Aromatic Chemistry Flashcards
What are aromatic compounds
Cyclic structures with enhanced stability due to an overlapping pi system
Huckles rule
Compound only aromatic if it is planar, fully conjugated and contains 4n+2 electrons
Advantages of aromatics in drug design
• planar structure
• Rigid - defined shape
• involved in certain intereactions : hydrophobic interactions and pi-pi stacking
• Hold substituents in defined positions
Important characteristics of aromatics
• Cyclic
• Identical bond lengths
• Planar
• Rigid
• All C atoms sp2
• Delocalised e-
• Very stable thermodynamically
• React via substitution not addition reactions
Phenyl vs Benzyl groups
Phenyl = hexagon with double bonds
Benzyl = same but has a CH2 attatched
Where is ortho, meta and para
Ortho is either side of the top C
Meta is the 2 below these
Para is the bottom C
What does a fully conjugated aromatic need?
A catalyst for the reaction to move forward
2 features of electrophillic addition
Nothing leaves and between alkene and electrophile
How do substituents effect reactivity
Depends on the substituents as well as its position on the aromatic ring
E- withdrawing groups….. the ring and E- donating groups….. the ring
Withdrawing - deactivate/destabilise = less reactive than benzene
Donating - activate/stabilises = more reactive than benzene
What part of the ring does donating groups activate?
Ortho or para
What part of the ring does withdrawing groups de activate?
Ortho or para
Whatever the nature of the X substituent which position feel the effect the most?
Ortho and para
3 groups of effects
- Ortho and para directing activators
- Ortho and para directing deactivators halogens
- Meta directing deactivators
Reactivity and orientation are controlled by….
Inductive and mesmeric effects
