Podcast
Questions and Answers
Which of the following statements about electron withdrawing groups is true?
Which of the following statements about electron withdrawing groups is true?
What is the difference in reaction speed for electrophilic substitution of nitrobenzene compared to benzene?
What is the difference in reaction speed for electrophilic substitution of nitrobenzene compared to benzene?
Which product is predominantly formed during nitration of nitrobenzene?
Which product is predominantly formed during nitration of nitrobenzene?
How do halogens affect the reactivity of the benzene ring in electrophilic aromatic substitution?
How do halogens affect the reactivity of the benzene ring in electrophilic aromatic substitution?
Signup and view all the answers
Why is meta attack less unfavorable than ortho or para in some electrophilic aromatic substitution reactions?
Why is meta attack less unfavorable than ortho or para in some electrophilic aromatic substitution reactions?
Signup and view all the answers
What is the purpose of using acyl chloride in Friedel-Crafts acylation?
What is the purpose of using acyl chloride in Friedel-Crafts acylation?
Signup and view all the answers
What condition is necessary for the Clemmensen reduction?
What condition is necessary for the Clemmensen reduction?
Signup and view all the answers
Which catalysts can be used in the catalytic hydrogenation of benzene?
Which catalysts can be used in the catalytic hydrogenation of benzene?
Signup and view all the answers
What is the result of oxidizing the benzylic carbon position?
What is the result of oxidizing the benzylic carbon position?
Signup and view all the answers
What happens in the radical halogenation of the aromatic side chain?
What happens in the radical halogenation of the aromatic side chain?
Signup and view all the answers
What is a sigma complex in the context of electrophilic aromatic substitution?
What is a sigma complex in the context of electrophilic aromatic substitution?
Signup and view all the answers
How does the presence of an electron donating group (EDG) affect electrophilic aromatic substitution?
How does the presence of an electron donating group (EDG) affect electrophilic aromatic substitution?
Signup and view all the answers
Which of the following is an example of an electron withdrawing group (EWG)?
Which of the following is an example of an electron withdrawing group (EWG)?
Signup and view all the answers
When an aromatic ring is substituted, what factors determine the position of the second electrophile's attack?
When an aromatic ring is substituted, what factors determine the position of the second electrophile's attack?
Signup and view all the answers
What is the primary outcome of a nitration reaction on an aromatic compound?
What is the primary outcome of a nitration reaction on an aromatic compound?
Signup and view all the answers
Which positions on the aromatic ring are typically affected by -OH as an electron donating group?
Which positions on the aromatic ring are typically affected by -OH as an electron donating group?
Signup and view all the answers
What role do resonance effects play in the mechanism of electrophilic aromatic substitution?
What role do resonance effects play in the mechanism of electrophilic aromatic substitution?
Signup and view all the answers
Which of the following statements about deactivating substituents is true?
Which of the following statements about deactivating substituents is true?
Signup and view all the answers
Which groups are known to direct electrophilic aromatic substitution to the meta position?
Which groups are known to direct electrophilic aromatic substitution to the meta position?
Signup and view all the answers
What is a factor that stabilizes the intermediates for ortho and para products over meta products during electrophilic aromatic substitution?
What is a factor that stabilizes the intermediates for ortho and para products over meta products during electrophilic aromatic substitution?
Signup and view all the answers
Which compound is likely to have the highest reactivity toward electrophilic aromatic substitution?
Which compound is likely to have the highest reactivity toward electrophilic aromatic substitution?
Signup and view all the answers
What role does the methyl group in toluene play during electrophilic aromatic substitution reactions?
What role does the methyl group in toluene play during electrophilic aromatic substitution reactions?
Signup and view all the answers
Which of the following correctly ranks the compounds in order of decreasing reactivity toward electrophilic aromatic substitution?
Which of the following correctly ranks the compounds in order of decreasing reactivity toward electrophilic aromatic substitution?
Signup and view all the answers
Which of the following describes the directing effects of halogens in electrophilic aromatic substitution?
Which of the following describes the directing effects of halogens in electrophilic aromatic substitution?
Signup and view all the answers
In the resonance hybrid of the carbocation intermediates during electrophilic aromatic substitution, what contributes to stability in ortho/para intermediates?
In the resonance hybrid of the carbocation intermediates during electrophilic aromatic substitution, what contributes to stability in ortho/para intermediates?
Signup and view all the answers
Why are electron-donating groups important during electrophilic aromatic substitution?
Why are electron-donating groups important during electrophilic aromatic substitution?
Signup and view all the answers
What type of directing effect does a bromo substituent have in electrophilic aromatic substitution (EAS)?
What type of directing effect does a bromo substituent have in electrophilic aromatic substitution (EAS)?
Signup and view all the answers
What is the effect of a nitro substituent in EAS?
What is the effect of a nitro substituent in EAS?
Signup and view all the answers
What effect do alkyl groups have on the aromatic ring during electrophilic attack?
What effect do alkyl groups have on the aromatic ring during electrophilic attack?
Signup and view all the answers
Why are ortho and para attacks preferred over meta attacks in electrophilic aromatic substitution?
Why are ortho and para attacks preferred over meta attacks in electrophilic aromatic substitution?
Signup and view all the answers
In a situation where multiple substituents have opposing directing effects, which substituent's influence is most significant?
In a situation where multiple substituents have opposing directing effects, which substituent's influence is most significant?
Signup and view all the answers
What is a potential limitation of the Friedel-Crafts alkylation reaction?
What is a potential limitation of the Friedel-Crafts alkylation reaction?
Signup and view all the answers
How much faster does anisole undergo nitration compared to benzene?
How much faster does anisole undergo nitration compared to benzene?
Signup and view all the answers
What is the impact of electron-withdrawing groups on the aromatic ring?
What is the impact of electron-withdrawing groups on the aromatic ring?
Signup and view all the answers
What is the outcome when a highly deactivating group is present on a benzene ring during Friedel-Crafts alkylation?
What is the outcome when a highly deactivating group is present on a benzene ring during Friedel-Crafts alkylation?
Signup and view all the answers
What happens when an electrophile attacks the aromatic ring at positions ortho or para relative to an electron-withdrawing group?
What happens when an electrophile attacks the aromatic ring at positions ortho or para relative to an electron-withdrawing group?
Signup and view all the answers
Which alkyl halide is typically used in Friedel-Crafts alkylation to ensure the formation of a carbocation?
Which alkyl halide is typically used in Friedel-Crafts alkylation to ensure the formation of a carbocation?
Signup and view all the answers
Which of the following statements accurately describes the role of methoxy and amino groups in electrophilic aromatic substitution reactions?
Which of the following statements accurately describes the role of methoxy and amino groups in electrophilic aromatic substitution reactions?
Signup and view all the answers
In synthetic procedures involving nitration and alkylation, why is the order of reactions significant?
In synthetic procedures involving nitration and alkylation, why is the order of reactions significant?
Signup and view all the answers
Which of the following groups is known to withdraw electron density from the aromatic ring?
Which of the following groups is known to withdraw electron density from the aromatic ring?
Signup and view all the answers
What initial product is formed during Friedel-Crafts alkylation?
What initial product is formed during Friedel-Crafts alkylation?
Signup and view all the answers
What is the primary mechanism by which alkyl groups activate the aromatic ring towards electrophilic attack?
What is the primary mechanism by which alkyl groups activate the aromatic ring towards electrophilic attack?
Signup and view all the answers
Study Notes
Electrophilic Aromatic Substitution (EAS)
- EAS reactions involve the substitution of a hydrogen atom on an aromatic ring with an electrophile.
- Benzene's pi electrons, while stable in the aromatic system, are available for attack by strong electrophiles, forming a carbocation (sigma complex).
- Aromaticity is restored by loss of a proton.
- The intermediates (sigma complexes) in ortho and para substitutions are often more stable than those in meta positions, due to resonance interactions.
Specific EAS Reactions
- Halogenation: Use of halogen (Br₂ or Cl₂) and a Lewis acid (FeBr₃ or FeCl₃) as reagent.
- Nitration: Use of nitric acid (HNO₃) and sulfuric acid (H₂SO₄). Nitronium ion (NO₂⁺) is the electrophile.
- Sulfonation: Use of sulfuric acid (H₂SO₄), or Sulfur trioxide (SO₃) and sulfuric acid (H₂SO₄).
- Acylation: Use of acyl halide (RCOCl) and Lewis acid (AlCl₃).
- Alkylation: Use of alkyl halide (RX) and Lewis acid (AlCl₃).
Substituent Effects on EAS
- Electron-donating groups (EDGs): Activating groups that increase the rate of EAS, generally directing the incoming electrophile to ortho and para positions. Examples: -OH, -OCH₃, -NH₂.
- Electron-withdrawing groups (EWGs): Deactivating groups that decrease the rate of EAS, generally directing the incoming electrophile to meta position. Examples: -NO₂, -SO₃H, -CN, -CHO.
- Halogens: Although EWGs, they generally direct the incoming electrophile to ortho and para positions.
Friedel-Crafts Reactions
- Alkylation: Synthesis of alkyl benzenes using alkyl halides and Lewis acids (e.g., AlCl₃). Possible rearrangement of carbocation intermediates.
- Acylation: Synthesis of acylbenzenes using acyl halides and Lewis acids (e.g., AlCl₃). Products are less reactive than the starting benzene, so polyacylation is less likely.
Clemmensen Reduction
- Conversion of acylbenzenes to alkylbenzenes using amalgamated zinc (Zn(Hg)) and aqueous HCl.
Oxidation of Aromatic Side Chains
- Benzylic carbon can be oxidized, typically to a carboxylic acid by heating with basic KMnO₄ (or Na₂Cr₂O₇/H₂SO₄).
Aromatic Side-Chain Radical Halogenation
- Benzylic positions are highly reactive and preferentially halogenated (by Br₂ or NBS).
Regiochemistry of EAS
- The position of substitution on a poly-substituted benzene ring is determined by the substituents already present and their effect on electron density (activating or deactivating) and directing, leading to preferred ortho, para or meta positions.
Summary Table
- Refer to the provided image summaries for specific reactions and examples
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your understanding of Electrophilic Aromatic Substitution (EAS) reactions, where hydrogen on an aromatic ring is replaced by electrophiles. This quiz covers specific reactions like halogenation, nitration, and their mechanisms. Challenge yourself on stability of intermediates and substituent effects.
