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ALCOHOL AND PHENOL
DR. MOHD BAKRI BAKAR
DEPARTMENT OF CHEMISTRYFACULTY OF SCIENCE
UNIVERSITI TEKNOLOGI MALAYSIAC18-208
Source: petroleum & fermentation
As petroleum decreases, demand for alternative fuel.
BIO-FUEL?
Petronas Methanol Labuan
The plant currently produces 660,000 tonnes of methanol per year, using some 55 million standard cubic feet of gas per day as feedstock
Phenolic resin
Structure of AlcoholsStructure of Alcohols
v General formula: R-OH v functional group: hydroxyl (-OH)
Classification of AlcoholsClassification of Alcohols
v Primary ROH:Carbon with –OH is bonded to one other carbon.
v Secondary ROH:Carbon with –OH is bonded to two other carbons.
v Tertiary ROH: Carbon with –OH is bonded to three other carbons.
v Aromatic alcohol or phenol: -OH is bonded to a benzene ring.
IUPAC Nomenclature/NamesIUPAC Nomenclature/Names
v Find the longest carbon chain containing the carbon with the -OH group.
v Drop the -e from the alkane name, add -ol.
v Number the chain, starting from the end closest tothe -OH group.
v Number and name all substituents.
CH3 CH
CH3
CH2OH
CH3 C
CH3
CH3
OH
CH3 CH
OH
CH2CH3
2-methyl-1-propanol
2-methyl-2-propanol
2-butanol
OH
Br CH3
3-bromo-3-methylcyclohexanol
Unsaturated AlcoholsUnsaturated Alcohols
v Priority goes to the hydroxyl group; assign that
carbon the lowest number.
v Use alkene or alkyne name.
4-penten-2-ol
(pent-4-ene-2-ol)
CH2 CHCH2CHCH3
OH
Hydroxy SubstituentHydroxy Substituent
v When -OH is part of a higher priority class of
compound, it is named as hydroxy.
v Example:
CH2CH2CH2COOH
OH
4-hydroxybutanoic acid
Common NamesCommon Names
v Alcohol can be named as alkyl alcohol.
v Useful only for small alkyl groups.
v Examples:
CH3 CH
CH3
CH2OH CH3 CH
OH
CH2CH3
isobutyl alcohol sec-butyl alcohol
Naming Naming DiolsDiols
v Two numbers are needed to locate the two -OH
groups.
v Use -diol as suffix instead of -ol.
HO OH
1,6-hexanediol
GlycolsGlycols
v 1, 2 diols (vicinal diols) are called glycols.
v Common names for glycols use the name of the
alkene from which they were made.
CH2CH2
OH OH
CH2CH2CH3
OH OH
1,2-ethanediol
ethylene glycol1,2-propanediol
propylene glycol
Naming PhenolsNaming Phenols
v -OH group is assumed to be on carbon 1.
v For common names of disubstituted phenols,
use ortho- for 1,2; meta- for 1,3; and para- for
1,4.
v Methyl phenols are cresols.
OH
Cl
3-chlorophenol
meta-chlorophenol
OH
H3C
4-methylphenolpara-cresol
Physical PropertiesPhysical Properties
v Unusually high boiling points due to hydrogen bonding between molecules.
v Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases; why??? “alkyl group is hydrophobic”.
i) B.p. increases as the number of C atoms increases.
Reason: larger surface area of alkyl group, creates more Van der Waals forces, thus requires more energy to boil off.
ii) B.p. decreases as branching increases.
Reason: smaller surface area, smaller van de waals forces.
Boiling PointsBoiling Points
Intermolecular forces involved:a) hydrogen bonding b) dipole-dipole attractions
In increasing order:
Propane < dimethyl ether < ethanol
Solubility in WaterSolubility in Water
Solubility decreases as the size of the alkyl group increases.
Acidity of Alcohols & Acidity of Alcohols & PhenolsPhenols
v Alcohol can function as weak acids (proton donors)
v pKa range: 15.5-18.0 (pKa water = 15.7)
v Not strong enough to react with weak bases (NaHCO3)
v Acidity decreases as alkyl group increases.
- simple alcohol= negatively charged oxygen atoms
accessible for solvation
- bulky group bonded to –OH = ability of water molecules
to solvate the alkoxides ion decreases
CH3O H + O H
H
CH3O + O H
H
H
Formation of Formation of AlkoxideAlkoxide IonsIons
v React methanol and ethanol with sodium metal
v React with base
Formation of Phenoxide IonFormation of Phenoxide Ion
v Phenol reacts with hydroxide ions to form phenoxide
ions
O H
+ OH
O
+ HOH
pKa = 10pKa = 15.7
v Phenoxide ion is more stable; delocalization of the –vecharge via resonance around the benzene ring make it stable; hence increase the acidity
v Phenol is 100 million times more acidic than cyclohexanol
SYNTHESIS OFSYNTHESIS OFALCOHOLSALCOHOLS
Synthesis (Review)Synthesis (Review)
v Nucleophilic substitution on an alkyl halide, RX
v Hydration of alkenes, (-C=C-)
§ water in acid solution (H2O, H+)
§ oxymercuration - demercuration
§ hydroboration - oxidation
v Nucleophilic substitution on an alkyl halide, RX
v Hydration of alkenes
Water in Acid Solution, H2O/H+
v Oxymercuration-Demercuration
– Markovnikov product formed
– Anti addition of H-OH
– No rearrangements
v Hydroboration-Oxidation
– Anti-Markovnikov product formed
– Syn addition of H-OH
OxymercurationOxymercuration -- demercurationdemercuration
v Reagent is mercury(II) acetate which dissociates
slightly to form +Hg(OAc) in H2O.
v +Hg(OAc) is the electrophile, will be attacked by
the pi bond.
v The intermediate is a cyclic mercurinium ion, a three-membered ring with a positive charge.
v Water approaches the mercurinium ion from the side opposite the ring (anti addition).
v Water adds to the more substituted carbon to form the Markovnikov product.
Sodium borohydride (NaBH4), a reducing agent, replaces the mercury with hydrogen.
HydroborationHydroboration -- OxidationOxidation
v Borane, BH3, adds a hydrogen to the most substituted carbon in the double bond.
v The alkylborane is then oxidized to the alcohol which is the anti-Mark product.
HydroborationHydroboration -- OxidationOxidation
HydroborationHydroboration –– Oxidation (continue)Oxidation (continue)
Glycols (Review)Glycols (Review)
v Syn hydroxylation of alkenes
q osmium tetroxide, hydrogen peroxide
q cold, dilute, basic potassium permanganate(BAEYER TEST)- for alkene
Alcohols: Reduction of Carbonyl GroupAlcohols: Reduction of Carbonyl Group
v Reduction of aldehyde yields 1º alcohol.
v Reduction of ketone yields 2º alcohol.
v Reagents:
a) Sodium borohydride, NaBH4
b) Lithium aluminum hydride, LiAlH4
c) Raney nickel
Sodium Borohydride (NaBHSodium Borohydride (NaBH44))
v Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion.
v Then the alkoxide ion is protonated by dilute acid.
v Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids.
HC
O
HC
H
OHC
H
OH HH3O+
Lithium Aluminum Hydride (LiAlHLithium Aluminum Hydride (LiAlH44))
v Stronger reducing agent than sodium borohydride, but dangerousto work with.
v Converts esters and acids to 1º alcohols.
CO
OCH3C
OH H
HH3O+
LAH
Comparison of Reducing Comparison of Reducing AgentsAgents
v LiAlH4 is stronger.
v LiAlH4 reduces more stable compounds which are resistant to reduction.
Catalytic HydrogenationCatalytic Hydrogenation
v Add H2 with Raney nickel catalyst.v Also reduces any C=C bonds.
NaBH4
OH O
H2, Raney Ni
OH
Reaction with CarbonylReaction with Carbonyl
v R:- attacks the partially positive carbon in the
carbonyl.
v The intermediate is an alkoxide ion.
v Addition of water or dilute acid protonates the alkoxide
to produce an alcohol.
Organometallic ReagentsOrganometallic Reagents
v Carbon is bonded to a metal (Mg or Li).
v Carbon is nucleophilic (partially negative).
v It will attack a partially positive carbon:
a) C - X
b) C = O
v A new carbon-carbon bond forms.
Grignard ReagentsGrignard Reagents
v Formula R-Mg-X (reacts like R:- +MgX)
v Stabilized by anhydrous ether
v Iodides most reactive
v May be formed from any halide
a. primary
b. secondary
c. tertiary
d. vinyl
e. aryl
Some Grignard ReagentsSome Grignard Reagents
Br
+ Mgether MgBr
CH3CHCH2CH3
Clether
+ Mg CH3CHCH2CH3
MgCl
CH3C CH2
Br + Mgether
CH3C CH2
MgBr
Organolithium ReagentsOrganolithium Reagents
v Formula R-Li (reacts like R:- +Li)
v Can be produced from alkyl, vinyl, or aryl halides, just like
Grignard reagents.
v Ether not necessary, wide variety of solvents can be used.
Synthesis of 1Synthesis of 1°° AlcoholsAlcohols
v Grignard + formaldehyde yields a primary alcohol with one additional carbon.
C OH
HC
CH3
H3C CH2 C MgBr
H
HH
CH3 CH
CH3
CH2 CH2 C
H
H
O MgBr
HOHCH3 CH
CH3
CH2 CH2 C
H
H
O H
Synthesis of 2º AlcoholsSynthesis of 2º Alcohols
v Grignard + aldehyde yields a secondary alcohol.
MgBrCH3 CH
CH3
CH2 CH2 C
CH3
H
OC
CH3
H3C CH2 C MgBr
H
HH
C OH
H3C
CH3 CH
CH3
CH2 CH2 C
CH3
H
O HHOH
Synthesis of 3º AlcoholsSynthesis of 3º Alcohols
v Grignard + ketone yields a tertiary alcohol.
MgBrCH3 CH
CH3
CH2 CH2 C
CH3
CH3
OC
CH3
H3C CH2 C MgBr
H
HH
C OH3C
H3C
CH3 CH
CH3
CH2 CH2 C
CH3
CH3
O HHOH
PLANNING GRIGNARD SYNTHESIS
CH3CH2C-CH2CH3
C6H5
OH
CH3CH2CCH2CH3
O
C6H5MgBr+
CH3CH2MgBr
C6H5
+ C
CH2CH3
O
2 CH3CH2MgBr
C6H5
+ C
OCH3
O
Grignard ReactionsGrignard Reactionswith Acid Chlorides and Esterswith Acid Chlorides and Esters
v Use two moles of Grignard reagent.
v The product is a tertiary alcohol with
two identical alkyl groups.
v Reaction with one mole of Grignard reagent
produces a ketone intermediate, which reacts
with the second mole of Grignard reagent.
Grignard Reagent + Ethylene OxideGrignard Reagent + Ethylene Oxidev Epoxides are unusually reactive ethers.
v Product is a 1º alcohol with 2 additional carbons.
Grignard Reagent + Ethylene Oxide
MgBr + CH2 CH2
OCH2CH2
O MgBr
HOH
CH2CH2
O H
Reactions of AlcoholsReactions of Alcohols
Types of Alcohol ReactionsTypes of Alcohol Reactions
v Dehydration to alkene
v Oxidation to aldehyde, ketone
v Substitution to form alkyl halide
v Reduction to alkane
v Esterification
vWilliamson synthesis of ether
Dehydration of AlcoholsDehydration of Alcohols
vReversible reaction
vUse concentrated sulfuric (H2SO4) or
phosphoric acid (H3PO4)
vProtonation of OH converts it to a good
leaving group, HOH
vFormed carbocation as intermediate
vProtic solvent removes adjacent H+
MechanismMechanism
Types of AlcoholsTypes of Alcohols
CR
H
OH
H
CR
R'
OH
H
CR
R'
OH
R"
1O 3O2O
Increasing reaction rate of dehydration
SaytzeffSaytzeff RuleRuleIn elimination reactions, the most substituted alkene whichis the most stable alkene, is usually the major product.
Types of Types of CarbocationsCarbocations
CR
H
H
CR
R'
H
CR
R'
R"
1O 3O2O
Increasing stabilityIncreasing stability
CR
R'
R"
3O
CH2 CHCH2
CH2
Rearrangement to form more stable Rearrangement to form more stable carbocationcarbocation
1,2-Hydride Shift
CH3CHCH2OH
CH3 H+
CH3CHCH2
CH3
O H
H
+
CH3C
CH3
CH2
H+
CH3C
CH3
CH2+
H
1,2-Methyl Shift
C
CH3
H3C
CH3
C
H
OH
CH3
H+
C
CH3
H3C
CH3
C
H
O
CH3
H
H+
C
CH3
H3C
CH3
C
H
CH3
-H2O
+C
CH3
H3C C
H
CH3
CH3
+
Ring Expansion
CH2OHH+ CH2 O
H
H+
CH2+
HCH2H
+ +H
Keep in Mind!Keep in Mind!Whenever a reaction leads to the formation
of a carbocation (or radical…), CHECK its
structure for the possibility of
rearrangement.
Oxidation of 2Oxidation of 2°° AlcoholsAlcohols
v 2° alcohol becomes a ketone
v Reagent is; sodium dichromate Na2Cr2O7/H2SO4
v Color change: orange to greenish-blue
CH3CHCH2CH3
OHNa2Cr2O7 / H2SO4
CH3CCH2CH3
O
orange Greenish-blue
Oxidation of 1Oxidation of 1°° AlcoholsAlcohols
v 1° alcohol to aldehyde to carboxylic acid
v Difficult to stop at aldehyde
v Use pyridinium chlorochromate (PCC) to limit the oxidation.
v PCC can also be used to oxidize 2° alcohols to ketones.
CH3CH2CH2CH2
OH N H CrO3Cl
CH3CH2CH2CH
O
33°° Alcohols Don’t OxidizeAlcohols Don’t Oxidize
v Cannot lose 2 H’s
v Basis for chromic acid test
Other Oxidation ReagentsOther Oxidation Reagents
v Collins reagent: CrO3 in pyridine
v Jones reagent: chromic acid in acetone
v KMnO4 (strong oxidizer)
v Nitric acid (strong oxidizer)
v CuO, 300°C (industrial dehydrogenation)
Reduction of AlcoholsReduction of Alcohols
v Dehydrate with conc. H2SO4, then add H2
v Tosylate, then reduce with LiAlH4
CH3CHCH3
OHH2SO4
CH2 CHCH3H2
PtCH3CH2CH3
alcohol alkene alkane
alcohol
CH3CHCH3
OHTsCl
CH3CHCH3
OTsLiAlH4
alkane
CH3CH2CH3
tosylate
p-toluenesulfonyl chlorideTsCl, “tosyl chloride”
CO
H
CH3
S
Cl
OO N
CH3
S OO
OH
C
CH3
S
O
OO
C
ROTs, a tosylate ester
Reaction with HBrReaction with HBr
v -OH of alcohol is protonated
v -OH2+ is good leaving group
v 3° and 2° alcohols react with Br- via SN1
v 1° alcohols react via SN2
H3O+Br-
R O H R O H
H
R Br
1° alcohols react via SN2
3° and 2° alcohols react with Br- via SN1
Reaction with HClReaction with HCl
v Chloride is a weaker nucleophile than bromide.
v Add ZnCl2, which bonds strongly with
-OH, to promote the reaction.
v The chloride product is insoluble.
v Lucas test: ZnCl2 in conc. HCl
v1° alcohols react slowly or not at all.
v2° alcohols react in 1-5 minutes (turbid sol.)
v3° alcohols react in less than 1 minute (turbid
sol.)
Limitations of HX ReactionsLimitations of HX Reactions
v HI does not react
v Poor yields of 1° and 2° chlorides
vMay get alkene instead of alkyl halide
v Carbocation intermediate may rearrange.
Reactions with Reactions with Phosphorus HalidesPhosphorus Halides
v Good yields with 1° and 2° alcohols
v PCl3 for alkyl chloride (but SOCl2 better)
v PBr3 for alkyl bromide
v P and I2 for alkyl iodide (PI3 not stable)
Mechanism with PBrMechanism with PBr33
Reaction with Thionyl ChlorideReaction with Thionyl Chloride
Dehydration ReactionsDehydration Reactions
v Conc. H2SO4 produces alkene
v Carbocation intermediate
v Saytzeff product
v Bimolecular dehydration produces ether
v Low temp, 140°C and below, favors ether
v High temp, 180°C and above, favors alkene
Dehydration MechanismsDehydration Mechanisms
CH3CHCH3
OHH2SO4
alcoholCH3CHCH3
OH
H
CH3CHCH3
CH2 CHCH3H2O
CH3OH
H3O+
CH3OH CH3 OH2 CH3 O
H
CH3
H2OCH3OCH3
=>
Dehydration MechanismsDehydration Mechanisms
Fischer EsterificationFischer Esterification
v Acid + Alcohol yields Ester + Water
v Sulfuric acid is a catalyst.
v Each step is reversible.
CH3COH
Oi)
ii)C6H5CCl
O
CH3COCH2CH3
O
C6H5COCH2CH3
O
Write the product of the reaction of ethanol with
Alkoxide IonsAlkoxide Ions
v ROH + Na (or NaH) yields sodium alkoxide
v RO- + 1° alkyl halide yields ether (Williamson ether synthesis)
Synthesis of phenols1) Alkali fusion of sodium benzenesulfonate (1890)
SO3 , H2SO4SO3H
NaOH
350o C
HCl
ONa+
OH+NaCl
(fusion)sulfonation( )
2) Process cumene (isopropyl benzene)
CH3CH CH2
H2SO4
(kumena)
O2
H3O+
CH3
C
CH3
H
+C
CH3
CH3
OOH OH
CH3
C
CH3
O
CH3CH=CH2 + H2SO4 -à CH3CHCH3
3) Hydrolysis of Chlorobenzene (DOW process)
Cl + NaOH2350oC
150 atmONa
HCl
OH
Reactions of Phenols and Reactions of Phenols and PhenoxidesPhenoxides IonsIons
1. Reduction by catalytic hydrogenation at 300°C
2. Electrophilic Aromatic Substitution (o, p-director)
(with bromin water obtain 2,4,6-tribromophenol)
3. Reaction to the hydroxyl groups
a) formation of phenoxide ions
b) esterification of phenol
phenol + NaOH….+ acyl chloride
phenol + acids/H+,heat
c) formation of ether
phenol + alkyl halide
Reactions of Phenols
Reduction of phenols
Oxidations of phenols –different from alcohol
OH
H2CrO4
O
O
Kuinon
OH
+ 3 H2
Ni
OH
high temperature
Formation of salts
+ NaOH
OH ONa+
+ H2O
(insoluble in water) (its soluble salt)
OH
+ Na very reactive
Esterification reaction of phenols
+
ONa
CH3CO
Cl
O C CH3
O
+ NaCl
Formation of ether
+ CH3CH2
O CH3
+ NaClCl
CH2ONa
Acidity of alcohols and phenols
R OH OH
Both alcohols and phenols contain OH group, and will therefore exhibit a certain degree of acidic properties.
+H2OR OH R O
alkoxide ion pKa =16.0
+H2OOH O
+ H3O+
+ H3O+
pKa = 10.0Phenoxide ion
From pKa values, phenol is more acidic than alcohol. Why?. The answer lies on the degree of stability of the ions formed.
Try doing delocalisation of the negative electron on the alkoxide and phenoxide ions.
O O O O
negative charge on phenoxide ion can be delocalised, thus increasing its stability.
Provide the correct IUPAC names for the following alcohols:
OHOH
OH
CH3(CH2)3CHCH(CH3)2
OH
H2C CHCHCH3
OH
Write the structure for each of the following alcohols:
1) sec-butyl alcohol
2) 3-chloro-2-methylbutanol
3) 4,4-dimethyl-2-cyclohexen-1-ol
Hydration of 3-phenyl-1-butene in dilute H2SO4 is not good method to prepare 3-phenyl-2-butanol, Because 2-phenyl-2-butanol is obtained, why?
H2O, H+
OH
CH3 Hg(OAc)2
NaBH4
BH3.THF
H2O2
OH2, Raney Ni
NaBH4
Show how you would synthesis the following alcohols by adding an appropriate grignard reagent to formaldehyde?
a)OH
b)
OH
c) CH2OH
Show how you would synthesise each alcohol by adding appropriate Grignard reagent to a ketone
a) 1-Methylcyclohexanol
b) Ph3COH
Give the grignard reagent and carbonyl compound that can be used to prepare following alcohols:
CH3CH2CH2OH
OH
CH3CH2C-CH3
Ph
OH
Write the mechanism for reaction of HBr with i) butanol ii) t-butyl alcohol
C
CH3
H3C CH2 OH
CH3HCl
C
CH3
H3C CH2 OH
CH3PBr3
C
CH3
H3C CH2 OH
CH3SOCl2
Determine the products for the following reactions:
Give reagents of following reactions:
OH O
OH
Provide the reagents for following reaction that shows a way to indirectly isomerize alcohols
OH
OH
OH
H2SO4PCC
H2CrO4
PBr3
i) Naii) CH3CH2CH2Br
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