Alcohols , enols and phenols

AlcoholsAlcohols, enols and , enols and phenolsphenols

Alcohols and alkyl halides are classified asAlcohols and alkyl halides are classified asprimaryprimarysecondarysecondarytertiarytertiary

according to their "degree of substitution."according to their "degree of substitution."

Degree of substitution is determined by countingDegree of substitution is determined by countingthe number of carbon atoms directly attached tothe number of carbon atoms directly attached tothe carbon that bears the halogen or hydroxyl group.the carbon that bears the halogen or hydroxyl group.

ClassificationClassification

CHCH33CHCH22CHCH22CHCH22CHCH22FF

CHCH33CHCHCHCH22CHCH22CHCH33

BrBr

primary alkyl halideprimary alkyl halide

secondary alkyl halidesecondary alkyl halide

ClassificationClassification

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

tertiary alcoholtertiary alcohol

HH

OHOH

secondary alcoholsecondary alcohol

IUPAC NomenclatureIUPAC Nomenclature

of Alcoholsof Alcohols

Name the alkyl group and add "alcohol" as aName the alkyl group and add "alcohol" as aseparate word.separate word.

Functional Class Nomenclature of AlcoholsFunctional Class Nomenclature of Alcohols

CHCH33CHCH22OHOH

CHCH33CHCHCHCH22CHCH22CHCH22CHCH33

OHOH

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

Name the alkyl group and add "alcohol" as aName the alkyl group and add "alcohol" as aseparate word.separate word.

Functional Class Nomenclature of AlcoholsFunctional Class Nomenclature of Alcohols

CHCH33CHCH22OHOH

CHCH33CHCHCHCH22CHCH22CHCH22CHCH33

OHOH

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

Ethyl alcoholEthyl alcohol

1-Methylpentyl alcohol1-Methylpentyl alcohol

1,1-Dimethylbutyl1,1-Dimethylbutylalcoholalcohol

Name as "alkanols." Replace -e ending of alkaneName as "alkanols." Replace -e ending of alkanename by -ol.name by -ol.

Number chain in direction that gives lowest numberNumber chain in direction that gives lowest numberto the carbon that bears the —OH group.to the carbon that bears the —OH group.

Substitutive Nomenclature of AlcoholsSubstitutive Nomenclature of Alcohols

CHCH33CHCH22OHOH

CHCH33CHCHCHCH22CHCH22CHCH22CHCH33

OHOH

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

Name as "alkanols." Replace -e ending of alkaneName as "alkanols." Replace -e ending of alkanename by -ol.name by -ol.

Number chain in direction that gives lowest numberNumber chain in direction that gives lowest numberto the carbon that bears the —OH group.to the carbon that bears the —OH group.

Substitutive Nomenclature of AlcoholsSubstitutive Nomenclature of Alcohols

CHCH33CHCH22OHOH

CHCH33CHCHCHCH22CHCH22CHCH22CHCH33

OHOH

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

EthanolEthanol

2-Hexanol2-Hexanol2-Methyl-2-pentanol2-Methyl-2-pentanol

OHOH

CHCH33

Substitutive Nomenclature of AlcoholsSubstitutive Nomenclature of Alcohols

Hydroxyl groups outrank Hydroxyl groups outrank alkyl groups when alkyl groups when it comes to numberingit comes to numberingthe chain.the chain.

Number the chain in theNumber the chain in thedirection that gives the direction that gives the lowest number to thelowest number to thecarbon that bears thecarbon that bears theOH groupOH group

CHCH33

OHOH

Substitutive Nomenclature of AlcoholsSubstitutive Nomenclature of Alcohols

6-Methyl-3-heptanol6-Methyl-3-heptanol

5-Methyl-2-heptanol5-Methyl-2-heptanol

OHOH

CHCH33

CHCH33

OHOH

alcohols and alkyl halides are polaralcohols and alkyl halides are polar

= 1.7 D= 1.7 D = 1.9 D= 1.9 D

Dipole MomentsDipole Moments

4646

+78+78

1.71.7

CHCH33CHCH22OHOH

MolecularMolecularweightweight

BoilingBoilingpoint, °Cpoint, °C

DipoleDipolemoment, Dmoment, D

Highest boiling point;Highest boiling point;strongest intermolecularstrongest intermolecularattractive forces.attractive forces.

Hydrogen bonding isHydrogen bonding isstronger than otherstronger than otherdipole-dipole attractions.dipole-dipole attractions.

Effect of Structure on Boiling PointEffect of Structure on Boiling Point

Hydrogen bonding in ethanolHydrogen bonding in ethanol

high yieldshigh yields

not reversible when carried outnot reversible when carried outin presence of pyridinein presence of pyridine

Reaction of Alcohols with Acyl ChloridesReaction of Alcohols with Acyl Chlorides

ROROHH HClHCl++ ++R'CClR'CCl

OO

R'CR'COROR

OO

a condensation reactiona condensation reaction

called Fischer esterificationcalled Fischer esterification

acid catalyzedacid catalyzed

reversiblereversible

EsterificationEsterification

ROROHH HH22OO++

HH++

++R'COHR'COH

OO

R'CR'COROR

OO

analogous to reaction with acyl chloridesanalogous to reaction with acyl chlorides

Reaction of Alcohols with Acid AnhydridesReaction of Alcohols with Acid Anhydrides

ROROHH ++ ++R'CR'COROR

OOOO

R'COCR'R'COCR'

OO

R'COHR'COH

OO

Esters of Inorganic AcidsEsters of Inorganic Acids

ROROH + HOH + HOEWGEWG ROROEWGEWG + H + H22OO

EWGEWG is an electron-withdrawing group is an electron-withdrawing group

HONOHONO22 (HO)(HO)22SOSO22 (HO)(HO)33PP OO++ ––

Primary alcoholsPrimary alcohols

Secondary alcoholsSecondary alcohols

from Hfrom H22OO

Oxidation of AlcoholsOxidation of Alcohols

RCHRCH22OHOH

OO

RCHRCH

OO

RCOHRCOH

OO

RCR'RCR'RCHR'RCHR'

OHOH

alcohol alcohol dehydrogenasedehydrogenase

Enzyme-catalyzedEnzyme-catalyzed

CHCH33CCHH22OHOH ++ NAD (a coenzyme)NAD (a coenzyme)++

++ ++ ++HHNADNAD HHCHCH33CCHH OO

Cleavage of Vicinal Diols by Periodic AcidCleavage of Vicinal Diols by Periodic Acid

CCCC

HOHO OHOH

HIOHIO44CC OO OO CC++

Enols and EnolatesEnols and Enolates

Enol-oxo tautomerismEnol-oxo tautomerism

CHCH33CHCH

OO

HH22CC CHCH

OHOH

KK = 3 x 10 = 3 x 10-7-7

CHCH33CCHCCH33

OO

HH22CC CCHCCH33

OHOH

KK = 6 x 10 = 6 x 10-9-9

Mechanism of EnolizationMechanism of Enolization (In general)(In general)

OO••••

CR'CR'

••••

RR22CC

HH

RR22CC CR'CR'

OO••••

•••• HH

percent enol is usually very smallpercent enol is usually very small

keto form usually 45-60 kJ/mol more stableketo form usually 45-60 kJ/mol more stablethan enolthan enol

Enol ContentEnol Content

RR22CHCR'CHCR'

OO

RR22CC CR'CR'

OHOH

enolenolketoketo

PhenolsPhenols

named on basis of phenol as parentnamed on basis of phenol as parent

substituents listed in alphabetical ordersubstituents listed in alphabetical order

lowest numerical sequence: first point oflowest numerical sequence: first point ofdifference ruledifference rule

5-5-ChloroChloro-2--2-methylmethylphenolphenol

NomenclatureNomenclature OHOH

CHCH33

ClCl

NomenclatureNomenclature OHOH

OHOH

1,2-Benzenediol1,2-Benzenediol

OHOH

OHOH

OHOH

OHOH

1,3-Benzenediol1,3-Benzenediol 1,4-Benzenediol1,4-Benzenediol

(common name:(common name:pyrocatechol)pyrocatechol)

(common name:(common name:resorcinol)resorcinol)

(common name:(common name:hydroquinone)hydroquinone)

name on basis of benzoic acid as parentname on basis of benzoic acid as parent

higher oxidation states of carbon outrankhigher oxidation states of carbon outrankhydroxylhydroxyl group group

NomenclatureNomenclature

pp-Hydroxybenzoic acid-Hydroxybenzoic acid

OHOH

COCO22HH

phenol is planarphenol is planar

C—O bond distance is 136 pm, which isC—O bond distance is 136 pm, which isslightly shorter than that of CHslightly shorter than that of CH33OH (142 pm)OH (142 pm)

Structure of PhenolStructure of Phenol

The OH group of phenols allows hydrogen bondingThe OH group of phenols allows hydrogen bonding

to other phenol molecules and to water.to other phenol molecules and to water.

Physical PropertiesPhysical Properties

HH OOOO

Hydrogen Bonding in PhenolsHydrogen Bonding in Phenols

Acidity of PhenolsAcidity of Phenols

most characteristic property of most characteristic property of

phenols is their acidityphenols is their acidity

CompareCompare OO HH••••••••

KKaa = 10 = 10-10-10

++HH ++

OO•••••••• ••••

––

CHCH33CHCH22OO HH••••

••••

KKaa = 10 = 10-16-16

++HH ++ CHCH33CHCH22OO••••

••••

––••••

Effect of strong electron-withdrawing groupsEffect of strong electron-withdrawing groupsis cumulativeis cumulative OHOH

NONO22

OHOH

NONO22

NONO22

OHOH

NONO22

NONO22

OO22NN

KKaa:: 7 x 107 x 10-8-8 1 x 101 x 10-4-4 4 x 104 x 10-1-1

CH(CHCH(CH33))22

OHOH

CHCH33

ThymolThymol

(major constituent of oil of thyme)(major constituent of oil of thyme)

Example: ThymolExample: Thymol

ClCl

OHOH

ClCl

2,5-Dichlorophenol2,5-Dichlorophenol

(from defensive secretion of(from defensive secretion of

a species of grasshopper)a species of grasshopper)

Example: 2,5-DichlorophenolExample: 2,5-Dichlorophenol

O-AcylationO-Acylation

(95%)(95%)

in the absence of AlClin the absence of AlCl33, acylation of the , acylation of the

hydroxyl group occurs (O-acylation)hydroxyl group occurs (O-acylation)

OOHH

CHCH33(CH(CH22))66CClCCl

OO

++

OOC(CHC(CH22))66CHCH33 OO

Typical Preparation is by Williamson SynthesisTypical Preparation is by Williamson Synthesis OONaNa ++ RRXX

OORR NaNaXX++

SSNN22

ExampleExample

acetoneacetone

heatheat

OONaNa ++ CHCH33II

OOCHCH33

(95%)(95%)

The most common examples of phenol oxidationsThe most common examples of phenol oxidationsare the oxidations of 1,2- and 1,4-benzenediolsare the oxidations of 1,2- and 1,4-benzenediolsto give quinones. to give quinones.

(76-81%)(76-81%)

QuinonesQuinones OHOH

OHOH

OO

OO

NaNa22CrCr22OO7,7, H H22SOSO44

HH22OO

The most common examples of phenol oxidationsThe most common examples of phenol oxidationsare the oxidations of 1,2- and 1,4-benzenediolsare the oxidations of 1,2- and 1,4-benzenediolsto give quinones. to give quinones.

(68%)(68%)

QuinonesQuinones

OO

OOAgAg22OO

diethyl etherdiethyl ether

OHOH

OHOH

CHCH33

CHCH33

AlizarinAlizarin(red pigment)(red pigment)

Some quinones are dyesSome quinones are dyes OO

OO

OHOH

OHOH

Ubiquinone (Coenzyme Q)Ubiquinone (Coenzyme Q)nn = 6-10 = 6-10

involved in biological electron transportinvolved in biological electron transport

Some quinones are important biomoleculesSome quinones are important biomolecules

CHCH33OO

CHCH33OO

OO

OO

CHCH33

nn

Vitamin KVitamin K(blood-clotting factor)(blood-clotting factor)

Some quinones are important biomoleculesSome quinones are important biomolecules OO

CHCH33

OO CHCH33 CHCH33 CHCH33 CHCH33

CHCH33