9 - HETEROCYCLES Flashcards
why is pyridine a weaker base than piperidine?
what are some natural and synthetic derivates of pyridine?
how do orbitals affect acidity and basicity?
how does electronegativity play a role in acidity/basicity?
how is pyridine formed from an unsaturated 1,5-dicarbonyl compound?
how is pyridine formed from a saturated 1,5-dicarbonyl compound?
how is dihydropyridine reduced to aromatic pyridine by DDQ?
what is the mechanism of the Hantzsch pyridine synthesis?
which carbon substitution does pyridine prefer?
C3 substitution is preferred
this maximises the number of resonance forms possible in the intermediate, greater charge delocalization
what are some C3 substitution that pyridine undergoes?
why is N substitution for pyridine preferred and what are some reactions?
why is pyridine reluctant to undergo electrophilic aromatic substitution?
on which carbon does pyridine prefer doing electrophilic aromatic substitution?
C3
more resonance forms, greater charge delocalisation
be able to draw the resonance structures:
how do we carry out reactions at C4 for pyridine?
first prepare a Py N oxide by reacing with H2O2 then add the desired nucleophile
reduce it back to the ring
you get some C2-nitro derivatives, but that one is less favored because of sterics and electrostatic repulsion between N+ and NO2+
How is the C4 NO2 pyridine reduced with trimethyl phosphite?
trimethyl phosphite is a reducing agent