8c Flashcards
cyclopropane description
triangle
azinide description
triangle with NH as one of the verticles
epoxide description
triangle with an O as one of the vertices
azetidine description
box with nh as one of the vertices
oxetane description
box with o as one of the vertices
pyrrolidine description
pentagon with nh as one of the vertices
tetrahydrofuran description
pentagon with an o in one of the corners
ribose description
pentagon with o as one of the vertices and oh bonded to every other vertice.
piperidine description
hexagon with nh as one of the vertices
tetrahydropyran description
hexagon with o as one of the vertices
dioxane description
hexagon with 2 o’s as vertcies
theyre like on either side of the molecule.
piperazine description
hexagon with nh on either side of the molecule.
1 bond forming strategy includes the use of what
nucs and electrophiles
2 bond forming strategy can occur due to what two things
- en reagents : carbene etc
- enoid : peracid // mcpba
whats an ‘en’ reagent
a reagent where the molecule ormally has 2 e- less than the full valence count.
this makes them unstable and hard to make
describe a carbene
it has 6 valence e-
its an sp2 hybrid
so all 3 sp2 orbitals are full: meaning theres a lone pair in an sp2 orbital what can be used as a lone pair meaning its nucleophilic.
theres an empty p orbital which is the electrophile as e- can be accepted here.
whats cool about the ene reagents
u can form 2 bonds bc theyre nucleophiles and electrophiles at the same time.
how do we form a CH2 reagent thats an en reagent meaning its a nuc and electtrophile at the same time
u take NH2CH2 and put energy into it.
this forms CH2
which has an empty p orbital for the electrophile
and a lone pair in the sp2 orbital
how does CH2 work as a en reagent : describe the reaction with CH2 and butene
the sp2 lone pair attacks the double bond of the alkene
the double bond of the alkene attacks the empty p orbital on the CH2.
u form a cyclic structure: cyclopropane with methyl substituents
whats cool about the en reagent reaction where its a nuc and electrophile at the same time
its a concerted reaction!
means it all happens at once
it also means that stereochemistry remains the same!!
along with en reagents,, whats the other reagent that can be used as a nuc and an electrophile and why is this one slightly diff to the ene ones
these are the enoid reagents.
theyre diff as they have a full valence e- count meaning theyre not missing out on any electrons
this makes them more stable + easy to make.
their reactivity is the same as the en specie
example of the enoid
mcpba
what part of mcpba makes it an enoid
the oxygen of the OH!!
aka the ocygen closest to the end.
bc its got 2 lone pairs
and the mcba bit kinda looks like a carboxylic acid,, which can form a stable ion,, aka a good LG!! so the alkene double bond can attack the O of the OH ,, e- can go into the O-O sigma* antibonding orbital to break that bond and form the anionic carboxylic acid thing.
then this can take the H on the epoxide to form a carboxylic acid and a neutral epoxide
C- X where X is a halogen,, what is C
C would be an electrophile as the halogen removes e- density from it
allowing it to accept e- from the nucleophile and kick off the halogen
C - MgBr or metal ,, what is C
the C – metal bond is the nucleophile!!
meaning it can ttack things
C- X and then u add a metal,, what happens
u get C - Metal - X
CH2I2 + Zn
describe everything about the product
u have H, H, I, C - Zn - I
the C - I bond will be an electrophile
the C - Metal - I bon will be the nucleophileee
so we have another enoid reagent iggg
bc its nucleophilic and electrophilic at the same time. with full valence,, its not missing any e-.
if u react it with cyclohexene u get cyclohexane with CH2 in an epoxide type structure, aka the CH2 just kinda sticks out
okay describe what 2 reagents are used in a diels alder reaction
- diene
- dienophile
describe a diene,, the diff ones and what one u need for the diels alder reaction
u need the s- cis diene in the diel alder reaction!!!
s for sigma
what is the diels alder reaction a type of
its a type of a 2 bond formation reaction
what is a dienophile
smt that likes dienes!!
its basically an ethene with a methyl ester one the ethene carbons
describe the diels alder reaction : the mechanism etc
so u have the diene and the dienophile!!
the dienophile attacks the up space between then to form a bond
the double bond of the diene is moved to the middle section of the diene
the other double bond of the diene attacks the down space between the diene and the dienophile to form another bond
u form a cyclic structure with a double bond in it ( the double bond of the diene that moved to the position next to it)
whats the driving force of the diel aldes reaction
the driving force is the good orbital overlap between the homo and the lumo of the diene and the dienophile.
the orbitals on the end match up to the end orbitals on the other structure, aka theyre both shaded or not allowing constructive overlap !!!
how do u figure out the pi stuff for diene
u cout how many pi e- there are
aka if u have 2 double bonds u have 4 pi e-
so 2 e- levels will be filled with an e- pair.
then we draw the energy levels,, so like if have 4 e- levels,, u do 4/2 so u have pi1 and pi 2 and the pi1* and pi2* ,, so u have the bonding and antibonding versionsss
so for diene if its butadiene u have 4 pi e-,, so 2 pi level will be filled,, meaning u need the corresponding pi* for each of them!!
pi levels for dienophiles
count the number of pi e-
if theres 2 pi e- u only need 1 energy level for them to fill up so pi 1
and thn u need the antibonding equivalent,, so pi 1* aswellllll.
whats the stereoelectronic effect on ethane,, describe it
any effect on the structure , reactivity or other properties of a molecule that is caused by the spatial position of the molecules orbitals - newman projection etcccc
what is the anticonformation in ethane and explain it
sigma CH can interact with the CH sigma** of the other bonds and this interaction is maximised in the anticonformation!!
its when theyre staggered kinda!! the bonds are all seen rom the newman projection!!!
