Aromatic and Heteroaromatic Chemistry Flashcards
Arenes
aromatic hydrocarbons (C and H atoms only in the ring)
Polyarenes
polycyclic aromatic hydrocarbons
Heteroarenes
aromatic compounds that contain also a heteroatom in the ring (N,O, S…)
regioisomers
constitutional isomers that have the same functional groups attached at different positions of the molecular backbone
Furfural
Furan-2-carbaldehyde is an important renewable non-petroleum based, chemical feedstock which can be converted into solvent, polymers, fuels, etc
Lignin
Class of organic polymers made by cross links among various phenolic precursors.
Has a structural role in plants (cell wall). After cellulose, it’s the most prevalent biopolymer and potentially a biofuel.
Aromatic system defined
cyclic, planar, fully conjugated and contains (4n+2) ⫪ electrons (Hückel’s rule n≥0)
Antiaromatic system defined
cyclic, planar, fully conjugated and contains (4n) ⫪ electrons (n≥1)
What are antiaromatic systems like?
they are destabilised, i.e. they are higher in energy, hence they are very reactive and rather unstable and often require isolation at low temperature
Annulenes
monocyclic hydrocarbon compounds with the maximum possible number of non-cumulated double bonds
Can annulenes be aromatic?
Annulenes can be aromatic, antiaromatic and non-aromatic - it depends on the number of their ⫪ electrons AND whether they are planar or not
Diamagnetic anisotropy
Different magnetic fields are found at different points in space due to fields induced by circulating electrons
What is the cationic intermediate in electrophilic aromatic substitutions called?
- Wheland intermediate
- Arenium ion
- σ complex
Why is the cationic intermediate in electrophilic aromatic substitutions higher in energy?
it is a resonance stabilised cation, but it isn’t aromatic
How does sulfonation vary with temperature?
- At high temp = thermodynamic products (reversible)
- At low temp = irreversible therefore kinetic products
