2c Flashcards
describe a synthetic equivalent aka what is it and give us examples
synthetic equivalents are stuff that havr the same characteristics,, something that reacts in the same // similar way
: CH3-Br,, CH3-OTs,, theyre both synthetic equivalents of eachother bc theyre all CH3-LG,, and react the same with OH- to give CH3-OH
when we have smt with a double bond // an aromatic with multiple double bond,, what prefic is added to tell us that hydrogens were added to the compound to saturate the unsaturated bonds
we add the prefix ‘hydro’
we can add ‘dihydro’ or ‘tetra hydro’ to show how many H’s we are adding.
dihydro meaning
we’re adding two hydrogens to a compound to saturate unsaturated double bonds
bc were adding 2 hydrogens bc of the ‘di’ this tells us that one full double bond is swapped to a single bond!! bc 2 H’s is what is needed to go from a double to a single bond!!!
what is meant by tetra hydro
this is where 4 H’s are added to a compound to saturate any unsatured bonds
in this case we wrote ‘tetra’ which means 4. which means 4 H’s were added which means 2 unsatured double bonds can be saturated to give 2 single bonds!!!
describe hybridisation in benzene
in benzene the C’s are sp2 hybridised,, with 1 all the sp2 orbitals used for bonding ,, and 1 leftover electron being in the p orbital,, which constructively overlap to give a pi system,, aka aromaticity.
describe pyridine
pyridine is a benzene but it has N instead of one of the C’s
describe the bonding in pyridine
the C’s are obvs still sp2 hybridised with 1e- in their p orbitals which overlap to give the pi system!!
the N has one extra electron tho,, so its also sp2 hybridised and has 1 electron in its p orbital,, but it also has 2 electrons in an sp2 orbital. these are orthogonal to the pi system and thereofre conjugation with them cannot occur!!
the p orbital and the sp2 orbitals are orthogonal!!!
what is the lone pair on N in pyridine and what can it be used for
its in an sp2 orbital,, orthogonal to the p orbitalssss with 1 e- in them.
this means they cannot be included in conjugation but they are nucleophilic and basicccc..
meaning they can be donated to other stuff during reactionss
describe pyrrole
pyrrole is a 5 membered ring with 2 double bonds and N as one of the members
theres a H attached to the N!!
describe the bonding and hybridisation in pyrrole
the C is sp2 hybridised obvs with 1 e- in their p orbitals forming a pi system
the N has 5 valence e- : its sp2 hybridised and so has 1 e- in each orbital ( 2 C’s and 1H) (5-3 = 2) then theres 2 left,, these go into the p orbital.
the lond pair can be conjugated as it does overlap with the p orbitals of the C,, this means that conjugation can occur!!!
can the p orbital with a lone pair in the pyrrole of the N be part of the pi system and be involved with conjugation
yessss
bc the p orbitals have constructive overlap!!!! this means that they overlap!!!
is pyridine or pyrrole e- deficient
pyridine is e- deficient
what does it mean when we say pyridine is e- deficient?
this is the one with 2 e- as a lone pair,, in the sp2 orbital meaning its orthogonal tp the p orbitals
this means electrophiles (things that like negative charge are added to the N,, bc it has e- pairs)
pyridine and AlCl3
the Al in AlCl3 is slightly positive bc the Cls’ are electronegative and pull e- density away from it.
the lone pair on the N is basic and nucleophilic and so attacks the Al of AlCl3. the AlCl3 is then bound to the N.
the N becomes (+) and the AL becomes (-)
when something bonds to the N in pyridine,, what do we say happens to pyridine
we say that it becomes deactivated!!!
what can the N in pyridine attack
the N in pyradine (benzene with a N that has a lone pair in its sp2 and 1 e- in their p) can acts as a base and as a nucleophile.
meaning it can attack things that have a slight positive charge.
what type of reactions dont work on pyridine.
electrophilic aromatic substitutions dont work on pyridine type systems!!!!
bc we obvs dont want to lose aromaticity.
pyridine and electrophiles!!!!! what position//C is most likely to have the electrophile added to it and why
the N is normally labelled as 1,, the c’s next to it can be 2, 3, 4, etc!!
C2 and C4 (ortho and para) will not happen bc the (+) will land on the N,, N is electronegative and so this isnt a stable interaction bc hello lols.
so it would normally be added onto C3,, which is the meta position,, mostly bc this is the meta position,, which means the (+) would not be placed on the N but on the C’s. which still isnt that stable, but its more stable than it being on the N.
why is it difficult for electrophilic attakcs to occur in pyridine
bc the electrons given by N,, lower the energy of the pi system compared to benzene.
lowering of energy means its more stable. so less likely to be altered.
what do we call it when pyridine is reacted with a nucleophile
this is like a SnAR reaction. ]
nucleophilic substitution reaction on aromatics
describe SNAr on pyridine
its basically conjugate addition.
like theres a halogen bonded orhto or para to the N. and the nuclophile attacks the C the halogen is bonded to and resonates the double bond e- onto the N. (ewg)
the (-) on N is then resonated back up and kicks off the original substituent!!!! leaving the nucleophile that attacked it.
when we think of pyridine and SNAR,, what should we think offf
we should think of an immine
the double bond carbonyl thing but instead of an O its a N!!! <3
describe pyrrole again
5 membered ring
N is one of the members
N has 2 e- in the p orbital
1 e- in each sp2 orbital
is pyrrole e- deficient or e- rich
its e- rich!!!! pyridine is e- poor
when we are thinking about the diff reactions pyrrole can undergo being e- rich,, what should we think of
we should think of enolates // enols,, where the C is nucleophilic and can attack nucleophiles!!
this is by using the O- on the O to resonate onto the double bond to the double bond can attacks smt else.
