Chem 261 mechanisms Flashcards
what conditions give the anti-Markonikov product?
HBr and Peroxide (ROOR)
Steps of acid catalyzed alkene hydration
- acid protonates alkene (C=C bond broken, C-C remains)
- water (Nu-) added –> OH group added to alkane
Oxymercuration/Demercuration steps
- oxymerc. –> addition of HgOAc and OH (reactants: H2O, Mg(OAc)2, THF)
- demerc. –> removal of HgOAc and addition of H (Reactants: NaBrH4
*** NO rearrangements –> no carbocation intermediate
3 mechanisms of alkene hydration:
- acid catalyzed
- oxymerc./demerc.
- Hydroboration-oxidation
Hydroboration-oxidation steps
- hydroboration –> addition of BH2 and H (syn)
- Oxidation –> removal of BH2 and addition of OH
dihalogenation of an alkene steps
- addition of br or cl, 3-membered transition state
- addition of other br or cl from other side (syn addition)
reactants in halohydration of alkenes
H2O and X2 (X = Cl or Br)
Halohydration adds ___ and ___ across a C=C bond
OH and X (X = Cl or Br)
2 options for conditions of 1,2-dihydroxylation:
1.) dilute KMnO4/HO-/H2O/cold
2.)OsO4, pyridine then NaHSO3, H2O
Dihydroxylation of an olefin with OsO4 (list steps and other conditions)
- OsO4 and pyridine –> intermediate with Os
- react with NaHSO3 and H2O –> product is formed
reactants in oxidative cleavage of alkenes
O3 (ozone), Low temp
–> and a reductive or oxidative workup
Steps of oxidative cleavage of alkenes
- add O3 with low temp, as well as a reductive/oxidative workup
- results is fragments due to breaking of double bond (2 carbonyl fragments)
why is a phenol not an alcohol?
The OH group is attached to an SP2 C and not a SP3
Steps of converting an alcohol to an alkyl halide with PBr3
- protonate OH with PBr3
- PBr2 attaches, Br leaves
- Br attacks from bottom, OHPBr2 leaves
- alkyl halide remains
What is the purpose of protonating alcohols
To make them into better leaving groups
acronym for an OH protecting group
TBSCl or TBS
what is TBAF used for
to remove an alcohol protecting group (ie. TBS)
It is a source of fluoride
what can you treat an alkene with that results in an epoxide?
MCPBA (a peroxy acid)
Acid catalyzed ring opening of an epoxide results in the ____________ product while basic conditions result in the _____________ product
Markonikov
Anti-Markonikov
what 2 functinoal groups are created in an epoxide ring opening?
2 OH groups
Hyperconjugation definition
delocalization of Pi electrons, increases stability
Hydroboration-Oxidation reactants
1.) BH3/THF
2.) H2O2, NaOH
What is the solvent for alkyne dihalogenation?
Note: NOT reactant
CCl4
What is the solvent for alkene dihalogenation?
Note: NOT reactant
CCl4
