Chem Electrophilic Addition Reactions

addition of HX to an alkene

2 step

carbocation intermediate

markovnikov

can be syn or anti

addition of HX to an alkyne

addition of HX twice

pi complex intermediate, then carbocation intermediate

markovnikov for terminal, internal is less selective, symmetrical doesn’t matter

syn or anti, doesn’t really apply

H2O cat. H2SO4 to an alkene

yields an alcohol

carbocation intermediate

markovnikov, first H comes from acid

syn or anti

H2O bonds to C all together then gets deprotonated

H2O cat. H2SO4 to an alkyne

yields an enol which tautomerizes to a ketone (int) or aldehyde (term)

carbocation intermediate

can be markovnikov (term), doesn’t select for int

syn/anti don’t apply bc tautomerization

CH3OH cat. H2SO4 to an alkene

yields ether

carbocation intermediate

markovnikov

like addt of H2O, first H comes from acid, then CH3OH adds, then it gets deprotonated back to aci

X2 (usually Br2 or Cl2), CHCl2 to an alkene

yields 2 X atoms on adjacent Cs (“vincinal di____ides”)

CHCl2 doesn’t participate, it is just a solvent that dissolves X2

X cyclic triangle intermediate

anti

X2 (usually Br2 or Cl2), CHCl2 to an alkyne

same as alkenes, just happens twice if there’s enough X2

X2, H2O to an alkene

yields X attached to one C, OH on the other (“halohydrin”)

3 steps

• formation of cyclic triangle intermediate

• addition of water to most substituted C

• Deprotonation of water

anti addition

X2, CH3OH to an alkene

yields X on least sub C, OCH3 on more sub

3 steps:

• cyclic X intermediate

• attack by CH3OH to more sub

• deprotonation of CH3OH

anti addition

NaNH2 to an alkene

doesn’t do anything!

NaNH2 to an alkyne

deprotonates

mCPBA (peroxyacid) to an alkene

yields epoxide (cyclic triangle ether)

concerted

syn

maintains reactant stereochemistry

O3 to an alkene

yields an aldehyde (if there is an O-C-H bond anywhere) or a ketone (if it is O-C-R bonds)

1. BH3

2. H2O2, NaOH, H2O

to an alkene

yields antimarkovnikov alcohol

2 steps

• H of BH3 adds to more sub C and BH2 adds to less sub C

• BH2 gets replaced with OH

Syn

1. BH3

2. H2O2, NaOH, H2O

yields an aldehyde (term) or ketone (int)

antimarkovnikov

syn first step - H to most sub, BH2 to least

second step - replacement with OH and tautomerization

H2, Pd/C to alkenes

yields alkane

syn

kind of concerted bc catalyzed by metal but shouldn’t be any qs abt this.

H2, Pd/C to alkyne

yields alkane

syn

H2, Lindlar’s catalyst to alkyne

yields cis alkene

syn

NH3 (liq), Na to alkyne

yields trans alkene

anti