Chapter 6 Flashcards
Acid catalyze addition of an alcohol
Hydrogen goes to a carbon, the rest goes to the other carbon, same as addition of water
Ether
R-O-R
Rearrangement
Tertiary carbocation are more stable, so prioritized and produce a surprise product that is major
Can only shift hydrogens and alkyl group 1 bond away
Ex: 1,2-Hydride shift (doesn’t have to be carbon 1 to 2, just means shift to next carbon)
If changes from a ring to a bigger ring will deminish angle strain
hydroboration-oxydation
BH3 Electrophile
Flat molecule with empty p orbital waiting for electrons
When added to reaction, gives the antimarkovnikov product
OH added where most hydrogens
H added where least hydrogens
No rearrangements
1.BH3/THF
2. HO-, H2O2, H2O
Addition Br2 or Cl2
Each Br or Cl goes to a carbon
Vicinal dibromide or dichloride (dihalide)
Produces cyclic bromonium ion as an intermediate
Product are initially anti and will rotate (if single bond) because second halide comes from the opposite side of the one in the cyclic
called an anti addition
If in a ring (ex cyclopentane) then doesn’t rotate, stays anti, always trans
No rearrangement because cyclic bromonium ion is not a carbocation
Addition I2
Alkenes do not add I2, product unstable, equilibrium lies to the left
Conversion of alkenes to vicinal halohydrins
Anti addition
Addition of halogen and something with OH (ex water)
Halohydrin formation
Br and ROH are anti, so trans, (wedges and dash)
Oxygen goes to place with less hydrogen, even if it causes steric hynderance
X goes to place with most hydrogens (less alkyl group)
In transition state, bond breaking which is making carbon more positive is quicker than bond forming with O, so carbon better at stebalizing this positive charge is the one with the most alkyl groups
Transition state
Up in the G graph
Show bonds breaking and forming as dashed lines
Ozonolysis of alkene
Produces ozonide
O3
Splits molecule in half with each an oxygen and a double bond between oxygen and carbon
Stereoselective
Solution is selective of a stereoisomer
Can be not stereoseletctive if X can go equally up and down on the planar molecule
If the reactant does not have an asymmetric center and the reaction forms a product with an asymmetric center, the product will be a racemic mixture.
If the reactant has an asymmetric center and the reaction forms a product with a new asymmetric center, the product will be a pair of diastereomers.
X will come for place with less substrates (if CH3 dashed, then X will be wedged)
Will produce syn (same side) or anti (opposite side)
Syn addition to trans and trans isomers
Trans: threo Fischer projection (same groups on opposite sides)
Cis: erythryo Fischer projection (same groups same side)
Cis anti threo can change 2 but not 1 or 3
