Advices For Studying Organic Chemistry

B B

H

syn addition

CH + enantiomer

3 anti-Markovnikov

H CH^3

H

11.7 ALCOHOLS FROM ALKENES THROUGH

HYDROBORATION-OXIDATION

1. Addition of the elements of water to a double bond can be achieved through
   hydroboration, followed by oxidation and hydorlysis of the organoboron
   intermediate to an alcohol and boric acid.

CH 3 CH CH 2 (CH 3 CH 2 CH 2 ) 3 CH 3 CH 2 CH 2

H 2 O 2 /OH OH

B

−

Propene Tripropylborane Propyl alcohol

(^3) Hydroboration Oxidation^3
THF:BH 3

A Mechanism for the Reaction

Oxidation of Trialkylboran

R B −B

R

R

+ R

R

R

B

R

R

R

Trialkyl-

borane

Hydroperoxide

ion

Unstable intermediate Borate ester

The boron atom accepts an electron

pair from the hydroperoxide ion to

form an unstable intermediate.

An alkyl group migrates from

boron to the adjacent oxygen

atom as a hydroxide ion depatrs.

−OOH O OH O + −OH

(^)

2. The alkylborane produced in the hydroboration, without isolation, are oxidized
   and hydrolyzed to alcohols in the same reaction vessel by the addition of
   hydrogen peroxide in aqueous base.