Stereochemistry of Addition Reactions

Hydrogenation

• H₂ addition

• Syn addition

• Forms alkane

Hydrohalogenation

• HX addition

  • in inert solv: Markovnikov, C⁺

  • in peroxides: Anti-Markovnikov

• Not stereoselective

• Forms alkyl halide

Halogenation

• X₂ addition

• Anti addition

• Forms vicinal halide

Halohydrin Formation

• X + OH addition

• Anti addition

• Forms halohydrin

Hydration

• H + OH addition

  • in Hg++/H₂O or H₃O⁺: Markovnikov, C⁺, Not stereoselective

  • in Hg(OAc)₂ * H₂O / NaBH_4: Markovnikov, Anti addition

  • in BH₃ * THF / H₂O₂, NaOH: Anti-Markovnikov, Syn addition

Cyclopropanation

• Cyclopropane ring addition

  • in CH₂I₂ / Zn & Cu (Simmons-Smith reaction): Syn addition, no additional halides

  • in CHX₃ / strong base, bad nucleophile aka t-buO-: Syn addition, additional halides

Polar protic solvents

• Used for E₁, SN₁

• -OH, H₂O

Polar aprotic solvents

• Used for E₂, SN₂

• DMF, DMSO, CH3CN, HMPA

Nonpolar protic solvents

• Acetic acid

• t-butyl alcohol

Nonpolar aprotic donor solvents

• Used for Grignard reactions, organolithium reactions

• THF, Et-O-Et

Nonpolar aprotic nondonor solvents

• Used for carbenes, Simmons-Smith reaction, free radicals

• CH₂Cl₂, CHCl₃, CCl_4, alkanes