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Chapter 8
of Alcohols and
Phenols
Structure of Alcohols
 Alcohols
are simply organic derivatives
of water formed by replacing one H of
water with an R group.
 All alcohols have the hydroxyl (OH)
functional group
Classification of Alcohols
 Alcohols
are classified as primary,
secondary, tertiary or aromatic
depending upon the class of the alcoholic
carbon
 Primary: carbon with –OH (alcoholic
carbon) is bonded to one other carbon.
 Secondary: carbon with –OH is bonded to
two other carbons.
 Tertiary: carbon with –OH is bonded to
three other carbons.
 Aromatic Alcohol (phenol): -OH is bonded
to a benzene ring.
Classify these:
C H3
C H3
CH
C H3
C H 2O H
C H3
C
OH
C H3
OH
OH
C H3
CH
C H2C H3
=>
IUPAC Nomenclature
 Find
the longest carbon chain
containing the carbon with the -OH
group.
 Drop the -e from the alkane name,
add -ol.
 Number the chain, starting from the
end closest to the -OH group.
 Number and name all substituents.
=>
Name these:
C H3
C H3
CH
C H 2O H
2-methyl-1-propanol
OH
C H3
CH
C H2C H3
2-butanol
C H3
C H3
C
OH
OH
C H3
2-methyl-2-propanol
Br
C H3
3-bromo-3-methylcyclohexanol
=>
Naming Diols
Two numbers are needed to locate the two
-OH groups.
 Use -diol as suffix instead of -ol.

OH
HO
1,6-hexanediol
=>
Glycols
1, 2 diols (vicinal diols) are called glycols.
 Common names for glycols use the name
of the alkene from which they were made.

C H 2C H 2
C H2C H2C H3
OH OH
OH OH
1,2-ethanediol
1,2-propanediol
ethylene glycol
propylene glycol
=>
Naming Phenols (Aromatic
Alcohols)
-OH group is assumed to be on carbon 1.
 For common names of disubstituted phenols,
use ortho- for 1,2; meta- for 1,3; and parafor 1,4.
 Methyl phenols are cresols.

OH
OH
H 3C
Cl
3-chlorophenol
meta-chlorophenol
4-methylphenol
para-cresol
=>
Physical Properties
 Unusually
high boiling points due to
hydrogen bonding between
molecules.
 Small alcohols are miscible in water,
but solubility decreases as the size of
the alkyl group increases.
=>
The High Boiling Points of Alcohols
and Phenols are due to their ability to
Hydrogen Bond to one another

Alcohols and phenols have much higher
boiling points than other molecules of
similar Molecular Weight
Alcohols Form Hydrogen Bonds



A positively polarized OH hydrogen atom from one
molecule is attracted to a lone pair of electrons on a
negatively polarized oxygen atom of another molecule
This produces a force that holds the two molecules
together
These intermolecular attractions are present in solution
but not in the gas phase, thus elevating the boiling
point of the solution
Solubility in Water
Polar
Non-polar
Solubility decreases as the size
of the alkyl group increases.
=>
Alchols and Phenols are
Weak Brønsted Acids
 Remember,
Bronsted Acids are Proton
Donars. Alcohols and Phenols can donate
a proton to water
 The products are H3O+ and an alkoxide
anion, RO, or a phenoxide anion,
ArO
Relative Acidities of Alcohols and Steric Effects
Alkyl groups make an alkoxide anion more
difficult to be solvated and stabilized by water
molecules and therefore make its formation less
likely and the corresponding acid necessarily
weaker
 The more easily the alkoxide ion is solvated by
water the more stable it is and the more its
formation is energetically favored

More likely to
form
Less likely to
form
Inductive Effects

Electron-withdrawing groups make an
alcohol a stronger acid by stabilizing the
alkoxide anion
Table of Ka Values
C H3
OH
=>
Generating Alkoxides from
Alcohols
As weak acids, alcohols react with strong
bases like sodium or potassium metal to
generate alkoxides
 Alkoxides are bases used as reagents in
organic chemistry

Formation of Phenoxide Ion
Phenol is more acidic than regular alcohols because
the phenoxide anion is resonance stabilized.
Electron withdrawing groups stabilize the
phenoxide anion and make phenol more acidic
Consequently, phenol can be deprotonated by a
simple hydroxy base.
O
O H
+
pKa = 10
OH
+
HOH
pKa = 15.7
=>



Substituted Phenols
Can be more or less acidic than phenol itself.
Remember, the acidity of any alcohol is determined by
the stability of the alkoxide or phenoxide anion
produced. The more stable the anion produced the
more acidic the alcohol
An electron-withdrawing substituent makes a phenol
more acidic by delocalizing the negative charge on the
phenoxide anion
Phenols with an electron-donating substituent are less
acidic because these substituents concentrate the
charge
Preparation of Alchols: an
Overview
Alcohols are derived from many types of
compounds
 Also the alcohol hydroxyl can be converted into
many other functional groups
 This makes alcohols useful in synthesis

Review: Preparation of Alcohols from
Alkenes

Markovnikov and Anti-Mardovnikov
hydration
H2SO4
Alcohols from Reduction
of Carbonyl Compounds
Reduction of a carbonyl compound in
general gives an alcohol
 Note that organic reduction reactions
increase the C-H bonds and/or decrease
the C-O bonds

1.H-
2.H+
Reduction of Aldehydes and
Ketones

Aldehydes gives primary alcohols

Ketones gives secondary alcohols
1.H-
1.H-
2.H+
2.H+
Reducing agents: Sodium
Borohydride and Lithium Aluminum
Hydride, Sources of H-
NaBH4 is safe, not sensitive to moisture, and it
does not reduce other common functional
groups
 Lithium aluminum hydride (LiAlH4) is more
powerful, will reduce species that NaBH4 will
not, but is dangerous to use
 Both add the equivalent of “H-”

Mechanism of Reduction

The reagent adds the equivalent of
hydride to the carbon of C=O and
polarizes the group as well
Reduction of Carboxylic
Acids and Esters
Carboxylic acids and esters are reduced
to give primary alcohols
 LiAlH4 is used because NaBH4 is not
effective

Sodium Borohydride
 Hydride ion, H , attacks the
carbonyl carbon, forming an
alkoxide ion.
 Then the alkoxide ion is
protonated by dilute acid.
 Only reacts with carbonyl of
aldehyde or ketone, not with
carbonyls of esters or carboxylic
acids. O
H
H
O
C
H
C
H
H
H3O
+
O
C
H
=>
H
Lithium Aluminum
Hydride
 Stronger
reducing agent than
sodium borohydride, but dangerous
to work with.
 Converts esters and acids to 1º
alcohols.
O
H
C
OC H3
LAH
H3O
+
O
H
C
H
=>
LiAlH4 Reactions
with Esters and Carboxylate
Anions
 Use
two moles of Hydride (H-)
reagent.
 The product is a primary alcohol with
two hydrogens from hydride reagent.
 Reaction with the first mole of Hydride
reagent produces an aldehyde
intermediate, which reacts with the
second mole of Hydride
30
LiAlH4 and Ester – Step 1
• The first hydride (H-) attacks the carbonyl.
• Alkoxide ion leaves! ? !
C H3
H3C
C
RH- M g B r
H
R
O
C H3O
C
O
OC H3
MgB r
Alkoxide
C H3
MgB r
O
OC H3
C H3
H
R
C
H
R
OrO
+ + CH
M g3B
C H3
C
O
Aldehyde intermediate
=>
31
Second step of reaction
• The second hydride reacts with the aldehyde
intermediate to form an alkoxide ion.
• Alkoxide ion is protonated with water or dilute
acid.
C H3
C H3
R
HH-M- g B r
+
H
R
HR
C
O
C
O
MgB r
R
H
HOH
+
C H3
HR
C
H
R
H
OH
=>
32
Comparison of
Reducing Agents
LiAlH4 is stronger.
 LiAlH4 reduces
more stable
compounds which
are resistant to
reduction.

=>
Organometallic Reagents
 Carbon
is bonded to a metal (Mg)
 Carbon is more electronegative
than the metal and therefore is
nucleophilic (partially negative).
 It will attack a partially positive
carbon.
– C = O in much the same way as the
HA
new carbon-carbon bond forms
and a more complex alcohol is
formed.
34
Grignard Reagents
 Formula
+MgX)
R-Mg-X (reacts like R:-
 Stabilized
by anhydrous ether
 May be formed from any halide
– primary
– secondary
– tertiary
– vinyl
– aryl
=>
35
Some Grignard Reagent
Formations
Br
+
e th e r
Mg
Cl
M gC l
C H 3 C HC H 2 C H 3
C H3C
Br
MgB r
+
Mg
C H2
+
Mg
ether
e th e r
C H 3 C HC H 2 C H 3
C H3C
C H2
=>
MgB r
36
Reaction with Carbonyl
R:- attacks the partially positive carbon
in the carbonyl.
 The intermediate is an alkoxide ion.
 Addition of water or dilute acid
protonates the alkoxide to produce an
alcohol.

R
C
O
R
C
O
R
C
OH
HO H
OH
=>
37
Synthesis of 1° Alcohols
Grignard + formaldehyde yields a
primary alcohol with one additional
carbon.
H3C
C H3
H
C
C
H
C H2
C H3
H
C
MgB r
O
C H3
CH
H
C H2
C H2
H
O
MgB r
H
H
C H3
C H3
C
CH
H
C H2
C H2
C
HO H
O
H
H
=>
38
Synthesis of 2º Alcohols
Grignard + aldehyde yields a secondary
alcohol.
H3C
C H3
H
C
C
H
C H2
C H3
H3C
C
MgB r
O
C H3
CH
C H3
C H2
C H2
H
O
MgB r
H
H
C H3
C H3
C
CH
C H3
C H2
C H2
C
O
HOH
H
H
=>
39
Synthesis of 3º Alcohols
Grignard + ketone yields a tertiary
alcohol.
H3C
C H3
H
C
C
H
C H2
H
C H3
H3C
C
MgB r
O
C H3
CH
C H3
C H2
C H2
H3C
O
MgB r
C H3
C H3
C H3
C
CH
C H3
C H2
C H2
C
O
HOH
H
C H3
=>
40
How would you synthesize
these using a Grignard
Reagent…
OH
C H2OH
C H 3 C H 2 C HC H 2 C H 2 C H 3
OH
C H3
OH
C
C H3
C H2C H3
=>
41
Grignard Reactions
with Esters
 Use
two moles of Grignard attack. Just
as two moles of Hydride attacked an
Ester.
 The product is a tertiary alcohol with
two identical alkyl groups ( from
Grignard).
 Reaction with one mole of Grignard
reagent produces a ketone
intermediate, which reacts with the
second mole of Grignard reagent.
42
Grignard and Ester – First Step
 Grignard
attacks the carbonyl.
 Alkoxide ion leaves! ? !
C H3
H3C
R
C
MgB r
O
R
C
C H3O
C
O
OC H3
MgB r
OC H3
C H3
R
O
C H3
MgB r
R
+
C
M g B rO C H 3
O
Ketone intermediate
=>
43
Second step of reaction
Second mole of Grignard reacts with the ketone
intermediate to form an alkoxide ion.
Alkoxide ion is protonated with dilute acid.
C H3
C H3
R
MgB r
+
R
R
C
O
C
O
MgB r
R
HOH
C H3
R
C
R
OH
=>
44
How would you
synthesize...
Using an ester.
OH
C H3
C H3C H2C C H3
C
C H3
OH
OH
C H 3 C H 2 C HC H 2 C H 3
=>
45
Some Reactions of Alcohols

Two general classes of reaction
– At the carbon of the C–O bond
– At the proton of the O–H bond
Dehydration of Alcohols to Yield
Alkenes
The general reaction: forming an alkene
from an alcohol through loss of O-H and H
(hence dehydration) of the neighboring C–
H to give  bond
 Specific reagents are needed

Acid- Catalyzed Dehydration
Tertiary alcohols are readily dehydrated with
acid
 Secondary alcohols require more severe
conditions (75% H2SO4, 100°C) - sensitive
molecules don't survive
 Primary alcohols require very harsh conditions
– impractical
 Reactivity order is the result of the stability
order of the carbocation intermediate

Dehydration with POCl3
 Phosphorus
oxychloride in the
amine solvent pyridine can lead to
dehydration of secondary and
tertiary alcohols at low
temperatures
49
Conversion of Alcohols into
Alkyl Halides
3° alcohols are converted by HCl or HBr
at low temperature (Figure 17.7)
 1° and 2 ° alcohols are resistant to acid
– use SOCl2 or PBr3 by an SN2
mechanism

50
Oxidation of Alcohols
This can be accomplished by a wide range of
inorganic oxidizing agents, such as KMnO4,
CrO3, and Na2Cr2O7
 Remember oxidation in Organic Chem refers to
any reaction that adds bonds from carbon to
oxygen and/or removes bonds from carbon to
hydrogen

Oxidation of Primary
Alcohols
To aldehyde: pyridinium chlorochromate
(PCC) in dichloromethane
 Other reagents produce carboxylic acids

Oxidation of Secondary
Alcohols

Effective with inexpensive reagents
such as Na2Cr2O7 in acetic acid or CrO3
in H2SO4 (Jones Reagent)
Laboratory Preparation of
Phenols
From aromatic sulfonic acids by melting
with NaOH at high temperature
 Limited to the preparation of alkylsubstituted phenols

Reactions of Phenols
 Phenols
take part in electrophilic
aromatic substitution reactions.
 The OH group is an ortho para
activating group so phenol readily
substitute the following in the ortho
and para positions:
– Br using Br2/FeBr3
– NO2 using HNO3/H2SO4
– SO3H using SO3/H2SO4
1/--страниц
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