Explain why the Ritter reaction does not work with primary alcohols.

The reaction of a nitrile with a secondary or tertiary alcohol to produce an N-substituted amide in the presence of an acid is called the Ritter reaction. The reaction includes the nucleophilic addition of a nitrile to a carbenium ion. What is the key difference between the Ritter reaction and the amide formation through acid-catalyzed hydrolysis of a nitrile? 

When three equivalents of bromine are added to 3,5-dimethylphenol in CCl₄, a product with the molecular formula C₈H₇Br₃O is obtained. This product is further treated with bromine water which results in another product with the molecular formula C₈H₆Br₄O. The IR spectrum of the second product shows a strong absorption at around 1685 cm^–1 (similar to that of quinone). Determine the structures of the two products.

Describe how 4-methylstyrene can be synthesized using toluene as the starting material.

tert-Butylhydroquinone (TBHQ) is a synthetic antioxidant commonly used as a preservative in edible oils. Devise an approach for its synthesis from hydroquinone.

Thymolphthalein is an acid-base indicator that is colorless below pH 9.3 and blue above pH 10.5. The synthesis of thymolphthalein involves the reaction of pthalic anhydride with two equivalents of thymol (2-isopropyl-5-methylphenol) in an acidic medium.

Write a mechanism for the reaction.

What major product is expected from the coupling reaction shown below?

What major product is expected from the coupling reaction shown below?

Which position is the most susceptible to an electrophilic attack on the following benzene derivatives?

What is the major product when the compound shown below reacts with Cl₂ and AlCl₃?

What is the major product when the compound shown below reacts with Cl₂ and AlCl₃?

What is the major product when the compound shown below reacts with Cl₂ and AlCl₃?

Identify the major product formed in the reaction between toluene and fuming sulfuric acid.

Write the product formed in the reaction given below

Write the product formed in the reaction given below

Write the product formed in the reaction given below

Determine the final major product formed in the reaction sequence given below:

Determine the final major product formed in the reaction sequence given below:

a. Show the structures of three isomers of dimethyl benzoate.

b. The nitration of the isomers at all possible positions was once used to determine their structures. The nitration of isomer A produced three mononitro isomers, isomer B produced two mononitro isomers while isomer C produced only one mononitro isomer. Label which of the isomer you drew is isomer A, which one is isomer B, and which one is isomer C.

Electrophilic aromatic substitution reactions are much faster with prop-1-en-1-ylbenzene compared to benzene. Explain this enhanced reactivity of prop-1-en-1-ylbenzene.

Draw the mechanism for the ortho and para bromination of methoxybenzene.

Show how this compound can be synthesized using benzene or any other required reagents.

The synthesis of the following compound may require the use of a Pd-catalyzed coupling reaction as the final step.

What major product is expected from the coupling reaction shown below?

Describe how a Suzuki coupling reaction can be used to synthesize the compound shown below:

As starting material, you can use 1-bromo-2-isopropylbenzene and any other required reagents.

The electrophilic aromatic substitution reaction rate for indole is 10¹³ times greater than that of benzene. It often reacts under mild reaction conditions. Substitution in indole occurs preferably at position 3.

Propose a mechanism for the bromination of indole. You do not have to show steps for generating the Br⁺ ion. You may begin with indole and Br⁺ ion. Draw resonance forms for each sigma complex.

The electrophilic aromatic substitution reaction rate for indole is 10¹³ times greater than that of benzene. It often reacts under mild reaction conditions. Substitution in indole occurs preferably at position 3.

Explain why indole is more reactive than benzene and why substitution preferably takes place at position 3 than position 2.

Biphenyl is an aromatic compound having two benzene rings joined by a single bond. The site of an electrophilic aromatic reaction is usually the one that is on the more activated ring. The other ring and other substituents (if present) also affect the reaction regiochemistry.
For the following reaction, use resonance forms of a sigma complex to explain the observed regiochemistry.

Biphenyl is an aromatic compound having two benzene rings joined by a single bond. The site of an electrophilic aromatic reaction is usually the one that is on the more activated ring. The other ring and other substituents (if present) also affect the reaction regiochemistry.

Predict the major product of a monochlorination reaction for the following compound:

Biphenyl is an aromatic compound having two benzene rings joined by a single bond. The site of an electrophilic aromatic reaction is usually the one that is on the more activated ring. The other ring and other substituents (if present) also affect the reaction regiochemistry.

Predict the major product of a monochlorination reaction for the following compound:

Biphenyl is an aromatic compound having two benzene rings joined by a single bond. The site of an electrophilic aromatic reaction is usually the one that is on the more activated ring. The other ring and other substituents (if present) also affect the reaction regiochemistry.

Predict the major product of a monochlorination reaction for the following compound:

Iodination of ethylbenzene follows electrophilic aromatic substitution. In the second step of this reaction, water acts as a base and removes a proton from the sigma complex. Show the product you would expect if the water would act as a nucleophile instead of a base. Explain why this reaction is not feasible.

Show how the following conversion can be achieved with good yield. Use any necessary reagents.

Suggest a plausible mechanism for the following reaction. Explain briefly why sulfonation takes place at carbon number 3 of 4-methylpyridine.

The electrophilic aromatic substitution reaction rate for thiophene is greater than that of benzene. It often reacts under mild reaction conditions. Substitution in thiophene occurs preferably at position 2.

Draw a mechanism for the acetylation of thiophene. You do not have to show steps for generating the CH₃C≡O⁺ ion. You may begin with thiophene and CH₃C≡O⁺ ion.

The electrophilic aromatic substitution reaction rate for thiophene is greater than that of benzene. It often reacts under mild reaction conditions. Substitution in thiophene occurs preferably at position 2.

Explain why thiophene is more reactive than benzene and why substitution preferably takes place at position 2 than position 3.

Write a synthetic sequence to convert aniline to the following compound:

Use any reagents necessary to carry out the transformation.

Consider the reaction of the benzene derivatives below via electrophilic aromatic substitution. Identify which compound is expected to react most quickly and which would react most slowly.

The ketone group is a meta-director for EAS reactions. If the ketone group undergoes hydrogenation, to which position does the hydrogenation product direct EAS?