orgo ch9

Electrophilic addition reaction

Alkene are electron rich cause of pi e and react with electrophiles

Carbocation stability

Tertiary greater than secondary greater than primary benzylic tertiary greater than secondary greater than primary allylic

Carbocations undergo rearrangement

Hybrid shift, alkyl shift, ring expansion

Alkene——> hbr, or hcl, or hi

form carbocation intermediate, reaction is regioselective

alkene ——> H2O, H+ or H2O,H2SO4

form oh, form carbocation intermediate, regioselective and reversible reaction

alkene—→ OH, H+

form ether, form carbocation intermediate, regioselective reaction

Stereochemistry of addition of hcl, hbr, or hi, add h2o with h3o or h2so4, and add oh with h plus

Reactions neither stereoselective or stereospecific, stereo center produce pair of enantiomers, if chiral center then pair of diastereomers form

Alkene—→ 1. Hg(OAc)2, H2O, THF, 2. NaBH4

form alcohol, reduce with nabh4, form cyclic intermediate, regioselective

Alkene——> 1. Hg(OAc)2, ROH, THF, 2. NaBH4

form ether, reduce with nabh4, form cyclic intermediate, regioselective

Alkene——> 1. BH3, THF, 2. H2O2, NaOH, H2O

form oh, oxidation by h2o2, naoh, and h2o, square intermediate, product is cis form enantiomers, product is trans form diastereomers

Alkene ——>Br2,CH2Cl2 or Cl2,CH2Cl2

form cyclic intermediate, regioselective, stereoselective form pair of enantiomers, chiral form one product

Alkene——> Br2 or Cl2 stereospecific

cis form pair of enantiomers, trans form meso compound

alkynes —→ HBr or HCl

form carbocation intermediate, regioselective for terminal alkyne, have excess reaction

alkynes —→ Br2 or Cl2

forms cyclic intermediate, have excess reaction

alkynes —→ add 1. HgSO4, H2O, H2SO4 OR PtCl2, H2O

form ketone via keto enol tautomerism, acid catalyzed mechanism where terminal alkyne form methyl ketones and internal alkynes form ketones

alkynes —→ 1.(Sia)2BH or 9-BBN-H or catecholborane, THF, 2. H2O2, NaOH, H2O

forms aldehydes in basic condition via keto enol tautomerism, not regioselective

Reaction of C-C bond: add h2so4 with alkene

form dimer, trimers, polymers, form carbocation intermediate

Electrophilic addition

used for ring formation, new intramolecular form of cc bond

carbene

neutral intermediate, c with 6 e cause e deficient they are highly reactive electrophile

Alkenes: Simmons Smith reaction
—→ CH2I2, ZnCu or (CF3COO)Zn-CH2-I, CH2CL2

one step reaction, no change in stereochem, forms cyclopropane derivative

Alkenes —→ CHCl3, OH-, or CHCl3, t-BuO-

forms trichloromethyl anion, stereospecific reaction