Vollhardt  Capítulo 8 (Álcoois)
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Vollhardt Capítulo 8 (Álcoois)


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a p t e r I n t e g r a t i o n P r o b l e m s
322 C h a p t e r 8 H y d r o x y F u n c t i o n a l G r o u p : A l c o h o l s
We now combine the two balanced half-reactions by adding them to each other, that is, (3) 1 (2), a 
procedure that cancels out the electrons to give equation (4).
 6 H
\ufffd 6 e3 RCH2OH \ufffd\ufffd3 RCH
O
B
 (3)
 14 H1 1 Cr2O7
22 1 6 e uuy 2 Cr31 1 7 H2O (2)
 3 RCH \ufffd 6 H
\ufffd
 \ufffd 2 Cr3\ufffd \ufffd 7 H2O3 RCH2OH \ufffd 14 H\ufffd \ufffd Cr2O72\ufffd
O
B
 (4)
In this form, (4) contains H1 on both sides. We can simplify it by removing the \u201cexcess\u201d H1 to 
furnish equation (5).
 2 Cr
3\ufffd8 H\ufffd Cr2O72\ufffd 7 H2O3 RCH2OH \ufffd\ufffd3 RCH
O
B
\ufffd\ufffd (5)
Finally, we add nonreacting \u201cspectator ions\u201d of this reaction to show the proper stoichiometry in 
equation (6).
 Cr2(SO4)3Na2Cr2O74 H2SO4 7 H2O3 RCH2OH \ufffd\ufffd Na2SO4\ufffd3 RCH
O
B
\ufffd\ufffd (6)
The balanced equation (6) very nicely reveals why the reaction is run in acidic medium: H2SO4 is 
consumed. It also highlights the oxidizing power of dichromate: One mole is suffi cient to effect the 
oxidation of three moles of alcohol.
New Reactions
1. Acid-Base Properties of Alcohols (Section 8-3)
OR ROH RO\ufffd
\ufffd
BH
Alkyloxonium ion
\ufffdO
H
H
H\ufffd
G
D Base B\ufffd
Alcohol Alkoxide
 Acidity: RO \u2013 H < HO \u2013 H . H2N \u2013 H . H3C \u2013 H
 Basicity: RO2 < HO2 , H2N2 , H3C2
Laboratory Preparation of Alcohols
2. Nucleophilic Displacement of Halides and Other Leaving Groups by Hydroxide (Section 8-5)
RCH2X RCH2OHHO\ufffd\ufffd X\ufffd\ufffd
H2O
SN2
X \ufffd halide, sulfonate
Primary, secondary (tertiary undergoes elimination)
A
B
RCHX RCHOCCH3CH3CO\ufffd
O
B
O
R\ufffd
A
RCHOH
R\ufffd
A
R\ufffd
\ufffd
SN2
HO\ufffd
Ester hydrolysis
A
A
R\ufffdCX
R
R\ufffd
A
A
R\ufffdCOH
R
R\ufffd
H2O, acetone
SN1
Best method for tertiary
 C h a p t e r 8 323
3. Reduction of Aldehydes and Ketones by Hydrides (Section 8-6)
B
RCH RCH2OH
O
NaBH4, CH3CH2OH B
RCR\ufffd
O
NaBH4, CH3CH2OH A
A
RCR\ufffd
OH
H
B
RCH
Aldehyde Primary
alcohol
RCH2OH
O 1. LiAlH4, (CH3CH2)2O
2. H\ufffd, H2O
Ketone Secondary
alcohol
1. LiAlH4, (CH3CH2)2O
2. H\ufffd, H2OB
RCR\ufffd
O
A
A
RCR\ufffd
OH
H
Oxidation of Alcohols
4. Chromium Reagents (Section 8-6)
B
RCH
AldehydePrimary alcohol
RCH2OH
O
PCC, CH2Cl2
KetoneSecondary alcohol
Na2Cr2O7, H2SO4 B
RCR\ufffd
O
A
RCHR\ufffd
OH
Organometallic Reagents
5. Reaction of Metals with Haloalkanes (Section 8-7)
RX Li RLi
Alkyllithium reagent
\ufffd
(CH3CH2)2O
RX Mg RMgX
Grignard reagent
\ufffd
(CH3CH2)2O
R cannot contain acidic groups such as O \u2013 H or electrophilic groups such as C\u201cO.
6. Hydrolysis (Section 8-7)
RLi or RMgX RHH2O\ufffd
RLi or RMgX RDD2O\ufffd
7. Reaction of Organometallic Compounds to Aldehydes and Ketones (Section 8-8)
RLi or RMgX RCH2OHCH2 O
Primary alcoholFormaldehyde
\ufffd P
R\ufffdCH
O
Secondary alcoholAldehyde
B A
A
RCR\ufffd
OH
H
RLi or RMgX \ufffd
R\ufffdCR\ufffd
O
Tertiary alcoholKetone
B A
A
RCR\ufffd
OH
R\ufffd
RLi or RMgX \ufffd
 Aldehyde or ketone cannot contain other groups that react with 
 organometallic reagents such as O \u2013 H or other C\u201cO groups.
8. Alkanes from Haloalkanes and Lithium Aluminum Hydride (Section 8-7)
RX LiAlH4\ufffd RH
(CH3CH2)2O
C h a p t e r I n t e g r a t i o n P r o b l e m s
Preparation of Alcohols section number
&
B
O
OsO4,
H2O2
1. RCOOH
2. H\ufffd, H2O
H2O,
cat. H\ufffd or HO\ufffd
R\ufffdOH,
cat. H\ufffd or HO\ufffd R\ufffd NH2 HCN HO
\ufffd H2O, HO\ufffd LiAlH4 H2O, H\ufffd or HO\ufffd R\ufffdMgBr LiAlH4
X\ufffdcat.
\ufffd
N
R
S
HO\ufffd, SN2
HO\ufffd, SN2
or
H2O, SN1
or
H2O, SN1
NaBH4
or
LiAlH4
R\ufffdMgX
or
R\ufffdLi 
HX H
\ufffd
, H2O,
deprotection H
\ufffd
, H2O
\ufffdNu
or
NuH
1. Hg(OCCH3)2
2. NaBH4
O
B
1. CH3CO2\ufffdNa\ufffd
2. HO\ufffd, H2O
Other
product:
RX
Other
product:
C(CH3)2CH2P
Product:
OH
Nu
12-10
17-6 17-7 17-9 17-11 18-5 18-9 19-11 20-4 20-4 20-4 23-4
12-78-5 8-5 8-5 8-6 9-8 9-8 9-9 12-48-8
C OH
i
{ O
ROC(CH3)3RCH2X RCHX
R\ufffd
A
RCX
R\ufffd
A
A
R\ufffd ROR
O
RCH(R\ufffd)
B
O
RCH(R\ufffd)
B O
C CG
D
G
D
P C CG
D
G
D
P
RCH(R\ufffd)
O
B
RCH(R\ufffd)
O
B
RCH(R\ufffd)
O
B
RCH(R\ufffd)
O
B
RCH2CH(R\ufffd)
O
B
RCOH
O
B
CHCRCH2
O
B
P
O
B
RCOR\ufffd
O
B
RCOR\ufffd
O
B
RCOR\ufffd
O
B
RCH
C CG
D
G
D
P
C CG
D
G
D
P
Product:
Aldol
RCH2C CHCH(R\ufffd)
H(R\ufffd)
OH
A
R O
A
A
O
B
HOCH2CH2CR
Other
product:
RCOH
O
B
Product:
Hemiacetal
R\ufffdO
Product:
Hydrate
OH
R H(R\ufffd)
HO
C
G
D
G
D
OH
R H(R\ufffd)
C
G
D
G
D
Product:
OH
R H(R\ufffd)
C
G
D
G
D
Vicinal diol
G
@ &
Product:
Product:
G@&
O
OH
HO OH
C
&
C
G
@
OC
HO
G
C
(
C
Vicinal diol
Hemiaminal
R\ufffdNH
Product:
OH
R H(R\ufffd)
C
G
D
G
D
Cyanohydrin
NC
A
A
H
R\ufffdCOH
R\ufffd
Product:
A
A
B
HO
RCCR
OH
Product:Product:
O
B
&
ð 1. BH3
2. H2O2, HO\ufffd
12-8
C CG
D
G
D
P
X2, H2O
Product:
G
G@&
O
X
OH
C C
(
C
12-6
C CG
D
G
D
P
12-11
3
2
4
Reactions of Alkyllithium and Grignard Reagents section number
R\u2013H
(R\u2013D) RCH2OH H
OH
R\ufffd R C
A
A
OO
R\ufffd 
OH
R\ufffd R C
A
A
OO
R\ufffdC Cðq
O
G
G D
D
PC C
C
A
\ufffd
RCHPP(C6H5)3
O O O
A
A
A
A
R C C C
OH
J
G
RCOH
B
O
R\ufffd C R
R
OH
O O
A
A
R\ufffdCR
B
O
R\ufffdCR
B
O R2Nð ðCHR
\ufffd
ð
\ufffd
SS
N R
N
SS
(RLi)
R2NHR\ufffdCqN
GD
G GD
PC C
C
CuI, O
B
CO2 B
CuI,
 O
R\ufffdCCl 
B
R\ufffdCOR\ufffd 
ORCH2P(C6H5)3
(RLi)
\ufffd
(RLi)
CH2R\ufffd
H2O
(or D2O) H2CPO R\ufffdCH
B
O
R\ufffdCR\ufffd
B
O
R\ufffdOH R\ufffdCqCH
G
G
G
D G
D
D
PC C
C
H
(RLi)
R\ufffd
O
R R\ufffd
OH
R\ufffdO\ufffd M\ufffd \ufffd M\ufffd
\ufffd M\ufffd
RLi or RMgBr
8-7 8-8 8-8 8-8 9-1 9-9 13-3 14-4 15-8
17-12 18-10 19-6 20-2 20-4 20-8 21-4 22-1 23-5 25-6
ð
\ufffd
3
2
5
326 C h a p t e r 8 H y d r o x y F u n c t i o n a l G r o u p : A l c o h o l s
Important Concepts
1. Alcohols are alkanols in IUPAC nomenclature. The stem containing the functional group gives 
the alcohol its name. Alkyl and halo substituents are added as prefi xes.
2. Like water, alcohols have a polarized and short O \u2013 H bond. The hydroxy group is hydrophilic 
and enters into hydrogen bonding. Consequently, alcohols have unusually high boiling points 
and, in many cases, appreciable water solubility. The alkyl part of the molecule is hydrophobic.
3. Again like water, alcohols are amphoteric: They are both acidic and basic. Complete deprot-
onation to an alkoxide takes place with bases whose conjugate acids are considerably weaker 
than the alcohol. Protonation gives an alkyloxonium ion. In solution, the order of acidity is 
primary . secondary . tertiary alcohol. Electron-withdrawing substituents increase the acidity 
(and reduce the basicity).
4. The conversion of the electrophilic alkyl group in a haloalkane, Cd1 \u2013 Xd2, into its nucleophilic 
analog in an organometallic compound, Cd \u2013 Md1, is an example of reverse polarization.
5. The carbon atom in the carbonyl group, C P O, of an aldehyde or a ketone is electrophilic and 
therefore subject to attack by nucleophiles, such as hydride in hydride reagents or alkyl in 
organometallic compounds. Subsequent to aqueous work-up, the products of such transformations 
are alcohols.
6. The oxidation of alcohols to aldehydes and ketones by chromium(VI) reagents opens up important 
synthetic possibilities based on further reactions with organometallic reagents.
7. Retrosynthetic analysis aids in planning the synthesis of complex organic molecules by identifying 
strategic bonds that may be constructed in an effi cient sequence of reactions.
Problems
24. Name the following alcohols according to the IUPAC nomenclature system. Indicate stereochem-
istry (if any) and label the hydroxy groups as primary, secondary, or tertiary.
(a) CH3CH2CHCH3
OH
A
 (b) CH3CHCH2CHCH2CH3
Br
A
OH
A
 (c) HOCH2CH(CH2CH2CH3)2
(d) 
C
H3C
CH2Cl
H
OH
A
; G^
 (e) 
CH2CH3
OH/\u2211
 (f) 
OH
Br
[
~ (g) C(CH2OH)4
(h) 
H OH
CH2OH
CH2OH
H OH
 (i) 
]
-
OH
CH2CH2OH
 ( j) ClH3C
CH2OH
CH2CH3
25. Draw the structures of the following alcohols. (a) 2-(Trimethylsilyl)ethanol; (b) 1-methylcyclopropanol; 
(c) 3-(1-methylethyl)-2-hexanol; (d) (R)-2-pentanol; (e) 3,3-dibromocyclohexanol.
26. Rank each group of compounds in order of increasing boiling point. (a) Cyclohexane, cyclohexanol, 
chlorocyclohexane; (b) 2,3-dimethyl-2-pentanol, 2-methyl-2-hexanol, 2-heptanol.
27. Explain the order of water solubilities for the compounds in each of the following groups. 
(a) Ethanol . chloroethane . ethane; (b) methanol