ALCOHOL AND PHENOL

DR. MOHD BAKRI BAKAR

DEPARTMENT OF CHEMISTRYFACULTY OF SCIENCE

UNIVERSITI TEKNOLOGI MALAYSIAC18-208

bakri@kimia.fs.utm.my

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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