Download - Hydroxy Compounds
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Hydroxy Compounds33.133.1 IntroductionIntroduction
33.233.2 Nomenclature of Hydroxy CompoundsNomenclature of Hydroxy Compounds
33.333.3 Physical Properties of Hydroxy CompoundsPhysical Properties of Hydroxy Compounds
33.433.4 Acidic Properties of Hydroxy CompoundsAcidic Properties of Hydroxy Compounds
33.533.5 Preparation of Hydroxy CompoundsPreparation of Hydroxy Compounds
33.633.6 Reactions of AlcoholsReactions of Alcohols
33.733.7 Reactions of PhenolReactions of Phenol
33.833.8 Uses of AlcoholsUses of Alcohols
Chapter 33Chapter 33
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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
• 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 Secondary alcohol Tertiary alcohol
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33.1 Introduction (SB p.207)
2. Phenols
• Compounds that have a – OH group directly attached t
o a benzene ring
• General formula for phenols: Ar – OH
e.g.
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33.2 Nomenclature of Hydroxy Compounds (SB p.207)
1. Select the longest possible straight chain to which the h
ydroxyl group is directly attached. Change the name of t
he alkane correspending to this chain by dropping the
final ‘-e’ and adding the suffix ‘-ol’.
AlcoholsAlcohols
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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.
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33.2 Nomenclature of Hydroxy Compounds (SB p.207)
Examples:
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33.2 Nomenclature of Hydroxy Compounds (SB p.208)
• 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.
PhenolsPhenols
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Example 33-1Example 33-1For each of the following hydroxy compounds:
(i) Draw the complete structural formula.
(ii) Classify them as primary, secondary or tertiary alcohols.
(a) Hexan-3-ol
(b) 3-Methylbutan-1-ol
(c) 2-MethylcyclopentanolAnswer
33.2 Nomenclature of Hydroxy Compounds (SB p.208)
Solution:
(a) (i)
(ii) A secondary alcohol
(b) (i)
(ii) A primary alcohol
(c) (i)
(ii) A secondary alcohol
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Check Point 33-1 Check Point 33-1
(a) Draw the structural formulae of all isomers of alcohols having the molecular formula C4H10O. Give their
IUPAC names. Answer
33.2 Nomenclature of Hydroxy Compounds (SB p.209)
(a)
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Check Point 33-1 Check Point 33-1
(b) Draw the structural formulae of three isomeric bromophenols with the molecular formula C6H4BrOH. Give their IUPAC names.
Answer
33.2 Nomenclature of Hydroxy Compounds (SB p.209)
(b)
4-Bromophenol
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33.3 Physical Properties of Hydroxy Compounds (SB p.209)
Hydroxy compound
Formula Boiling
point (°C)
Melting point (°C)
Density at 20°C (g cm–
3)
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
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
Phenols:
Phenol
2-Methylphenol
C6H5OH
CH3C6H4OH
182
191
40.9
31.0
1.073
1.046
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33.3 Physical Properties of Hydroxy Compounds (SB p.210)
Boiling Point and Melting PointBoiling 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.
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33.3 Physical Properties of Hydroxy Compounds (SB p.210)
Branching of the carbon chain reduces the surface area in contact with other molecules
Reduction in the extent of intermolecular hydrogen b
onds that can be formed between neighbouring molecules
Isomers of C4H9OH Boiling point (°C)
117
108
99.5
82.5
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33.3 Physical Properties of Hydroxy Compounds (SB p.211)
DensityDensity
• 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)
SolubilitySolubility
• Alcohols with a relatively short carbon chain (e.g. met
hanol, ethanol, propan-1-ol and propan-2-ol) are complet
ely miscible with water
• The solubility decreases as the hydrocarbon chain inc
reases
e.g. the solubility of butan-2-ol is 8 g per 100 g of water
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Check Point 33-2 Check Point 33-2
(a) Arrange the following compounds in order of increasing boiling points:
33.2 Nomenclature of Hydroxy Compounds (SB p.209)
Answer
(a)
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Check Point 33-2 Check Point 33-2
(b) Which member in each of the following pairs is more soluble in water?
(i) CH3CH2OH or CH3CH2CH2CH2OH
(ii)
(iii)
Answer
33.2 Nomenclature of Hydroxy Compounds (SB p.209)
(b) (i) CH3CH2OH
(ii)
(iii)
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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 alko
xide ion formed which is partly influenced by the struct
ure 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
∵ 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
∵ 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 a
nd 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)
The order of acidity of some organic compounds and water:
No reaction
No reaction
CO2 evolved
No reaction
React to give salts and water
React to give salts and water
Alcohols
Phenols
Carboxylic acids
Sodium hydrogencarbonateSodium hydroxide
Simple tests to distinguish alcohols, phenols, carboxylic acids
Phenol is acidic enough to react with NaOH but not Na2CO3
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Example 33-2Example 33-2Arrange the following compounds in order of increasing acidity.
33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
Answer
Solution:
The acidity of the compounds increases in the order:
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Check Point 33-3 Check Point 33-3
Which of the following compounds is more acidic? Explain briefly.
(a) CF3CH2COH and CH3CH2OHAnswer
33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
(a) CF3CH2OH is more acidic, because –CF3 is a strong elec
tron-withdrawing group. It exerts a negative inductive effect on t
he conjugate base of CF3CH2OH (i.e. CF3CH2O–) and thus stabili
zes the CF3CH2O– ion.
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Check Point 33-3 Check Point 33-3
Which of the following compounds is more acidic? Explain briefly.
(b)
Answer
33.4 Acidic Properties of Hydroxy Compounds (SB p.215)
(b) is more acidic. The reason is that the conjugate
base is stabilized by the negative inductive and resonance
effects of the –NO2 group.
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33.5 Preparation of Hydroxy Compounds (SB p.216)
Preparation of AlcoholsPreparation of Alcohols
Fermentation of Carbohydrates
2(C6H10O5)n + nH2O nC12H22O11
C12H22O11 + H2O 2C6H12O6
C6H12O6 2CH3CH2OH + 2CO2
The concentration of ethanol can be increased by
fractional distillation
amylase
60°Cmaltase
15°Czymase
15°C
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33.5 Preparation of Hydroxy Compounds (SB p.216)
Alkaline Hydrolysis of Haloalkanes
• Nucleophilic substitution reaction of haloalkanes w
hereby 1°, 2° and 3° alcohols can be prepared
• The equilibrium lies towards the right
∵ 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 PhenolPreparation 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 f
or 1 day to form benzenesulphonic acid and then subje
ct to alkaline hydrolysis
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• By hydrolysis of benzenediazonium salt
33.5 Preparation of Hydroxy Compounds (SB p.217)
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Example 33-3Example 33-3Comment on the feasibility of the following preparation of hydroxy compounds in the school laboratory.
(a) KOHCH3CH2CH2Cl CH3CH2CH2OH
(b)
Answer
33.5 Preparation of Hydroxy Compounds (SB p.216)
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 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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Reaction Involving Cleavage of the C – O bondReaction Involving Cleavage of the C – O bond
Formation of Haloalkanes
• 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
33.6 Reactions of Alcohols (SB p.218)
Reaction with Hydrogen Halides
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1. Secondary and tertiary alcohols
• 2° and 3° alcohols react by SN1 mechanism
• e.g.
33.6 Reactions of Alcohols (SB p.219)
Reactions of Alcohols with Hydrogen Chloride
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Step 1: The alcohol is protonated
33.6 Reactions of Alcohols (SB p.219)
Step 2: The protonated alcohol dissociates to give a carbocation and water
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Step 3: The carbocation reacts with a nucleophile to give the product
33.6 Reactions of Alcohols (SB p.219)
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2. Primary alcohols and methanol
33.6 Reactions of Alcohols (SB p.219)
• 1° alcohol and methanol react by SN2 mechanism
Step 1: The alcohol is protonated
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Step 2: The halide ion displaces a molecule of water from
the carbon to give the product
33.6 Reactions of Alcohols (SB p.220)
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• 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.
33.6 Reactions of Alcohols (SB p.220)
Lucas Test
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• 1°, 2°, 3° alcohols react with Lucas reagent at different rates
33.6 Reactions of Alcohols (SB p.220)
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• The order of the reactivity of alcohols towards Lucas reagent:
3° alcohol > 2° alcohol > 1° alcohol
33.6 Reactions of Alcohols (SB p.221)
• The reactions are believed to take place via the SN1 mecha
nism which involves the formation of carbocation in the rate-determining step
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The relative stability of carbocations:
33.6 Reactions of Alcohols (SB p.221)
tertiary carbocations are formed rapidly from tertiary alcohols primary carbocations are difficult to form, so primary alcohols react very slowly
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• Alcohols react with hydrogen bromide to give bromoalkanes
• Hydrogen bromide is generated in situ by adding excess conc. H2SO4 to NaBr
33.6 Reactions of Alcohols (SB p.221)
Reactions of Alcohols with Hydrogen Bromide
• Iodoalkanes cannot be prepared by reacting HI with alco
hols as iodide will be oxidized by conc. H2SO4
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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
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• PI3 is used in iodination of alcohols
33.6 Reactions of Alcohols (SB p.222)
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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Dehydration of Alcohols
• Alkenes are formed when alcohols are heated with strong acids
• Elimination reactions are favoured at high temperatures
33.6 Reactions of Alcohols (SB p.222)
Formation of Alkenes
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Dehydration occurs when passing alcohol vapour over alu
minium oxide at 350°C
33.6 Reactions of Alcohols (SB p.223)
Laboratory set-up for dehydration of an alcohol
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• The experimental conditions required to bring the dehydration are related to the structure of alcohols
• 1° alcohols are the most difficult to dehydratee.g.
33.6 Reactions of Alcohols (SB p.223)
• 2° alcohols usually dehydrate under milder conditionse.g.
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33.6 Reactions of Alcohols (SB p.223)
• 3° alcohols dehydrate at very mild conditionse.g.
The order of the relative ease of alcohols to undergo dehydration:
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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)
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• Dehydration of an alcohol to an ether takes place at lower temperature than that to an alkene
33.6 Reactions of Alcohols (SB p.224)
Formation of Ether
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Check Point 33-4 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 structur
al formula is: CH3CH = C(CH3)CH2CH3
33.6 Reactions of Alcohols (SB p.225)
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33.6 Reactions of Alcohols (SB p.225)
• These reactions are less vigorous than the reaction of the metal with water ∵ alcohols are weaker acids than water
Reaction Involving Cleavage of the O – H bondReaction Involving Cleavage of the O – H bond
Formation of Alkoxides
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Example:
33.6 Reactions of Alcohols (SB p.225)
• This reaction provides a safe way of disposing sodium residues
• Addition of water regenerates the alcohol as the propoxide ion is a very strong baseCH3CH2CH2O–Na+ + H2O CH3CH2CH2OH + NaOH
• The evolution of hydrogen with sodium metal is a useful test for the presence of –OH group
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33.6 Reactions of Alcohols (SB p.226)
Esterification: Alcohols react with carboxylic acids to form esters through a condensation reaction
Esterification
e.g.
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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
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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.
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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.
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33.6 Reactions of Alcohols (SB p.227)
• 1° alcohols are first oxidized to aldehydes and then to
carboxylic acids by oxidizing agents such as acidified
KMnO4 and acidified K2Cr2O7
Oxidation of Alcohols
Oxidation of Primary Alcohols
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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.
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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.
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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
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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 Cr2O7
2- to green Cr3+
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33.6 Reactions of Alcohols (SB p.229)
• 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
Oxidation of Secondary Alcohols
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33.6 Reactions of Alcohols (SB p.230)
Example:
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33.6 Reactions of Alcohols (SB p.230)
• 3° alcohols are generally resistant to oxidation ∵ oxidation involves the breaking of carbon-
carbon bonds
• 3° alcohols can be oxidized by acidified KMnO4 to giv
e a mixture of ketones and carboxylic acids, both with fewer carbon atoms than the alcohol
Oxidation of Tertiary Alcohols
e.g.
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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
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Check Point 33-5 Check Point 33-5
Draw the structural formulae for the major organic products in the following reactions.
(a) PCl5CH3CH2OH
(b) P, Br2CH3CH2OH
reflux
(c) SOCl2CH3CH2CH2OH
(d) K2Cr2O7/H+
Propan-1-ol reflux
(e) K2Cr2O7/H+
Propan-2-ol reflux
Answer
33.6 Reactions of Alcohols (SB p.230)
(a) CH3CH2Cl
(b) CH3CH2Br
(c) CH3CH2CH2Cl
(d) CH3CH2COOH
(e)
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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)
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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 group
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Example 33-3Example 33-3Write equations to show how each of the following transformations can be accomplished. Some conversions may require more than one step.
(a)
(b)
33.6 Reactions of Alcohols (SB p.231)
Answer
Solution:
(a)
(b)
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Example 33-3Example 33-3Write equations to show how each of the following transformations can be accomplished. Some conversions may require more than one step.
(c)
(d)
33.6 Reactions of Alcohols (SB p.231)
Answer
Solution:
(c)
(d)
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Example 33-3Example 33-3Write equations to show how each of the following transformations can be accomplished. Some conversions may require more than one step.
(e)
(f)
33.6 Reactions of Alcohols (SB p.231)
Answer
Solution:
(e)
(f)
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Example 33-4Example 33-4Give a simple chemical test that can distinguish between the compounds in each of the following pairs:
(a) Ethanol and methoxymethane
(b) Propan-1-ol and propene
(c) Propan-1-ol and propan-2-ol
(d) Pentan-3-ol and pentan-2-ol Answer
Solution:
(a) Sodium reacts with ethanol to give hydrogen gas while methoxymethane does not.
(b) Propene decolourizes bromine in 1,1,1-trichloroethane 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 fo
rmation of iodoform) while pentan-3-ol will not.
33.6 Reactions of Alcohols (SB p.232)
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Check Point 33-6 Check Point 33-6
Draw the structural formulae for the missing products A, B and C in the reactions below.
33.6 Reactions of Alcohols (SB p.233)
Answer
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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
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Reaction with Sodium
Phenols react with sodium to form sodium phenoxide and
hydrogen gas
33.7 Reactions of Phenols (SB p.234)
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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
33.7 Reactions of Phenols (SB p.234)
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Esterification
• Phenol does not react with carboxylic acids to give e
sters
∵ the lone pair electrons on oxygen atom deloc
alized into the benzene ring, making it less nucle
ophilic and less likely to undergo reaction
33.7 Reactions of Phenols (SB p.234)
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• Esterification can be carried out by converting phenol
to sodium phenoxide firstly and then treating with ac
yl chlorides or acid anhydrides
33.7 Reactions of Phenols (SB p.234)
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Examples:
33.7 Reactions of Phenols (SB p.235)
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• Methanol and ethanol are good solvents in the labora
tory and industry
e.g. methylated spirit (which contains 95% etha
nol/water mixture and 5% methanol) is commonly
used as an industrial solvent
33.8 Uses of Alcohols (SB p.235)
As SolventsAs Solvents
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• 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
33.8 Uses of Alcohols (SB p.235)
As FuelsAs Fuels
Ethanol is used as a fuel
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• Ethanol is the major component
in alcoholic beverages
• The ethanol is produced by the
fermentation of sugar or starch
33.8 Uses of Alcohols (SB p.236)
As Alcoholic DrinksAs Alcoholic Drinks
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• 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
33.8 Uses of Alcohols (SB p.236)
As a Motor Fuel Blending AgentAs a Motor Fuel Blending Agent
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• Ethane-1,2-diol is formed in the laboratory by bubbling ethene into a cold and dilute alkaline solution of KMnO4
33.8 Uses of Alcohols (SB p.236)
As an AntifreezeAs an Antifreeze
• 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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• Terylene (or Dacron) is a polyester which is formed by condensation polymerization of ethane-1,2-diol and benzene-1,4-dicarboxylic acid
33.8 Uses of Alcohols (SB p.236)
As a Raw Material for Making TeryleneAs a Raw Material for Making Terylene
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• Properties: strong, light and does not ‘wet’
• Uses: making clothing and sails
33.8 Uses of Alcohols (SB p.237)
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Phenol-methanal: by polymerization of phenol and methanal in acidic medium
Bakelite: using excess methanal, further reactions with phenol-methanal to form cross links
33.8 Uses of Alcohols (SB p.236)
As a Raw Material for Making PlasticsAs a Raw Material for Making Plastics
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• 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)
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The END