In an EAS, what is the nucleophile?
Aromatic ring
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| Term | Definition |
|---|---|
In an EAS, what is the nucleophile? | Aromatic ring |
What does the nucleophile use to attack the electrophile? | Pi e- (DB) |
What is the RDS in an EAS? Why? | - The first step is RDS
- Aromaticity is being disrupted = unfavorable = slow |
Anything to stabilize the TS will _____ the rxn rate | Speed up |
T/F: The carbocation intermediate of an EAS is not resonance stabilized | False |
Is the final step of an EAS fast or slow? Why? | - Fast
- Restores aromaticity |
Intermediate vs TS | Intermediate: species that exists between R and P in a state corresponding to energy MINIMUM
TS: High energy arrangement that represents bonds breaking/forming during mechanism |
What is the product of aa FC alkylation? | Alkylbenzene (PhR) |
What is an FC alkylation activated by? Why | Lewis Acid
- AlCl3, FeBr3
Alkyl halide is made more electrophilic w/ lewis acid |
What solveny you need for a FC alkylation? | Lewis acid + alkyl halide |
For primary alkyl halides, what is the electrophile? | Lewis acid-alkyl halide together |
For secondary and tertiary alkyl halides, what is the electrophile? | The carbocation |
T/F: Primary carbocations are stable | False, they're very unstable |
What will FC alkylation's not react with? Why?
2 | Vinyl or aromatic halides
- Cannot participate bc halide is already on an sp2 carbon |
T/F: any conditions that generate carbocations can lead to FCA | True |
Alkene + acid = | Carbocation |
What 3 things will only react in FCA? | - Benzene
- Halobenzene
- Electron rich benzene |
Does overalkylation occur? Why? | Yes
- Alkyl groups are EDG = aromatic ring is more e- rich and more nucleophilic |
T/F: EWG are not good for FC rxns | True |
What conditions do you need for oxidation to generate a CA at benzylic carbon? | 1. KMnO4, KOH, heat
2. H3O+ |
The oxidation rxn converts a _______ to an ______ | EDG (alkyl) to a EWG (CA) |
What is the product of an FC acylation rxn? | Acylbenzene (PhCOR) |
What two things does an FC acylation occur between? What is it activated by? | - Acid halide/anhydride and benzene
- Lewis acid |
What is the electrophile in the FC acylation rxn? | Acylium ion |
Is overacylation a problem? Why? | No
- Acyl groups are EWG = aromatic ring is e- poor and less nucleophilic |
What is used in the Clemmensen reduction? | - ZnHg
- HCl |
What is done in the Clemmensen reduction? | Reduce a C=O to a methylene (CH2) group |
The Clemmensen reduction converts a ____ to a ____ | EWG (acyl) to a EDG (alkyl) |
What activates Br2 during bromination? Why? | FeBr3
- Makes it more electrophilic |
What do you need for a bromination rxn?
| Br2
FeBr3 |
What do you need for a chlorination rxn? | Cl2
AlCl3 |
What are the end products of bromination?
3 | Bromobenzene
HBr
FeBr3 |
What are the end products of chlorination?
3 | Chlorobenzene
HCl
AlCl3 |
What do you need for an iodination rxn? | I2
HNO3 |
What are the end products of iodination? | Iodobenzene
NO2
H2O |
What is the nitration rxn accelerate by? | H2SO4 |
What do you need for a nitration rxn? | HNO3
H2SO4 |
How can nitrobenzene be reduced to anilines? | - Zn, HCl
OR
- H2, Pd |
The reduction of nitrobenzene to aniline converts a ____ to a _____ | EWG (NO2) to a EDG (NH2) |
What do you need for the sulfonation rxn? | SO3
H2SO4 |
Is sulfonation reversible? | Yes |
How can you remove HSO3 from benzene? | H2SO4
Steam (H2O + heat) |
T/F: the less e- density in the ring, the better the nucleophile | False |
EDG ______ reactivity | Increase |
Are activators EDG or EWG? | EDG |
EWG _____ reactivity | Reduce |
Which effects are more significant? Resonance or induction? | Resonance |
What are the strongest to weakest activators?
6 | 1. O-
2. NH2
3. OH
4. OR
5. NHCOR
6. R |
What are the strongest to weakest deactivators? | 1. NO2
2. HSO3
3. CN
4. COR
5. COOR
6. NR3+ |
For alkyl sub, what substitution would you see? | O/P
- Para for big groups |
Increase in the size of alkyl groups mean it goes from ____ to _______ | Ortho to para |
Alkyl groups are ______, ________ - Directing groups | Activating, O/P |
Methoxy groups are electron______ and ____ the reactivity of benzene | Donating groups and enhance |
Methoxy groups are _______, ______-Directing groups | Activating, O/P |
Amino groups are electron______ and ____ reactivity of benzene | Donating and enhance |
Ammonium groups are electron__________ | Withdrawing |
The amino group is ________, _________-Directors | Activating, O/P |
Nitro groups are electron________(_____&____) and _____ reactivity of benzene | - Withdrawing (resonance & induction)
- Decrease reactivity |
If you have a decreased reactivity, will the rxn go slower or faster? | Slower |
EWG ______ the carbocation intermediate = _____ rate of rxn | - Destabilize
- slower |
For EWG, which intermediate is harder to form? | High energy |
Nitro groups are _______, ________-directors | Deactivating, meta |
What are some EWG?
5 | - Ketones, esters, nitriles, sulfonic acid, ammonium salt |
Halobenzenes are _____ to react than benzene | Slower |
How can halogens influence EAS rxns?
2 | 1. They are electronegative and deactivate the ring inductively
2. Donate e- density via resonance and activate through formation of halonium ions |
Halogens are _______, ________-directors | Deactivating, O/P |
Should you place a new group between substituents? | NO |
If two substituents on a benzene ring have opposing effects, what are the 3 ways you decide where to place the new sub? | 1. Strongest activator wins: OP directors that stabilize carbocation's through resonance
2. Intermediate directors: OP directors
3. Strongest deactivators are the weakest |
In NAS, what is the electrophile? | The ring |
Compounds that undergo EAS are electron-________, and those that undergo NAS are electron_________ | - electron rich
- Electron poor |
When is addn-elim common? | When one+ EWG located OP to substitution site |
EWG oriented in ______ position have left effect | Meta |
When is the benzyne mechanism appropriate? | In rings w/o many EWG |