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Chapter 33
Hydroxy Compounds
33.1
33.2
33.3
33.4
33.5
33.6
33.7
33.8
1
Introduction
Nomenclature of Hydroxy Compounds
Physical Properties of Hydroxy Compounds
Acidic Properties of Hydroxy Compounds
Preparation of Hydroxy Compounds
Reactions of Alcohols
Reactions of Phenol
Uses of Alcohols
New Way Chemistry for Hong Kong A-Level Book 3A
33.1 Introduction (SB p.206)
Hydroxy compounds: Organic compounds with the
hydroxy group(s) (–OH) attached
to an alkyl group or aromatic ring
1. Alcohols
2
•
Compounds containing one or more –OH attached to an
alkyl group
•
General formula for alcohols with –OH group: CnH2n+1OH
e.g.
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33.1 Introduction (SB p.206)
• Depending on the number of alkyl groups attached to the
carbon which is bonded to the hydroxy group
• Alcohols can be classified as:
Primary alcohol
3
Secondary alcohol
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Tertiary alcohol
33.1 Introduction (SB p.207)
2. Phenols
•
Compounds that have a – OH group directly attached
to a benzene ring
•
General formula for phenols: Ar – OH
e.g.
4
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33.2 Nomenclature of Hydroxy Compounds (SB p.207)
Alcohols
1. Select the longest possible straight chain to which the
hydroxyl group is directly attached. Change the name of
the alkane correspending to this chain by dropping the
final ‘-e’ and adding the suffix ‘-ol’.
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2. Number the longest possible straight chain in such a
way so as to give the carbon atom bearing the hydroxyl
group the lower number.
3. Designate the position of the hydroxyl group by using
this number, and also the positions of other substituents
by using the numbers corresponding to their positions
along the carbon chain.
6
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33.2 Nomenclature of Hydroxy Compounds (SB p.207)
Examples:
7
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33.2 Nomenclature of Hydroxy Compounds (SB p.208)
Phenols
• Phenol will be the parent name when a benzene ring
containing a –OH group
• When substituents are present, the –OH group is assumed to
be in position 1, and numbers are assigned to the substituents
according to their positions in the benzene ring
e.g.
8
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33.2 Nomenclature of Hydroxy Compounds (SB p.208)
Example
33-1
Solution:
For each of(a)
the(i)following hydroxy compounds:
(i) Draw the complete structural formula.
(ii) Classify them as primary, secondary or tertiary
(ii) A secondary alcohol
alcohols.
(b) (i)
(a) Hexan-3-ol
(b) 3-Methylbutan-1-ol
(ii) A primary alcohol
(c) 2-Methylcyclopentanol
(c) (i)
(ii) A secondary alcohol
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Answer
33.2 Nomenclature of Hydroxy Compounds (SB p.209)
Check Point 33-1
(a) Draw(a)the structural formulae of all isomers of alcohols
having the molecular formula C4H10O. Give their
IUPAC names.
Answer
10
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33.2 Nomenclature of Hydroxy Compounds (SB p.209)
Check Point 33-1
(b) Draw the structural formulae of three isomeric
bromophenols with the molecular formula C6H4BrOH.
Give their IUPAC names.
Answer
(b)
4-Bromophenol
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New Way Chemistry for Hong Kong A-Level Book 3A
33.3 Physical Properties of Hydroxy Compounds (SB p.209)
Hydroxy
compound
Alcohols:
Methanol
Ethanol
Propan-1-ol
Butan-1-ol
Pentan-1-ol
Hexan-1-ol
Propan-2-ol
Methylpropan-1-ol
Butan-2-ol
Methylpropan-2-ol
Phenols:
Phenol
2-Methylphenol
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Formula
Boiling
Melting
Density at
point (°C) point (°C) 20°C (g cm–3)
CH3OH
CH3CH2OH
CH3(CH2)2OH
CH3(CH2)3OH
CH3(CH2)4OH
CH3(CH2)5OH
(CH3)2CHOH
(CH3)2CHCH2OH
CH3CH2CHOHCH3
(CH3)3COH
64.5
78.5
97.2
117
138
157
82.4
108
99.5
82.5
–97.7
–117
–127
–89.5
–78.8
–51.6
–89.5
–108
–115
25.5
0.791
0.789
0.803
0.810
0.814
0.814
0.785
0.802
0.808
0.786
C6H5OH
CH3C6H4OH
182
191
40.9
31.0
1.073
1.046
New Way Chemistry for Hong Kong A-Level Book 3A
33.3 Physical Properties of Hydroxy Compounds (SB p.210)
Boiling Point and Melting Point
Intermolecular hydrogen bonds
between alcohol molecules is
stronger than van der Waals’
forces between alkane
molecules
 alcohols have higher b.p.
and m.p.
13
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33.3 Physical Properties of Hydroxy Compounds (SB p.210)
Isomers of C4H9OH
Boiling
point (°C)
117
108
99.5
Branching of the carbon chain
reduces the surface area in
contact with other molecules
 Reduction in the extent of
intermolecular hydrogen
bonds that can be formed
between neighbouring
molecules
82.5
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33.3 Physical Properties of Hydroxy Compounds (SB p.211)
Density
• Simple alcohols are less dense than water at 20°C
• Phenols are slightly denser than water at 20°C
• The densities of alcohols increase with increasing
relative molecular masses
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33.3 Physical Properties of Hydroxy Compounds (SB p.211)
Solubility
• Alcohols with a relatively short carbon chain (e.g.
methanol, ethanol, propan-1-ol and propan-2-ol) are
completely miscible with water
• The solubility decreases as the hydrocarbon chain
increases
e.g. the solubility of butan-2-ol is 8 g per 100 g of water
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33.2 Nomenclature of Hydroxy Compounds (SB p.209)
Check Point 33-2
(a) Arrange the following compounds in order of increasing
boiling points:
(a)
Answer
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33.2 Nomenclature of Hydroxy Compounds (SB p.209)
Check Point 33-2
(b) Which member in each of the following pairs is more
soluble in water?
(i) CH3CH2OH or CH3CH2CH2CH2OH
(ii)
(b) (i) CH3CH2OH
(iii)
(ii)
(iii)
Answer
18
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33.4 Acidic Properties of Hydroxy Compounds (SB p.212)
• Alcohols are neutral
• Alcohols show acidic properties when reacting with
strong bases (e.g. sodium metal)
• The acidic property depends on the stability of the
alkoxide ion formed which is partly influenced by the
structure of the carbon chain
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33.4 Acidic Properties of Hydroxy Compounds (SB p.213)
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33.4 Acidic Properties of Hydroxy Compounds (SB p.213)
• 3° alkoxide ions are the least stable
21
∵
3 electron-releasing alkyl groups release
electrons to the negatively charged oxygen atom

3° alcohol is the least acidic
Hydroxy compound
pKa
Methanol
Ethanol
Methylpropan-2-ol
Phenol
2-Chlorophenol
2-Nitrophenol
2-Methylphenol
15.5
16
18
10.00
8.11
7.17
10.20
Phenols have smaller pKa
 stronger acids than alcohols
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33.4 Acidic Properties of Hydroxy Compounds (SB p.214)
• Phenols are more acidic than alcohols
∵
22
phenoxide ion is more stable than alkoxide ion due
to resonance stability (4 resonance structures can
be drawn)
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33.4 Acidic Properties of Hydroxy Compounds (SB p.214)
The negative charge disperses over the entire benzene ring
and oxygen atom by extended delocalized  electron cloud
 phenoxide ion is stabilized
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33.4 Acidic Properties of Hydroxy Compounds (SB p.214)
Phenol is acidic enough to react with NaOH but not Na2CO3
The order of acidity of some organic compounds and water:
Simple tests to distinguish alcohols, phenols, carboxylic acids
Sodium hydroxide
Sodium hydrogencarbonate
Alcohols
No reaction
Phenols
React to give salts and water
Carboxylic acids React to give salts and water
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No reaction
No reaction
CO2 evolved
33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
Example 33-2
Arrange the following compounds in order of increasing
acidity.
Solution:
The acidity of the compounds increases in the order:
Answer
25
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33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
Check Point 33-3
Which of the following compounds is more acidic? Explain
briefly.
(a) CF3CH2COH and CH3CH2OH
Answer
(a) CF3CH2OH is more acidic, because –CF3 is a strong
electron-withdrawing group. It exerts a negative inductive effect
on the conjugate base of CF3CH2OH (i.e. CF3CH2O–) and thus
stabilizes the CF3CH2O– ion.
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33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
Check Point 33-3
Which of the following compounds is more acidic? Explain
briefly.
(b)
(b)
is more acidic. The reason is that the conjugate
base is stabilized by the negative inductive and resonance
effects of the –NO2 group.
Answer
27
New Way Chemistry for Hong Kong A-Level Book 3A
33.5 Preparation of Hydroxy Compounds (SB p.216)
Preparation of Alcohols
Fermentation of Carbohydrates
amylase
2(C6H10O5)n + nH2O  nC12H22O11
60°C
maltase
C12H22O11 + H2O  2C6H12O6
15°C
zymase
C6H12O6 
2CH3CH2OH + 2CO2
15°C
The concentration of ethanol can be increased by
fractional distillation
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33.5 Preparation of Hydroxy Compounds (SB p.216)
Alkaline Hydrolysis of Haloalkanes
• Nucleophilic substitution reaction of haloalkanes
whereby 1°, 2° and 3° alcohols can be prepared
• The equilibrium lies towards the right
∵
29
OH– is a better nucleophile than halide ion
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33.5 Preparation of Hydroxy Compounds (SB p.216)
Reduction of Aldehydes and ketones
• Reduction of aldehydes and ketones respectively by
powerful reducing agents (e.g. LiAlH4 in dry ether)
produces 1° and 2° alcohols
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33.5 Preparation of Hydroxy Compounds (SB p.217)
Preparation of Phenol
Industrial Process
• Alkaline hydrolysis of chlorobenzene under severe
conditions of high temperature and pressure produces
phenol
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33.5 Preparation of Hydroxy Compounds (SB p.217)
Laboratory Process
• By refluxing benzene and conc. sulphuric(VI) acid
for 1 day to form benzenesulphonic acid and then
subject to alkaline hydrolysis
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33.5 Preparation of Hydroxy Compounds (SB p.217)
•
33
By hydrolysis of benzenediazonium salt
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33.5 Preparation of Hydroxy Compounds (SB p.216)
Example 33-3
Comment on the feasibility of the following preparation of
hydroxy compounds in the school laboratory.
(a)
(b)
KOH
CH3CH2CH2Cl  CH3CH2CH2OH
Solution:
(a) The preparation of the alcohol is feasible in this way.
It is a nucleophilic substitution reaction of
haloalkanes, and the nucleophile is the
Answer
hydroxide ion, OH–.
(b) The preparation of phenol is not feasible in this way.
It is because halobenzenes do not undergo
nucleophilic substitution reactions unless under
severe reaction conditions.
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33.6 Reactions of Alcohols (SB p.218)
Reactions of alcohols can be classified into two main types:
1. Reactions involving the cleavage of the C – O bond:
2. Reactions involving the cleavage of the O – H bond:
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33.6 Reactions of Alcohols (SB p.218)
Reaction Involving Cleavage of the C – O bond
Formation of Haloalkanes
Reaction with Hydrogen Halides
• Alcohols react with hydrogen halides by nucleophilic
substitutions
• The order of reactivity of hydrogen halides:
HI > HBr > HCl
• The order of reactivity of alcohols: 3° > 2° > 1° < methyl
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33.6 Reactions of Alcohols (SB p.219)
Reactions of Alcohols with Hydrogen Chloride
1. Secondary and tertiary alcohols
37
•
2° and 3° alcohols react by SN1 mechanism
•
e.g.
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33.6 Reactions of Alcohols (SB p.219)
Step 1:
Step 2:
38
The alcohol is protonated
The protonated alcohol dissociates to give a
carbocation and water
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33.6 Reactions of Alcohols (SB p.219)
Step 3:
39
The carbocation reacts with a nucleophile to
give the product
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33.6 Reactions of Alcohols (SB p.219)
2. Primary alcohols and methanol
• 1° alcohol and methanol react by SN2 mechanism
Step 1:
40
The alcohol is protonated
New Way Chemistry for Hong Kong A-Level Book 3A
33.6 Reactions of Alcohols (SB p.220)
Step 2: The halide ion displaces a molecule of water from
the carbon to give the product
41
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33.6 Reactions of Alcohols (SB p.220)
Lucas Test
• Lucas reagent: Solution of ZnCl2 in conc. HCl
• Used to to differentiate between simple primary,
secondary and tertiary alcohols
• When an alcohol is treated with Lucas reagent, the
corresponding chloroalkane is formed.
42
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33.6 Reactions of Alcohols (SB p.220)
• 1°, 2°, 3° alcohols react with Lucas reagent at different rates
43
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33.6 Reactions of Alcohols (SB p.221)
• The order of the reactivity of alcohols towards Lucas
reagent:
3° alcohol > 2° alcohol > 1° alcohol
•
44
The reactions are believed to take place via the SN1
mechanism which involves the formation of carbocation
in the rate-determining step
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33.6 Reactions of Alcohols (SB p.221)
The relative stability of carbocations:
 tertiary carbocations are formed rapidly from tertiary
alcohols
 primary carbocations are difficult to form, so
primary alcohols react very slowly
45
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33.6 Reactions of Alcohols (SB p.221)
Reactions of Alcohols with Hydrogen Bromide
• Alcohols react with hydrogen bromide to give
bromoalkanes
• Hydrogen bromide is generated in situ by adding excess
conc. H2SO4 to NaBr
• Iodoalkanes cannot be prepared by reacting HI with
alcohols as iodide will be oxidized by conc. H2SO4
46
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33.6 Reactions of Alcohols (SB p.222)
Reaction with Phosphorus Halides
Laboratory set-up for
the reaction of an
alcohol with PBr3
47
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33.6 Reactions of Alcohols (SB p.222)
• PI3 is used in iodination of alcohols
3R – OH + PI3  3R – I + H3PO3
• Chloroalkanes are formed readily from the reaction of
alcohols with PCl5
R – OH + PCl5  R – Cl + POCl3 + HCl
• SOCl2 converts 1° and 2° alcohols to chloroalkanes
R – OH + SOCl2  R – Cl + SO2 + HCl
(1° or 2°)
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33.6 Reactions of Alcohols (SB p.222)
Dehydration of Alcohols
Formation of Alkenes
• Alkenes are formed when alcohols are heated with
strong acids
• Elimination reactions are favoured at high
temperatures
49
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33.6 Reactions of Alcohols (SB p.223)
Dehydration occurs when passing alcohol vapour over
aluminium oxide at 350°C
Laboratory set-up for dehydration of an alcohol
50
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33.6 Reactions of Alcohols (SB p.223)
• The experimental conditions required to bring the
dehydration are related to the structure of alcohols
• 1° alcohols are the most difficult to dehydrate
e.g.
• 2° alcohols usually dehydrate under milder conditions
e.g.
51
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33.6 Reactions of Alcohols (SB p.223)
• 3° alcohols dehydrate at very mild conditions
e.g.
The order of the relative ease of alcohols to undergo dehydration:
52
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33.6 Reactions of Alcohols (SB p.223)
When 2° or 3° alcohols having more than 3 carbon atoms
is dehydrated, two or more alkenes are formed.
But-2-ene is major product
∵ more highly substituted
alkene (Saytzeff’s rule)
53
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33.6 Reactions of Alcohols (SB p.224)
Formation of Ether
• Dehydration of an alcohol to an ether takes place at
lower temperature than that to an alkene
54
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33.6 Reactions of Alcohols (SB p.225)
Check Point 33-4
Give the structural formula and IUPAC name of the major
product formed by reacting 3-methylpentan-2-ol with
heated aluminium oxide.
Answer
The major product is 3-methylpent-2-ene. Its
structural formula is: CH3CH = C(CH3)CH2CH3
55
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33.6 Reactions of Alcohols (SB p.225)
Reaction Involving Cleavage of the O – H bond
Formation of Alkoxides
• These reactions are less vigorous than the reaction of
the metal with water
∵ alcohols are weaker acids than water
56
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33.6 Reactions of Alcohols (SB p.225)
Example:
• This reaction provides a safe way of disposing sodium
residues
• Addition of water regenerates the alcohol as the
propoxide ion is a very strong base
CH3CH2CH2O–Na+ + H2O  CH3CH2CH2OH + NaOH
• The evolution of hydrogen with sodium metal is a
useful test for the presence of –OH group
57
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33.6 Reactions of Alcohols (SB p.226)
Esterification
Esterification: Alcohols react with carboxylic acids to form
esters through a condensation reaction
e.g.
58
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33.6 Reactions of Alcohols (SB p.226)
•
Esterification reactions are acid-catalyzed
•
Conc. H2SO4 is used as catalyst
• The reactions proceed very slowly in the absence of
catalyst but reach an equilibrium within few hours
when a carboxylic acid and an alcohol are refluxed
with a small amount of conc. H2SO4
• The equilibrium can be shifted to the product side
with the use of an excess of either the carboxylic
acid or the alcohol
• The yield of the reaction can be increased by
removing water from the reaction mixture as it is
formed
59
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33.6 Reactions of Alcohols (SB p.226)
Esters can be synthesized by the reaction of alcohols with
acyl chlorides in the absence of an acid catalyst
e.g.
60
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33.6 Reactions of Alcohols (SB p.227)
Acid anhydrides react with alcohols to form esters in
the absence of an acid catalyst
e.g.
61
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33.6 Reactions of Alcohols (SB p.227)
Oxidation of Alcohols
Oxidation of Primary Alcohols
• 1° alcohols are first oxidized to aldehydes and then to
carboxylic acids by oxidizing agents such as acidified
KMnO4 and acidified K2Cr2O7
62
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33.6 Reactions of Alcohols (SB p.228)
1. Oxidation of primary alcohols to aldehydes
• The oxidation is difficult to stop at the aldehyde
stage because aldehydes are a reducing agent
• To obtain aldehydes, distill off the aldehydes from the
reaction mixture as they are formed
• Oxidizing agent: acidified K2Cr2O7
e.g.
63
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33.6 Reactions of Alcohols (SB p.228)
A laboratory set-up for the conversion of ethanol to ethanal
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33.6 Reactions of Alcohols (SB p.228)
2. Oxidation of primary alcohols to carboxylic acids
• 1° alcohols can be oxidized to carboxylic acids by
powerful oxidizing agents (e.g. acidified KMnO4)
• The oxidation of 1° alcohols by acidified KMnO4 will
not stop at the aldehydes
e.g.
65
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33.6 Reactions of Alcohols (SB p.229)
(a)
(b)
(a) A reflux apparatus for the oxidation of ethanol to ethanoic acid
(b) A distillation apparatus for the separation of ethanoic acid from
the reaction mixture after reflux
66
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33.6 Reactions of Alcohols (SB p.229)
Breathalyser is used by police to
rapidly estimate the ethanol
content of the breath of suspected
drunken drivers
• The breathalyser is based on the oxidation of ethanol
by acidified K2Cr2O7
• As the driver blows into the bag, ethanol
molecules reduce orange Cr2O72- to green Cr3+
67
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33.6 Reactions of Alcohols (SB p.229)
Oxidation of Secondary Alcohols
• 2° alcohols are oxidized to ketones by either acidified
KMnO4 or acidified K2Cr2O7
• 2° alcohols cannot be oxidized to carboxylic acids
because it would involve the breaking of strong
carbon-carbon bond
68
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33.6 Reactions of Alcohols (SB p.230)
Example:
69
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33.6 Reactions of Alcohols (SB p.230)
Oxidation of Tertiary Alcohols
• 3° alcohols are generally resistant to oxidation
∵
oxidation involves the breaking of carboncarbon bonds
• 3° alcohols can be oxidized by acidified KMnO4 to give
a mixture of ketones and carboxylic acids, both with
fewer carbon atoms than the alcohol
e.g.
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New Way Chemistry for Hong Kong A-Level Book 3A
33.6 Reactions of Alcohols (SB p.230)
• 1° alcohols are oxidized to aldehydes which can be
detected by the reaction with 2,4-dinitrophenylhydrazine
or Tollen’s reagent
• 2° alcohols are oxidized to ketones which can be detected
by the reaction with 2,4-dinitrophenylhydrazine but not
Tollen’s reagent
• The carboxylic acid formed from the oxidation of 3°
alcohols can be detected by the reaction with sodium
hydrogencarbonate or ester formation
71
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33.6 Reactions of Alcohols (SB p.230)
Check Point 33-5
Draw the structural formulae for the major organic
products in the following reactions.
(a)
(b)
PCl5
CH3CH2OH 
(a) CH3CH2Cl
P,(b)
Br2
CH3CH2Br
CH3CH2OH 
reflux
(c) CH3CH2CH2Cl
(c)
(d)
(e)
72
SOCl
(d)
CH32CH2COOH
CH3CH2CH2OH 
(e)
K2Cr2O7/H+
Propan-1-ol 
reflux
K2Cr2O7/H+
Propan-2-ol 
reflux
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Answer
33.6 Reactions of Alcohols (SB p.231)
Triiodomethane Formation (Iodoform Reaction)
Alcohols containing the
group react with
iodine in sodium hydroxide (known as iodoform
reagent) to give iodoform (CHI3)
73
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33.6 Reactions of Alcohols (SB p.231)
• The iodoform formed is a yellow crystal with
characteristic odour
• The iodoform test:
The iodoform reaction serves as a test for
alcohols containing the
74
group
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33.6 Reactions of Alcohols (SB p.231)
Example 33-3
Write equations to show how each of the following
transformations can be accomplished. Some conversions
maySolution:
require more than one step.
(a) (a)
(b) (b)
Answer
75
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33.6 Reactions of Alcohols (SB p.231)
Example 33-3
Write
equations to show how each of the following
Solution:
transformations can be accomplished. Some conversions
(c)
may
require more than one step.
(c)
(d)
(d)
Answer
76
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33.6 Reactions of Alcohols (SB p.231)
Example 33-3
Write equations to show how each of the following
transformations can be accomplished. Some conversions
may require more than one step.
Solution:
(e)
(e)
(f)
Answer
(f)
77
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33.6 Reactions of Alcohols (SB p.232)
Example 33-4
Give a simple chemical test that can distinguish between
the compounds in each of the following pairs:
(a)
Ethanol and methoxymethane
Solution:
(b)
andwith
propene
(a)Propan-1-ol
Sodium reacts
ethanol to give hydrogen gas while
methoxymethane
does not.
(c) Propan-1-ol
and propan-2-ol
(b)Pentan-3-ol
Propene decolourizes
bromine in 1,1,1-trichloroethane
Answer
(d)
and pentan-2-ol
while propan-1-ol does not.
(c) On the addition of Lucas reagent, propan-2-ol will give a
cloudy appearance in a shorter time than propan-1-ol.
(d) On the addition of iodine in sodium hydroxide,
pentan-2-ol will give a yellow precipitate (due to the
formation of iodoform) while pentan-3-ol will not.
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New Way Chemistry for Hong Kong A-Level Book 3A
33.6 Reactions of Alcohols (SB p.233)
Check Point 33-6
Draw the structural formulae for the missing products A, B
and C in the reactions below.
Answer
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New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.233)
• The lone pair electrons on oxygen interact with the
delocalized  electron cloud of benzene ring
• The resonance structures withdraw the electron from
oxygen, making it slightly electron-deficient
• This strengthens the C – O bond but weakens the
O – H bond
 reaction of phenols involve the cleavage of O – H
bond
80
New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.234)
Reaction with Sodium
Phenols react with sodium to form sodium phenoxide and
hydrogen gas
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New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.234)
Reaction with Sodium Hydroxide
• Phenol is a weaker acid than carboxylic acids or
mineral acids
 do not react with sodium hydrogencarbonate
• Phenol is a stronger acid than alcohols
 react with sodium hydroxide while alcohols do not
82
New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.234)
Esterification
• Phenol does not react with carboxylic acids to give
esters
∵
the lone pair electrons on oxygen atom
delocalized into the benzene ring, making it less
nucleophilic and less likely to undergo reaction
83
New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.234)
•
Esterification can be carried out by converting phenol
to sodium phenoxide firstly and then treating with
acyl chlorides or acid anhydrides
84
New Way Chemistry for Hong Kong A-Level Book 3A
33.7 Reactions of Phenols (SB p.235)
Examples:
85
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.235)
As Solvents
• Methanol and ethanol are good solvents in the
laboratory and industry
e.g.
methylated spirit (which contains 95%
ethanol/water mixture and 5% methanol) is
commonly used as an industrial solvent
86
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.235)
As Fuels
• Alcohols usually burn with a clean, blue,
hot and non-luminous flame with a
very small amount of soot is formed
• As alcohols are too expensive, they are
not widely use as domestic fuel
Ethanol is used as a
fuel
87
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
As Alcoholic Drinks
• Ethanol is the major component
in alcoholic beverages
• The ethanol is produced by the
fermentation of sugar or starch
88
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
As a Motor Fuel Blending Agent
• Ethanol (80%) is mixed with
gasoline (20%) to produce a
motor fuel, known as gasohol
• Gasohol is an alternative to
gasoline and it produces less
pollutants when burnt
• It is widely used in Brazil where
sugar cane is abundant and
fermented to ethanol
89
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
As an Antifreeze
• Ethane-1,2-diol is formed in the laboratory by bubbling
ethene into a cold and dilute alkaline solution of KMnO4
• Ethane-1,2-diol is miscible with water in all proportions
and has a high boiling point
• Use as an anti-freeze in car radiators in cold countries
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New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
As a Raw Material for Making Terylene
• Terylene (or Dacron) is a polyester which is formed
by condensation polymerization of ethane-1,2-diol
and benzene-1,4-dicarboxylic acid
91
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.237)
• Properties: strong, light and does not ‘wet’
• Uses: making clothing and sails
92
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
As a Raw Material for Making Plastics
Phenol-methanal: by polymerization of phenol and
methanal in acidic medium
Bakelite: using excess methanal, further reactions with
phenol-methanal to form cross links
93
New Way Chemistry for Hong Kong A-Level Book 3A
33.8 Uses of Alcohols (SB p.236)
• Bakelite is a rigid, three-dimensional, cross-linked polymer
• Phenol-methanal and bakelite are thermosetting plastics and
are good insulators of heat and electricity
• Uses: making kitchenware (e.g. handles of saucepans)
and electrical appliances (e.g. electric plugs)
94
New Way Chemistry for Hong Kong A-Level Book 3A
The END
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New Way Chemistry for Hong Kong A-Level Book 3A