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Preparation of AlcoholsAlcohols can be formed from many, many different sources. More than 7

different functional groups can be converted to an alcohol.

R C

O

O H

R C

O

O R'

R COR

R'

O R'

RCH CH2

R2C CR2

OHHO

E, FDCB

ADiols

Carboxylic Acids

KetonesAldehydes

Alkyl HalidesRX

Ethers

Alkenes

Esters

AlcoholsROH

R

OEpoxides

G

H

Legend:

A: Substitution only. Hydroxide nucleophile; difficult reaction because of competing elimination (E2).See Carey Chpt. 8.

B: Hydration can go in two ways to give different regioselectivities. Oxymercuration-demercuration givesMarkovnikov product, hydroboration/oxidation gives opposite. Generally clean and high-yielding.Carey 6.10-11.Diols ("vicinal" diols) also can be formed by two complementary sequences. Hydroxylation (KMnO4or OsO4 with reductive cleavage) yields vicinal diols with syn addition (Carey 15.5). Epoxidation

followed by cleavage (peracid, then acid or basic cleavage) yields anti- or trans addition.C: Benzyl ethers can be cleaved by hydrogenolysis (H2/Pt or Pd) to give the alcohol.

R OCH2

R OCH2H

H+

H2

Pt or Pd

D: Addition of hydride reagents (LiAlH4, or NaBH4) or organometallic reagents (RMgBr or R-Li) yield

alcohols. The process converts the carbonyl carbon to a carbinol carbon (1 from reduction ofaldehyde; 2 from reduction of ketone or alkylation of aldehyde; 3 from alkylation of ketone). Carey15.2.

E: Addition of hydride reagents (LiAlH4, or NaBH4) or organometallic reagents (RMgBr or R-Li) yield

alcohols. Attack of the nucleophile is usually on the less hindered carbon, and trans geometryusually is seen. Carey 15.4.

F : Hydroxide attacks the less hindered carbon to give the trans diol. Carey 16.12-13.G: Alcohols are formed by the use of hydride reagents: LiAlH4, BH3. NaBH4 doesn't work (not

reactive enough), even though BH3 does. Go figure. Carey Table 15.3.

H: Two ways to do this, depending on which part of theester should yield the alcohol. First, simplehydrolysis of an ester gives an alcohol and an acid.

Second, reduction of an ester gives two alcoholproducts. Often, with simple esters, one of thealcohols is small, water soluble or volatile, and canbe separated easily from the other (Carey Table15.3.):

R C

O

O R'R CH2 O H HO R'+

R

CO O

R'

R

CO O

H

HO R'+

H2

O

H+ or OH-

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Hydration of Alkenes

CH3

CH3

CH3

H

H

H

H

BR2

OH

HgOAc

CH3

CH3

H

H

H

OH

OH

H

Hg(OAc)2

H2O

BH3

THF

H2O2

NaOH

NaBH4

Hydroxylation of Alkenes

CH3

CH3

O

O

Os

O

O

H

H

CH3

OH

OH

H

CH3

H

O

CH3

H

OH

OH

OsO4

Pyridine

NaHSO3

H2O

Basic KMnO4

RCO3H

CH2Cl2

NaOH

H2O

Reduction of Carbonyl Compounds

H3C

CH

H3C

H2C

CH2

OH

H3C

CH

H3C

H2C

CH

O

O

OH

C

O

O CH3

H2C OH

HO CH3

H3C(H2C)8 C

O

OH

H3C(H2C)8 CH2

OH+

NaBH4

CH3OH

NaBH4

CH3OH

LiAlH4

ether

LiAlH4

ether

Aldehydes Ketones Esters Carboxylic Acids