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In general, what differentiates activating groups from deactivating groups?
Activating groups have a lone pair that can be donated into the ring. Because the ring is acting as the nucleophile, this resonance increases the nucleophilicity.
Deactivating groups act as EWG's and decrease the nucleophilicity so that the ring has a harder time acting as the nucleophile.
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Activators are _____ directors, while deactivators are ____ directors
Ortho/para
Meta
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In the reaction coordinate diagram, structures that include EDG (activators) will be ____ than benzene, while structures that include EWG (deactivators) will be ____ than benzene
Lower
Higher
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When EAS takes place on a ring with more than one substituent, what decides where the new addition will go?
The stronger activating group decides
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In EAS the ring acts as the ____ while in SNAR it acts as the _____
Nucleophile
Electrophile
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When looking at pyridine and pyrrole, how can you tell what the major product will be?
Determined by number of resonance structures. The more structures, the more stable the product will be
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What is azo coupling?
Occurs when one molecule with a n-n triple bond interacts with a ring that has a n with l.p.
Forms a double nitrogen bond connecting the two rings
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What is nucleophilic aromatic substitution (SNAR) and what is required for it to work?
Occurs when there is a leaving group on the ring and it is replaced by a nucelophile.
For it to occur there needs to be a decent EWG o/p to the leaving group because a negative charge will form on the ring and we want the EWG to help stabilize it
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What is the major restriction on SNAR?
The leaving group has to be more stable as an anion than the nucleophile
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Does pyridine participate in EAS or SNAR?
SNAR because it can have a negative charge on the nitrogen and it prefers that over the positive
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What is benzyne?
An intermediate with a triple bonded carbon in the ring. It's very unstable and exists only as a transition state
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Why is sulfonyl a good blocking group, and what does it show up as on the ring?
It is a reversible reaction, so it can be removed after the substituent has been placed in the right orientation. It shows up on the ring as SO3H
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What is another option for a blocking group besides SO3H? Why does it work?
NH2
It is a strong EDG, so it helps make the ring more nucleophilic
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Pyridine is _____ towards EAS while pyrrole is _____
deactivated (activates to SNAR)
Activated
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Why is pyrrole activated to EAS?
The lone pair in pyrrole is needed for aromaticity so it cannot be protonated
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Why is pyridine deactivated towards EAS? (Activated to SNAR)
The lone pair on N is not needed for aromaticity, so it can be protected and turned into an EWG
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What happens to aniline when it is treated with acid chloride or acid anhydride with a Lewis acid catalyst?
It becomes the amide. It becomes a moderately EWG, because the L.P on the nitrogen can also be delocalized into the carbonyl bond
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