Aromatics Flashcards
Aromaticity
What makes a system aromatic or not aromatic.
4 conditions of Aromaticity
- Cyclic
- Each carbon is sp2
- Continuous loop of p-orbitals
- Hachel’s Rule satisfied
Hachel’s Rule
of e- in p-loop = 4n+2 or # of π e- = 4n + 2
Parent name for simple compounds
Benzene
Nitro
NO2
NH2 attached to benzene
Aniline
isopropyl attached to benzene
Cumene
ethene attached to benzene
Styrene
OH attached to benzene
Phenol
Carbonyl attached to benzene
Benzaldehyde
Carboxylic acid attached to benzene
Benzoic Acid
Ether attached to Benzene
Anisole
Ketone attached to Benzene
Acetophenone
Dimethylbenzene
Zylene
Electrophilic Aromatic Substitution, why does it include the word “substitution”?
Hydrogen is being substituted for electrophile.
Electrophilic Aromatic Substitution Requirements
Strong Electrophile, Look at resonance (at least 3)
Is the carbocation intermediate of the electrophilic aromatic substitution stable? Why?
It is stable, because it is resonance stabilized.
Steps of Electrophilic Aromatic Substitution
- Formation of Electrophile
- Formation of Arenium Ion
- Regeneration of Aromatic Ring
halogens don’t like what?
positive charge
Chlorination and Bromination Requirement
Requires Lewis Acid Catalyst
Lewis Acid Catalysts
For Cl2: FeCl3 or AlCl3
For Br2: FeBr3 or AlBr3
Nitric Acid
HNO3
Which one is a stronger acid? Sulfuric Acid or Nitric Acid?
Sulfuric Acid (H2SO4) is a stronger acid than HNO3
Bronsted Lowry Acid
Proton donor (not an acceptor like Lewis Acid)
Bronsted Lowry Base
Proton Acceptor
Required reagents for nitration
Nitric Acid, Sulfuric Acid, and heat
Difference between nitration, sulfonation, and halogenation
Only difference is how you form electrophile.
Required reagents for sulfonation
SO3 and H2SO4
SO3
Sulfur Trioxide.
Sulfonation resulting product
Benzene sulfonic Acid - SO3H added to Benzene
Thing to remember about carbocations
LOOK FOR REARRANGEMENT
How many products are generated from friedel-crafts alkylation?
2 without resonance, 1 without rearrangement (minor)
Friedel-Crafts Alkylation Limitations
Rearrangement possibility and Electron withdrawing groups
Why are electron withdrawing groups a limitation for Friedel-Crafts Alkylation?
Electron Withdrawing groups reduce the electron density of the ring and make it less likely that electrons will go to chloride, resulting in no reaction.
Required Reagent for Friedel-Crafts Acylation
Acyl Chloride and AlCl3 like alkylation
Limitation of Friedel-Crafts Acylation
Rearrangement still can occur.
Electrophile used for Friedel-Crafts Acylation
Acylium ion
What limitation does Friedel-Crafts Acylation resolve?
Electron withdrawing group results in no reaction - problem of Alkylation
What does Clemmensen Reduction do?
Remove ketone after acylation.
What we don’t need to know about Clemmensen Reduction
its mechanism, just now its reagents.
Where is the benzylic carbon?
First Carbon attached to Benzene
Oxidation at Benzylic Carbon results in what?
Formation of Carboxylic group
Oxidation at Benzylic Carbon requires what reagents?
KMnO4, heat, H3O+, and NaOH
What leads to no reaction for oxidation at Benzylic Carbon?
Benzylic carbon has no hydrogens and no π bonds.
Downside of oxidation at benzylic carbon
Difficult to control, affects multiple functional groups
Oxidation at benzylic carbon further group terms for pi bonds
Alkenyl group, Alkynyl Group
Ortho and Para products. Which on is major? Why?
Para, because of steric effect. (less steric hindrance)
First substituent has what effect on the second substituent?
The first substituent has two effects on the second substituent: the first substituent can either be ortho/para directing or meta directing, and the first substituent can alter the rate of the second substituent. Activating = speeds up reaction, deactivating = slows down reaction.
What mechanical way determines whether a substituent is ortho/para directing or meta directing?
Number of resonance structures and full octet.
Ortho/para directors characteristics
Ortho/para directors have a lone pair of electrons and are electron donating.
Meta director characteristics
Electron withdrawing (except halogens).
Common ortho/para directors
-OR, -NR2, -R, -X (inappropriate films) - R=alkyl, acyl (carbonyl), H
Activating Substituents characteristics
Usually ortho/para directors excluding halogens.
Deactivating Substituents Characteristics
Electron withdrawing groups
Why are most electron withdrawing groups deactivators?
Because they reduce electron density of the ring, slowing down the reaction.
In order to add a third substituent, which substituent is the driving force behind determining where it will go?
Activating substituent is stronger than the deactivating substituent, so it will determine where the third substituent goes.
TNT
2,4,6 - Trinitrotoluene
