Aromaticity and Benzene Reactions Flashcards
Criteria for aromaticity
must be cyclic
must be fully conjugated
must be planar
must obey huckels rule (4n+2)
What steps are involved in creating Frost Circles?
Draw a circle, draw the molecule with the vertex pointed down, draw a horizontal line where the circle and ring meet, and fill with the appropriate amount of pi electrons
Aromaticity and lone pairs
lone pairs can exist in either hybridized or unhybridized p-orbitals; that may or may not contribute to aromaticity
Aromaticity and polycyclic molecules
Not all double bonds participate in aromaticity; look for the largest closed loop
Criteria for anti-aromaticity
obey all other rules for aromaticity, however, these do not obey huckels rule
Criteria for non-aromatics
does not obey one or more rules for aromaticity
Acidity and Basicity of aromatics
if deprotonation of the ring results in gaining/retaining aromaticity then the molecule is likely acidic; the more stable the conjugate base, the more acidic the molecule; via delocalization
pKa
dissociation constant of an acid; -log(Ka); the more negative the value, the more acidic the compound
Electron density
can be donated or withdrawn from a ring via induction and resonance
What to consider with inductive effects
electronegativity, polarizability, charges
polarizable alkyl groups
donate electron density (CH3)
Atoms with a positive charge
are electron withdrawing
what to consider with resonance
lone pairs and p-bonds
Neutral atoms on aromatic molecules
have opposing effects; resonance predominates over induction
Halogens on aromatic molecules
induction predominates over resonance
