1 dr nahed elsayed. learning objectives chapter six concerns alcohols and phenols and by the end of...

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Dr Nahed Elsayed

Learning ObjectivesLearning ObjectivesChapter six concerns alcohols and phenols and by the end of this chapter the student Chapter six concerns alcohols and phenols and by the end of this chapter the student will:will: know the difference in structure between alcohols and phenolsknow the difference in structure between alcohols and phenolsKnow the different classes of alcoholsKnow the different classes of alcohols Know how to name alcohols and phenolsKnow how to name alcohols and phenols Know the physical properties (solubility, boiling and melting points) Know the physical properties (solubility, boiling and melting points) Know how hydrogen bonds are formed and its effect on boiling points of Know how hydrogen bonds are formed and its effect on boiling points of alcoholsalcoholsKnow the acidic properties of alcohols and phenolsKnow the acidic properties of alcohols and phenolsknow the different methods that can be used to prepare alcohols and know the different methods that can be used to prepare alcohols and phenols.phenols. Know the chemical reactions of these compounds ( some reactions are Know the chemical reactions of these compounds ( some reactions are review, others are extensions of the chemistry that will be discussed on review, others are extensions of the chemistry that will be discussed on chapters 8, 9 & 10 chapters 8, 9 & 10

145 Chem.

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King Saud University Chemistry Department

Alcohols and phenols may be viewed as organic derivatives of water.

Alcohols and phenols have a common functional group, the hydroxyl group, —OH.

- In alcohols the hydroxyl group is attached to an alkyl group, —R.

- In phenols the hydroxyl function is directly attached to benzene

ring

H-O-H R-O-H or PhCH2OH Ph-O-H Water Alcohol Phenol

Structure Of Alcohols and PhenolsStructure Of Alcohols and Phenols

OHOH

Phenol Benzyl alcohol

OH

Cyclohexanol

Alcohols are classified according to the type of the according to the type of the carbon atom connected to the hydroxyl group (carbinol carbon atom connected to the hydroxyl group (carbinol carbon) carbon) into:

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Classification and Nomenclature of Alcohols

145 Chem.

1.1. Select the Select the longest continuous longest continuous carbon chain that carbon chain that contains the -OH groupcontains the -OH group. Replace . Replace the the ending ending ee of the alkane by the suffix of the alkane by the suffix –ol–ol

22. . If a molecule contains both an -OH group and a C=C or cIf a molecule contains both an -OH group and a C=C or cΞΞc bond; c bond; Choose the chain that include both of them even if this is not the longest chain. Choose the chain that include both of them even if this is not the longest chain.

The name should include suffixes indicate presence of both the OH group and the The name should include suffixes indicate presence of both the OH group and the unsaturated groups. unsaturated groups.

The The OH group takes precedence over the double or triple bonds in getting the OH group takes precedence over the double or triple bonds in getting the lower number.lower number.

Cyclic alcohols Cyclic alcohols are named using the prefixare named using the prefix cyclo-, cyclo-, the carbon bearing the hydroxyl the carbon bearing the hydroxyl group is assumed to take group is assumed to take number 1.number 1.

3. 3. The suffix The suffix dioldiol or or trioltriol is added to the name of the parent hydrocarbon when there are is added to the name of the parent hydrocarbon when there are two OH or three OH groups respectively.two OH or three OH groups respectively.

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NOMENCLATURE OF ALCOHOLSNOMENCLATURE OF ALCOHOLSIUPAC Nomenclature Of Alcohols IUPAC Nomenclature Of Alcohols

Alcohols are named according to the following rules:

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Common Nomenclature Of AlcoholsCommon Nomenclature Of Alcohols

List the names of alkyl substituents attached to the hydroxyl group, followed by the word alcohol.

If two OH groups present on two adjacent carbons these known as glycols


Primary alcoholsPrimary alcohols

CH3OH CH3CH2OH CH2=CHCH2OH

Common

Methyl alcohol Ethyl alcohol Allyl alcohol

IUPAC Methanol Ethanol 2-Propen-1-ol

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Secondary and tertiary alcoholsSecondary and tertiary alcohols

Common

Isopropyl alcohol

Cyclopentyl alcohol

Methylcyclohexyl alcohol

IUPAC 2-Propanol Cyclopentanol1-Methyl-1-cyclohexanol

CH3

OH

OHOH


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OH

OHOH

OH

OH4-Methyl-2-cyclohexen-1-ol

1-PhenylmethanolBenzyl alcohol (common

name)

2-Phenylethanol

Ethan-1,2-diolEthylene glycol (common name)


ExamplesExamples

(CH3)2C=CHCH(OH)CH3

12345

4- Methyl-3-penten-2-ol

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ExamplesExamples

CH3

OH

OH

Propylene glycol

OHHO

Ethylene glycol

Ethane-1,2-diol Propane-1,2-diolor 1,2-Propanediol

OH

OH

OH

Propane-1,2,3-triolor 1,2,3,-Propantriol

IUPAC

Common Glycerol or Glycerin


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OH OH

But-3-en-2-ol

OH

Pent-4-yn-1-ol 5-Ethyl-hex-5-en-3-olOH

Cl

4-Chloro-2-methyl-1-penten-3-ol

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Alcohol and water contain Alcohol and water contain hydroxyl group hydroxyl group that can form that can form hydrogen bonds.hydrogen bonds.The hydroxyl group isThe hydroxyl group is hydrophilic “water loving” hydrophilic “water loving”The alkyl group of alcohols isThe alkyl group of alcohols is hydrophobic “ water hating” hydrophobic “ water hating”As the number of the –OH group in alcoholAs the number of the –OH group in alcohol increases, the solubility increases, the solubility in water in water increases.increases.The lower The lower alcohols are alcohols are completely miscible completely miscible with waterwith water

Diols and triols are Diols and triols are moremore soluble in water than monohydroxyalcohols. soluble in water than monohydroxyalcohols.

As the number of carbons in the alcohol increases, As the number of carbons in the alcohol increases, the solubility in water decreases.the solubility in water decreases.


Physical Properties of AlcoholsPhysical Properties of Alcohols1) Solubility Of Alcohols and 1) Solubility Of Alcohols and

PhenolsPhenols

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Physical Properties of AlcoholsPhysical Properties of Alcohols2) Boiling Points of Alcohols2) Boiling Points of Alcohols

The boiling points increase with increase in molecular weights.The boiling points increase with increase in molecular weights.

Alcohols have higher boiling points(b .p.) than alkanes of similar weight Alcohols have higher boiling points(b .p.) than alkanes of similar weight this is due to the presence of this is due to the presence of hydrogen bondshydrogen bonds between molecules of between molecules of alcohols.alcohols.

hydrogen bond

OH

OH

OH> >

OHOH

OH> > > Br >Melting & boiling points

Increases in this direction

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3)3)Acidic Properties of AlcoholsAcidic Properties of Alcohols Alcohols are Alcohols are very weak acidsvery weak acidsThe hydroxyl proton of an alcohol is weakly acidicThe hydroxyl proton of an alcohol is weakly acidicA strong base can abstract the hydroxyl proton to give an alkoxide ionA strong base can abstract the hydroxyl proton to give an alkoxide ion

Electron-withdrawing group (-I) Electron-withdrawing group (-I) increase acidityincrease acidityElectron-releasing group (+I)Electron-releasing group (+I) decrease acidity decrease acidity

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R-O-H B+ B-H

CH3CH2OH CH3OH ClCH2CH2OH

PKa= 15.9 15.5 15.3less acidic most acidic

R-O

Cl

Cl

Cl

OH

Cl

OH OH

H3CO

OH> >>

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H3O+ OH+

OHmajor minor

KMnO4

OH-/H2O

OH

OHcis glycol

alcohol,KOH

CH3CH2CH2Cl

heat

dil OH-

CH3CH2CH2OH

H3C CH

CH2


Synthesis (Preparation) of Synthesis (Preparation) of AlcoholsAlcohols1- From Alkenes (Hydration and oxidation of alkenes)1- From Alkenes (Hydration and oxidation of alkenes)

2- From alkyl halide by nucleophilic substitution2- From alkyl halide by nucleophilic substitution (N.B. elimination of HX using base gives alkene(N.B. elimination of HX using base gives alkene

i) i) Hydration of alkenesHydration of alkenes

ii) ii) Oxidation of alkenesOxidation of alkenes

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LiAlH4CH3CCH3 or NaBH4

or H2/Pt

H3CHC CH3

O

OH

CH3 MgBrCH3CH H3C

HC CH3

O

OMgBr

H3O+

H3CHC CH3

OH

LiAlH4CH3COH H3C

H2C OH

O


3- Reduction of aldehydes, ketones and carboxylic 3- Reduction of aldehydes, ketones and carboxylic acidsacids

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CH3CCH3

O

OMgBr

H3O++

MgCl C CH3H3C

OH

C CH3H3C


4- Addition of Grignard compounds to aldehydes 4- Addition of Grignard compounds to aldehydes & ketones& ketones

Tertiary alcohol

Ketone

CH3 MgBrCH3CH H3C

HC CH3

O

OMgBr

H3O+

H3CHC CH3

OH

CH3 MgBrH

HC CH3

OMgBr

H3O+

HHC CH3

OHH H

O

Secondary alcohol

Primary alcohol

Methanalformaldehyde

A. Formation of Salt

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1. Dissociation of O-H Bond

NaCH3CH2OH H3C

H2C ONa

Sodium ethoxide


Reaction of AlcoholsReaction of Alcohols

B. Formation of Esters

R OH

O

+ R- OHR OR

OH+

H+/ H2O

A. Elimination Reactions

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conc.H2SO4CH3CH2OH H2C CH2


B. Substitution Reaction

2. Dissociation of C-O Bond i.e. cleavage of CــــOH bond

HCl/ ZnCl2CH3CH2OH H3C CH2Clor SOCl2or PCl3or PCl5

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C. Oxidation Reactions

CH3CH2OH H3C C-OH

OKMnO4

PCC =N

, CrO3. HCl Pridinium Chloro chromate

Cu /CH3CH2OH H3C CH

or PCC

O

Cu /CH3CHCH3 H3C C-CH3

or KMnO4

OOH

or PCC

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Phenols (compounds having hydroxyl group directly attached to a benzene ring ) are generally named as derivatives of the simplest member of the family, phenol

Acidity :

Alcohols and phenols have weak acidic properties.

Phenols are much stronger acids than alcohols.

Introduction of electron-withdrawing groups, such as NO2 or

CN, on the ring increases the acidity of phenols.

Nomenclature and acidity of Phenols


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OH OH OH OH OH

CH3 NO2

NO2

NO2NO2

NO2O2N

< < < <

2,4,6-TrinitrophenolPicric acid

Cresol Phenol p-Nitrophenol 2,4,-DinitrophenolpH > 10 pH= 10 pH= 7 pH=4

pH= 0.25


OH

CHO

OH

COOH

OH

Cl NH22-Hydroxy-benzaldehydeo-Hydroxybenzaldehyde

Salicylaldehyde2-Hydroxy-benzoic acido-Hydroxybenzoic acid

Salicylic acid

3-Amino-5-chloro-phenol

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Synthesis of PhenolsSynthesis of Phenols


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Reactions PhenolsReactions Phenols


Ethers formationEthers formation

CrO3 / H+

O

O

p-Benzoquinone

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2. Electrophilic Substitution Reactions

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Home Work

KMnO4

OH-/H2O

HCH

OH3O+

+

MgCl

MgBr

H3O+

+

O H2C


4) The IUPAC name of is:

A) 4-Ethyl-5-heptyn-3-ol B) 4-Ethyl-5-heptan-3-olC) 4-Ethyl-5-hepten-3-olD) 4-Etyl-2-hepten-5-ol

OH

5) The IUPAC name of is:

A) 3-Methyl-1-bromocyclohexanolB) 2-Bromo-3-methylcyclohexanolC) 4-Bromo-2-methylcyclohexanolD) 3-Bromo-1-methylcyclohxanol

HO

H3C Br

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OH OH

OCH3 NO2

OH

A) B) C) D)CH3CH2OH

6) The most acidic compound is

7) The common name of 2-methyl-2-propanol is:A) Allyl alcoholB) Isopropyl alcoholC) tert-Butyl alcoholD) Benzyl alcohol

8) The following reaction gives

A) 4-EthylphenolB) 2-EthylphenolC) Ethylphenyl etherD) Ethylphenyl ketone

NaOHOH

1)

CH3-CH2-Br2)

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27

CH3

OH

Conc. H2SO4

a) b) c) d)

KMnO4/OH-

OH

HOH

OH

OH

H

H

H

OH

OH

H

H

OH

H

a) b) c) d)

10) The product of the reaction shown below is

O

H

O OH OCH3A) B) C) D)

11) Which of the following compounds has the highest boiling point?

9) The major product for the following reaction is

Questions?

1 dr nahed elsayed. learning objectives chapter six concerns alcohols and phenols and by the end of...

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