Addition Reactions (markovnikov/anti-markovnikov and syn/anti)

HX

(hydrohalogenation) markovnikov addition of H and X

- racemic mixture of enantiomers

HBr / ROOR

(hydrohalogenation) anti-markovnikov addition of H and Br

H₃O⁺

or

1)Hg(OAc)₂ / H₂O

2)NaBH₄

(acid catalyzed hydration/oxymercuration-demercuration) markovnikov addition of OH

- in dilute acid addition is favored

- in concentrated acid elimination is favored

- in 1)Hg(OAc)₂ / H₂O 2)NaBH₄, high yield is obtained

1) BH₃∙THF

2) H₂O₂ / NaOH

(hydroboration-oxidation) anti-markovnikov addition of OH

- syn addition (NOT anti position); only two of the four enantiomers are formed

H₂ / Pt

(hydrogenation) syn addition of two H's

- syn addition (NOT anti position); only two of the four enantiomers are formed

Br₂ / CHCl₃

(bromination) anti addition of two Br's (it can also be another halogen like I or Cl)

Br₂ / H₂O (HOR to add OR group)

(halohydrin formation) anti addition of Br (or Cl or I) and OH (OH goes to more substituted position)

- H₂O --> Br₂ and OH

- CH₃OH --> Br and OCH₃

- C₂H₅OH --> Br and OC₂H₅

- CH₃SH --> Br and SCH₃

1) RCO₃H or MCPBA

2) H₃O⁺

(anti dihydroxylation) anti addition of two OH's

1) OsO₄

2) NaHSO₃ / H₂O

or

KMnO₄ / NaOH

(syn dihydroxylation) syn addition of two OH's

- OsO₄ gives very high yield product but its toxic

- KMnO₄ gives medium yields but is non-toxic

1) O₃

2) DMS

(ozonolysis/oxidative cleavage) breaks all double bonds and binds O to previously double bonded carbons

markovnikov rule

the h atoms in the addition reaction go to the c with the most substituents

anti-markovnikov rule

the h atoms in the addition reaction go to the c with the least substituents

high T

favors elimination

low T

favors addition

mechanism: hydrohalogenation

HX

mechanism: acid-catalyzed hydration

H₃O⁺

1) Hg(OAc)₂, H₂O

2) NaBH₄

TSCL / Pyridine

changes OH group to OTs which is a better leaving group

concentrated H₂SO₄

easily and efficiently eliminates OH group

- acts like a small base

r configuration

clockwise

s configuration

counterclockwise

tert butyl

isopropyl