Electrophilic Aromatic Substitution Reactions Flashcards
Does bromination of benzene occur at room temperature?
No
Name a catalyst for the bromination of benzene
Iron (3) bromide FeBr3
What reagents are used in the nitration of benzene and why?
Concentrated nitric and sulfuric acids
- To obtain a nitronium ion
- sulfuric acid acts as a catalyst
Name the reagents in the reduction of a nitro group(addition of hydrogens)
Zinc, tin or iron
Aqueous HCl
Name a use for the reduction of of a nitro group
Is the best method for adding an amino group to the ring in the production of many dyes and pharmaceutical agents
How much faster does toluene react than benzene and why?
25 times faster, methyl group is an activator
Explain the effects of alkyl groups in reactions of benzene
They are activating substituents and ortho and para directors
Explain the effects of alkyl groups in reactions of benzene
The inductive effect- alkyl groups can increase electron density to the ring via the sigma bond making the molecule more active
In nucleophile aromatic substitution, what determines where the nucleophile attacks
Where the leaving group is
In electrophilic aromatic substitution, what determines where the electrophile attacks?
Electronic and steric factors( mix of ortho and para products)
Name one limitation of friended-Crafts reaction that limits its reagents
F-C reactions only work with benzene, activated benzene derivatives and halobenzene, failing on deactivated benzene rings as they are less reactive
Are F-C reactions susceptible to carbocation reagents?
Yes
Is the alkylbenzene formed by the F-C reaction more reactive than benzene and what is the consequence?
Yes, causing polyalkylation to occur
Name the catalyst for the bromination of benzene and its purpose
FeBr3 - makes Br2 more electrophile by reacting with it to give Br+ and FeBr4-
Describe the carbocation intermediate between benzene and Br+
It is not aromatic, doubly allylic and is a hybrid of 3 resonance forms
Name the reagents for silfonation of benzene
Benzene
Sulfate ( SO3)
Catalyst: sulfuric acid
Product: benzenesulfonic acid
Name one use of the sulfonation of benzene
Key step in the synthesis of compounds such as the sulfa drug family
What are the catalysts of the desulfonation reaction?
H+ and heat( can be accomplished by heating dilute sulfuric acid)
Name the activators of benzene in order of strength
Phenoxides (O-), anilines, phenols( OH attached), phenyl ethers ( O-R group attached), anilides, alkylbenzenes
Name the deactivated groups for benzene
Nitro group, sulfonic group, cyano group, ketones or aldehydes, ester, quaternary ammonium
What do all activators have in common?
Are either R groups, or have an N or O atom with a lone pair directly bond to the benzene ring(electron- donor groups)
What do all deactivators have in common?
All deactivators are either halogens, have in atom with partial or full positive charge bonded directly to the ring( electron withdrawing groups)
How does CN affect orientation of a reaction?
CN is a meta director
How does OH affect the orientation of a reaction?
OH is an ortho and para director
Is benzoic acid more or less reactive than benzene?
Benzoic acid is less reactive than benzene
Which are usually stronger directors? Activating groups or deactivating groups?
Activating groups?
What is another term for dimeyhylbenzene?
Xylene
How do halogens change the orientation of a reaction?
Ortho and para directing
How do all deactivators except halogens affect the orientation of a reaction?
Meta directors
What kind of directors are all activating groups?
Ortho and para
How do alkyl groups affect reactivity of benzene( describe the process)
The inductive effect- alkyl groups donate to the electron density to the ring through the sigma bond, making it more reactive
