6b Flashcards
what do gringard reagents like to do
they like to attack the carbonyl c,, they choose electrostatics over orbital overlap
they prefer direct addition
how can u make a gringard reagent undergo conjugate addition
u add copper chloride
it makes it into a soft nuc that prefers conjugate addition
preferring extensive orbital overlap rather than direct addition.
1-2 addition is
direct addition
1-4 addition is
conjugate addition
how does adding copper to a gringard reagent acc work tho
gringard reagent = XMgBr
where X is what u add to the moelcule.
by adding copper, u transmetalate the Mg into Cu.
XCuBr is softer than XMgBr,, correlating to 1-4 addition // conjugate addition
side produt for addition reactions with carbonyls
addition of the group u want,, then either an OH bonded to thae same carbon
or dehydration can occur which will leave the group u added, but remove the OH and form a double bond
which rate of reaction is higher,, the conjugate or direct addition,, when u have the same molecule for both but a copper and an mg molecule
the copper one is far more faster with its conjugate addition than the XMgBr and its direct addition
direct or conjugate addition? what should we look for
- type of nucleophile (hard or soft)
- type of molecule ( ewg or edg)
- reaction conditions (hot and long = conjugate,,, room temp + fast = direct)
is conjugate addition reversible
nope its irreversible
is dfirect addition reversible
yes
direct addition is reversible
u can go back to nuc and molecule
if conjugate addition is irreversible,, what does that tell us
that if u keep the reaction going,, the product formed by conjugate addition will increase slowly.
the more time u give the reaction,, the more conjugate addition will occur and the more product of that reaction will be.
kinetic product is the product that is formed fastest so its the
direct addition product
the thermodynamic product is the more stable product,, this is the
the conjugate addition product,, bc u still have the super strong C=O sigma bond!! which u lose with direct addition.
kinetic control includes
low temp + short reaction times
thermodynamic control includes
higher temps and longer reaction times
NaBH4 rea
acts as an electrophile,, it basically does a conjugate addition to remove the double bond and give an alkane
when u do a conjugate additio u normally need to have a brief what
a brief negative charge as ur moving e-,, and ewg can hold this charge and then resonate it to the double bond which can aatack and H from the solvent to saturate the moelcule. doing from a double to a single bond.
are 1-6 additions a thing
yes
there are zero nodes for pi 1
all p orbitals must be in phase
what is a conjugate substitution
a cojugate addition followed by an elimination
what is needed for a conjugate substitution reaction
there must be a good leaving group on the beta carbon
describe a conjugate substitution reaction
conjugate addition occurs,, double bond is resonated onto the carbonyl or the ewg (cn or no2)
the - on the ewg or o (enomlate) is then used to kick off the good leaving group that is on the beta carbon.
there should be e configuration
vinylogous behaviour,,
the conjugate double bond links the carbonyl and the heteroatom so it has similar chem and spectroscopic behaviour to its simpler version (carbonyl with the heteroatom directly bonded to it)
