Alcohols and Phenols
1435-1436
2014-2015
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Alcohols and Phenols
Learning Objectives
Chapter six concerns alcohols and phenols and by the end of this chapter
the student will:
 know the difference in structure between alcohols and phenols
Know the different classes of alcohols
 Know how to name alcohols and phenols
 Know the physical properties (solubility, boiling and melting points)
 Know how hydrogen bonds are formed and its effect on boiling points
of alcohols
Know the acidic properties of alcohols and phenols
know the different methods that can be used to prepare alcohols and
phenols.
 Know the chemical reactions of these compounds ( some reactions are
review, others are extensions of the chemistry that will be discussed on
chapters 8, 9 & 10
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Alcohols and Phenols
Structure Of Alcohols and Phenols
 Alcohols and phenols may be viewed as organic derivatives of water.
Water
H-O-H R-O-H or PhCH2OH
Alcohol
Phenol
Ph-O-H
 Alcohols and phenols have a common functional group, the hydroxyl group,
—OH.
- In alcohols the hydroxyl group is attached to an alkyl group, —R.
- In phenols the hydroxyl function is directly attached to benzene ring
OH
OH
145 Chem.
Phenol
Benzyl alcohol
OH
Cyclohexanol
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Alcohols and Phenols
Classification and Nomenclature of Alcohols
Alcohols are classified according to the type of the carbon atom
connected to the hydroxyl group (carbinol carbon) into:
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Alcohols and Phenols
NOMENCLATURE OF ALCOHOLS
IUPAC Nomenclature Of Alcohols
Alcohols are named according to the following rules:
1.
Select the longest continuous carbon chain that contains the -OH group. Replace
the ending e of the alkane by the suffix –ol
2. If a molecule contains both an -OH group and a C=C or cΞc bond;
 Choose the chain that include both of them even if this is not the longest chain.
 The name should include suffixes indicate presence of both the OH group and the
unsaturated groups.
 The OH group takes precedence over the double or triple bonds in getting the
lower number.
 Cyclic alcohols are named using the prefix cyclo-, the carbon bearing the
hydroxyl group is assumed to take number 1.
3. The suffix diol is added to the name of the parent hydrocarbon when there are two
OH groups.
4. The suffix triol is added when there are three OH groups.
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Alcohols and Phenols
Common Nomenclature Of Alcohols
 List the names of alkyl substituents attached to the hydroxyl group, followed by the
word alcohol.
If two OH groups present on two adjacent carbons these known as glycols
Primary alcohols
CH3OH
CH3CH2OH
Common
Methyl alcohol
Ethyl alcohol
IUPAC
Methanol
Ethanol
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CH2=CHCH2OH
Allyl alcohol
2-Propen-1-ol
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Alcohols and Phenols
Secondary and tertiary alcohols
OH
OH
CH3
OH
Common Isopropyl alcohol
IUPAC
145 Chem.
2-Propanol
Cyclopentyl alcohol
Cyclopentanol
Methylcyclohexyl alcohol
1-Methyl-1-cyclohexanol
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Alcohols and Phenols
Examples
OH
OH
OH
1-Phenylmethanol
4-Methyl-2-cyclohexen-1-ol Benzyl alcohol (common name)
5
4
3
2
1
(CH3)2C=CHCH(OH)CH3
4- Methyl-3-penten-2-ol
145 Chem.
2-Phenylethanol
OH
OH
Cl
OH
4-Chloro-2-methyl-1-penten-3-o
Ethan-1,2-diol
Ethelene glycol (common name)
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Alcohols and Phenols
Examples
OH
OH
OH
But-3-en-2-ol
Pent-4-yn-1-ol
5-Ethyl-hex-5-en-3-ol
OH
OH
CH3
HO
145 Chem.
OH
OH
IUPAC
Ethane-1,2-diol
Propane-1,2-diol
or 1,2-Propanediol
Common
Ethylene glycol
Propylene glycol
OH
OH
Propane-1,2,3-triol
or 1,2,3,-Propantriol
Glycerol or Glycerin
Alcohols and Phenols
Physical Properties of Alcohols
1) Boiling Points of Alcohols
 The boiling points increase with increase in molecular weights.
• Alcohols have higher boiling points(b .p.) than alkanes of similar weight this is
due to the presence of hydrogen bonds between molecules of alcohols.
hydrogen bond
OH
>
OH
>
OH
>
Br
>
Melting & boiling points
Increases in this direction
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Alcohols and Phenols
2) Solubility Of Alcohols and Phenols
Alcohol and water contain hydroxyl group that can form hydrogen bonds.
 The hydroxyl group is hydrophilic “water loving”
 The alkyl group of alcohols is hydrophobic “ water hating”
 As the number of the –OH group in alcohol increases, the solubility in water
increases.
Diols and triols are more soluble in water than monohydroxyalcohols.
The lower alcohols are completely miscible with water
 As the number of carbons in the alcohol increases, the solubility in water
decreases.
Homework
H2C
H
C
CH2
OH
OH
IUPAC
Nomenclature
OH
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Commen
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Alcohols and Phenols
3) Acidic Properties of Alcohols:
Alcohols are very weak acids
The hydroxy proton of an alcohol is weakly acidic
A strong base can abstrate the hydroxyl proton to give an alkoxide ion.
R-O-H
B
R-O
CH3CH2OH
+ B-H
ClCH2CH2OH
CH3OH
15.5
PKa= 15.9
less acidic
15.3
most acidic
Electron-withdrawing group (-I) increase acidity
Electron-releasing group (+I) decrease acidity
Cl
Cl
Cl
OH
>
OH
>
OH
>
H3CO
OH
Cl
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Alcohols and Phenols
Synthesis (Preparation) of Alcohols
1- Hydration From Alkenes
H3O+
OH
+
major
1- Oxidation of Alkenes
minor
OH
OH
KMnO4
OH-/H2O
2- From alkyl halide
OH
cis glycol
alcohol,KOH
heat
H3C C CH2
H
(elimination of HX using
base gives alkene)
CH3CH2CH2Cl
dil OHor aq. KOH
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CH3CH2CH2OH
nucleophilic substitution
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Alcohols and Phenols
3- Reduction of aldehydes, ketones and carboxylic acids
O
H
LiAlH4
H
C
C CH3
3
CH3CCH3 or NaBH
4
OH
or H2/Pt
O CH MgBr
H
3
H3C C CH3
CH3CH
OMgBr
O
LiAlH4
CH3COH
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H3O+
H
H3C C CH3
OH
H2
H3C C OH
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Alcohols and Phenols
4- Addition of Grignard compounds to aldehydes & ketones
MgCl
O
CH3CCH3 +
OH
H3C C CH3
OMgCl
H3C C CH3
H3O+
Tertiary alcohol
Ketone
Secondary alcohol
l
Primary alcohol
Methanal
formaldehyde
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Alcohols and Phenols
Reaction of Alcohols
1. Dissociation of O-H Bond
Reaction as acids (Breaking of oxygen- Hydrogen bond CO ‫ـــــ‬H)
A. Formation of Salt (Alkoxide formation)
CH3CH2OH
Na
H2
H3C C ONa
Sodium ethoxide
B. Formation of Esters
H+
H+/ H2O
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Alcohols and Phenols
2. Dissociation of C-O Bond
Reaction with C‫ــــ‬OH bond cleavage
A. Elimination Reactions
CH3CH2OH
conc.H2SO4
H2C CH2
B. Substitution Reaction
CH3CH2OH
HCl/ ZnCl2
H3C CH2Cl
or SOCl2
or PCl3
or PCl5
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Alcohols and Phenols
C. Oxidation Reactions
CH3CH2OH
O
H3C CH
Cu /
or PCC
O
KMnO4
CH3CH2OH
OH
CH3CHCH3
H3C
Cu /
or KMnO4
or PCC
, CrO3. HCl
PCC =
C-OH
O
H3C C-CH3
Pridinium Chloro chromate
N
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Alcohols and Phenols
Nomenclature and acidity of Phenols
Phenols (compounds having hydroxyl group directly attached to a
benzene ring ) are generally named as derivatives of the simplest
member of the family, phenol
Acidity :
Alcohols and phenols have weak acidic properties.
Phenols are much stronger acids than alcohols.
Introduction of electron-withdrawing groups, such as NO2 or CN, on
the ring increases the acidity of phenols.
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Alcohols and Phenols
OH
OH
<
OH
OH
<
O2N
O2N
<
<
4-Methylphenol
p-Cresol (Common)
PH>10
Phenol
PH=10
OH
NO2
2,4-Dinitrophenol
4-Nitrophenol
PH=4
PH=7
OH
CHO
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Picric acid
2,4,6-Trinitrophenol
PH=0.25
OH
COOH
Cl
2-Hydroxybenzaldehyde
o-Hydroxybenzaldehyde
Salicylaldehyde
NO2
NO2
NO2
CH3
OH
2-Hydroxybenzoic acid
o-Hydroxybenzoic acid
Salicylic acid
NH2
3-Amino-5-chlorophenol
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Alcohols and Phenols
Synthesis of Phenols
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Alcohols and Phenols
Reactions Phenols
Ethers formation
O
CrO3 / H+
O
p-Benzoquinone
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Alcohols and Phenols
2. Electrophilic Substitution Reactions
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Alcohols and Phenols
Home Work
KMnO4
OH-/H2O
MgCl
O
HCH +
O
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H3O+
H2C MgBr
H3O+
+
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Alcohols and Phenols
4) The IUPAC name of
A) 4-Ethyl-5-heptyn-3-ol
B) 4-Ethyl-5-heptan-3-ol
C) 4-Ethyl-5-hepten-3-ol
D) 4-Etyl-2-hepten-5-ol
5) The IUPAC name of
A) 3-Methyl-1-bromocyclohexanol
B) 2-Bromo-3-methylcyclohexanol
C) 4-Bromo-2-methylcyclohexanol
D) 3-Bromo-1-methylcyclohxanol
is:
OH
is:
6) The most acidic compound is:
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Alcohols and Phenols
7) The common name of 2-methyl-2-propanol is:
A) Allyl alcohol
B) Isopropyl alcohol
C) tert-Butyl alcohol
D) Benzyl alcohol
8) The following reaction gives
A) 4-Ethylphenol
B) 2-Ethylphenol
C) Ethylphenyl ether
D) Ethylphenyl ketone
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Alcohols and Phenols
9) The major product for the following reaction is
10) The product of the reaction shown below is
11) Which of the following compounds has the highest boiling point?
Alcohols and Phenols
Thank You for your kind attention !
Questions?
Comments
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