30 Questions
What is the key intermediate in the Chlorination Mechanism?
Resonance Stabilized Intermediate
Which mechanism involves the formation of a Wheland Intermediate?
Chlorination
What type of intermediate is involved in the Iodination mechanism?
Resonance Stabilized Intermediate
In which mechanism is a Bromination Intermediate formed?
Nitration
Which type of intermediate is crucial in the Nitration mechanism?
Wheland Intermediate
What is the key feature of a Resonance Stabilized Intermediate?
Multiple resonance structures
Which mechanism involves the most stable intermediate out of the options provided?
Iodination
What distinguishes a Wheland Intermediate from other intermediates?
Positive charge on an sp3 hybridized carbon
In which mechanism is electron delocalization across the benzene ring most significant?
Chlorination
Which type of intermediate requires significant stabilization due to charge separation?
Wheland Intermediate
What is the defining reaction for electrophilic aromatic substitution (EAS)?
Resonance stabilized intermediate formation
What is another term used to refer to the species created in electrophilic aromatic substitution (EAS) known as s-complex?
Arenium ion
In electrophilic aromatic substitution (EAS), what role does the electrophile play?
It substitutes for a hydrogen atom on the benzene ring
What type of intermediate is formed during electrophilic aromatic substitution that is resonance stabilized?
Wheland Intermediate
What is the common term used for the resonance stabilized intermediate in electrophilic aromatic substitution reactions?
Wheland Intermediate
Which of the following is NOT a common name for the resonance stabilized intermediate in electrophilic aromatic substitution?
Carbanion
What type of bond is formed between benzene and the electrophile in electrophilic aromatic substitution?
Sigma bond
During electrophilic aromatic substitution, what is the role of halogenation?
Addition of halogen atoms to benzene ring
Which of the following reactions involve Friedel-Crafts Alkylation?
Alkylation of benzene
What is the general term for adding an acyl group to a benzene ring in electrophilic aromatic substitution?
'Acylation'
In the context of aromatic chemistry, what is a Wheland Intermediate?
A highly stable intermediate formed during electrophilic aromatic substitution reactions
What is the primary difference between Bromination and Chlorination mechanisms in aromatic chemistry?
The reagents used to generate the electrophile
Which of the following statements is true regarding the Iodination of aromatic compounds?
Iodination is generally more challenging than Bromination or Chlorination processes
What role does FeBr3 play in the Bromination mechanism in aromatic chemistry?
It acts as a Lewis acid catalyst to generate the electrophile
Why is Chlorination considered very similar to Bromination in aromatic chemistry?
They share a similar reaction mechanism with common intermediates
What distinguishes Friedel-Crafts Alkylation from Friedel-Crafts Acylation?
The type of electrophile used in the reaction
Which statement accurately describes the role of AlCl3 in chlorination reactions?
It acts as a Lewis acid catalyst to generate the electrophile
Which characteristic makes Iodination easier compared to Chlorination and Bromination?
'I2' is more electrophilic than 'Br2' or 'Cl2'
'FeBr3' used in Bromination serves mainly as what component?
'FeBr3' helps stabilize the Wheland Intermediate formed during reaction
In Friedel-Crafts Alkylation, what role does 'R-Br' play?
It serves as an electrophile to introduce an alkyl group onto the aromatic ring.
Study Notes
Aromatic Chemistry: Reactions of Benzene
- Electrophilic aromatic substitution (EAS) is a defining reaction of benzene, an electron-rich molecule.
- EAS involves the addition of an electrophile to benzene, creating a resonance-stabilized intermediate, also known as a Wheland intermediate.
Reaction Profile
- A reaction profile shows the energy changes during a reaction, with the reactants on the left and products on the right.
- The reaction profile of EAS shows the formation of a Wheland intermediate, which is a high-energy state.
Wheland Intermediate
- The Wheland intermediate is a resonance-stabilized intermediate formed during EAS.
- Its structure shows the delocalization of electrons, making it a stable species.
Electrophilic Aromatic Substitution (EAS)
- EAS is a general mechanism that involves the addition of an electrophile to benzene.
- The general mechanism involves the formation of a Wheland intermediate, followed by the loss of a proton to form the product.
Examples of EAS
- Bromination: uses FeBr3 and Br2 to form a brominated product.
- Examples of brominated products include Lonafarnib (an anticancer agent) and Bretylium (a treatment for irregular heart rhythms).
- Chlorination: uses AlCl3 and Cl2 to form a chlorinated product.
- Examples of chlorinated products include Indometacin (an NSAID) and Clorgiline (an antidepressant).
- Iodination: uses I2 and HNO3 to form an iodinated product.
- Examples of iodinated products include Calicheamicin (an antitumor agent) and Losartan (an antihypertensive).
Friedel-Crafts Alkylation
- Friedel-Crafts alkylation is a type of EAS that involves the addition of an alkyl group to benzene.
- The reaction uses an alkyl halide and AlCl3 as a catalyst.
- Examples of products include Cumene (a precursor to phenol) and Chlorambucil (a DNA alkylating agent).
Friedel-Crafts Acylation
- Friedel-Crafts acylation is a type of EAS that involves the addition of an acyl group to benzene.
- The reaction uses an acyl halide and AlCl3 as a catalyst.
- Examples of products include Raloxifene (an oestrogen receptor antagonist) and Lucanthone (an anti-parasitic agent).
Sulfonation
- Sulfonation is a type of EAS that involves the addition of a sulfonic acid group to benzene.
- The reaction uses SO3 and H2SO4 to form a sulfonated product.
- Examples of sulfonated products include Sulfanilamide (an antibacterial agent) and Sulfadoxine (an antibacterial agent).
Nitration
- Nitration is a type of EAS that involves the addition of a nitro group to benzene.
- The reaction uses HNO3 and H2SO4 to form a nitrated product.
- Examples of nitrated products include Chloramphenicol (an antibacterial agent) and Flutamide (an antiandrogen).
Summary
- EAS is a general mechanism that involves the addition of an electrophile to benzene.
- Examples of EAS include halogenation, Friedel-Crafts alkylation, Friedel-Crafts acylation, sulfonation, and nitration.
- These reactions form a wide range of products, including pharmaceuticals and agrochemicals.
Test your knowledge on Aromatic Chemistry with a focus on reaction profiles, Wheland intermediates, and examples of Electrophilic Aromatic Substitution (EAS) reactions. Explore key concepts covered in Slide 5 to Slide 8 of MPharm PHA111 lecture.
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