Lecture 16 - Alcohols, Phenols

General

Organic ChemistryTwo credits

Second Semester 2009

King Saud bin Abdulaziz University for Health Science

Reference Book: Organic Chemistry: A Brief Course, by Robert C. Atkins and Francis A. CareyThird Edition

Instructor: Rabih O. Al-Kaysi, PhD.

Chapter 10Chapter 10

Alcohols, Ethers and PhenolsAlcohols, Ethers and Phenols

Lecture 16

Sources of AlcoholsSources of Alcohols

MethanolMethanol is an industrial chemical is an industrial chemical

end uses: solvent, antifreeze, fuelend uses: solvent, antifreeze, fuel

principal use: preparation of formaldehydeprincipal use: preparation of formaldehyde

MethanolMethanolMethanolMethanol

MethanolMethanol is an industrial chemical is an industrial chemical

end uses: solvent, antifreeze, fuelend uses: solvent, antifreeze, fuel

principal use: preparation of formaldehydeprincipal use: preparation of formaldehyde

prepared by hydrogenation of carbon prepared by hydrogenation of carbon monoxidemonoxide

CO + 2HCO + 2H22 CH CH33OHOHCO + 2HCO + 2H22 CH CH33OHOH

MethanolMethanolMethanolMethanol

EthanolEthanol is an industrial chemical is an industrial chemical

Most ethanol comes from fermentationMost ethanol comes from fermentation

Synthetic ethanol is produced by hydrationSynthetic ethanol is produced by hydrationof ethyleneof ethylene

Synthetic ethanol is denatured (madeSynthetic ethanol is denatured (madeunfit for drinking) by adding methanol, benzene,unfit for drinking) by adding methanol, benzene,pyridine, castor oil, gasoline, etc.pyridine, castor oil, gasoline, etc.

EthanolEthanolEthanolEthanol

Isopropyl alcohol is Isopropyl alcohol is prepared by hydration of prepared by hydration of propene.propene.

All alcohols with four carbons or fewer are All alcohols with four carbons or fewer are readily available.readily available.

Most alcohols with five or six carbons are Most alcohols with five or six carbons are readily available.readily available.

Other alcoholsOther alcoholsOther alcoholsOther alcohols

Hydration of alkenesHydration of alkenes

Hydroboration-oxidation of alkenesHydroboration-oxidation of alkenes

Hydrolysis of alkyl halidesHydrolysis of alkyl halides

Syntheses using Syntheses using Grignard reagentsGrignard reagentsorganolithium reagentsorganolithium reagents

Sources of alcoholsSources of alcoholsSources of alcoholsSources of alcohols

Reactions discussed in earlier chaptersReactions discussed in earlier chapters

Reduction of aldehydes and ketonesReduction of aldehydes and ketones

Reduction of carboxylic acidsReduction of carboxylic acids

Reduction of estersReduction of esters

Reaction of Grignard reagents with epoxidesReaction of Grignard reagents with epoxides

Diols by hydroxylation of alkenesDiols by hydroxylation of alkenes

Sources of alcoholsSources of alcoholsSources of alcoholsSources of alcohols

New methods in ChapterNew methods in Chapter

Preparation of AlcoholsPreparation of Alcoholsbyby

Reduction of Aldehydes and KetonesReduction of Aldehydes and Ketones

CC

RR

HH OHOH

HH

CC

RR

HH

OO

Reduction of Aldehydes Gives Primary AlcoholsReduction of Aldehydes Gives Primary AlcoholsReduction of Aldehydes Gives Primary AlcoholsReduction of Aldehydes Gives Primary Alcohols

Pt, ethanolPt, ethanol

(92%)(92%)

Example: Catalytic HydrogenationExample: Catalytic HydrogenationExample: Catalytic HydrogenationExample: Catalytic Hydrogenation

CHCH33OO CHCH22OHOH

OO

CHCH33OO CHCH ++ HH22

CC

RR

HH OHOH

R'R'

CC

RR

R'R'

OO

Reduction of Ketones Gives Secondary AlcoholsReduction of Ketones Gives Secondary AlcoholsReduction of Ketones Gives Secondary AlcoholsReduction of Ketones Gives Secondary Alcohols

(93-95%)(93-95%)

Example: Catalytic HydrogenationExample: Catalytic HydrogenationExample: Catalytic HydrogenationExample: Catalytic Hydrogenation

++ HH22

OO PtPt

ethanolethanol

HH OHOH

SodiumSodiumborohydrideborohydride

LithiumLithiumaluminum hydridealuminum hydride

LiLi++

NaNa++ ––

BB

HH

HH

HHHH––

AlAl

HH

HH

HHHH

Metal Hydride Reducing AgentsMetal Hydride Reducing AgentsMetal Hydride Reducing AgentsMetal Hydride Reducing Agents

act as hydride donorsact as hydride donors

NaBHNaBH44

(82%)(82%)

Examples: Sodium BorohydrideExamples: Sodium BorohydrideExamples: Sodium BorohydrideExamples: Sodium Borohydride

CHCH22OHOH

OO

CHCH

OO22NN methanolmethanol

OO22NN OO

HH OHOH

(84%)(84%)

NaBHNaBH44

ethanolethanol

AldehydeAldehyde

KetoneKetone

Lithium aluminum hydrideLithium aluminum hydrideLithium aluminum hydrideLithium aluminum hydride

more reactive than sodium borohydridemore reactive than sodium borohydride

cannot use water, ethanol, methanol etc.cannot use water, ethanol, methanol etc.as solventsas solvents

diethyl ether is most commonly used solventdiethyl ether is most commonly used solvent

Examples: Lithium Aluminum HydrideExamples: Lithium Aluminum HydrideExamples: Lithium Aluminum HydrideExamples: Lithium Aluminum Hydride

(84%)(84%)

AldehydeAldehyde

KetoneKetone

OO

CHCH33(CH(CH22))55CHCH CHCH33(CH(CH22))55CHCH22OHOH

1. LiAlH1. LiAlH44

diethyl etherdiethyl ether

2. H2. H22OO

OO

(C(C66HH55))22CHCCHCHCCH33

1. LiAlH1. LiAlH44

diethyl etherdiethyl ether

2. H2. H22OO

(86%)(86%)

OHOH

(C(C66HH55))22CHCHCHCHCHCH33

Preparation of DiolsPreparation of Diols

Diols are prepared by...Diols are prepared by...Diols are prepared by...Diols are prepared by...

reactions used to prepare alcoholsreactions used to prepare alcohols

hydroxylation of alkeneshydroxylation of alkenes

OO OO

HCHCCHCH22CHCHCHCH22CH CH

CHCH33

HH22 (100 atm) (100 atm)

Ni, 125°CNi, 125°C

HOCHHOCH22CHCH22CHCHCHCH22CHCH22OHOH

CHCH33

3-Methyl-1,5-pentanediol3-Methyl-1,5-pentanediol

(81-83%)(81-83%)

Example: reduction of a dialdehydeExample: reduction of a dialdehydeExample: reduction of a dialdehydeExample: reduction of a dialdehyde

vicinal diols have hydroxyl groups on adjacent vicinal diols have hydroxyl groups on adjacent carbonscarbons

ethylene glycol (HOCHethylene glycol (HOCH22CHCH22OH) is most familiar OH) is most familiar

exampleexample

Hydroxylation of AlkenesHydroxylation of AlkenesGives Vicinal DiolsGives Vicinal Diols

Hydroxylation of AlkenesHydroxylation of AlkenesGives Vicinal DiolsGives Vicinal Diols

Just for general knowledge, will not be tested on

syn addition of —OH groups to each carbonsyn addition of —OH groups to each carbonof double bondof double bond

Osmium Tetraoxide is Key ReagentOsmium Tetraoxide is Key ReagentOsmium Tetraoxide is Key ReagentOsmium Tetraoxide is Key Reagent

CC CCHHOO OOHH

CC CC

OO OO

OsOs

OOOO

CCCC


(CH(CH33))33COOHCOOHOsOOsO44 (cat) (cat)

tert-tert-Butyl alcoholButyl alcoholHOHO––

Example Example Example Example

(73%)(73%)

CHCH22CHCH33(CH(CH22))77CHCH

CHCH33(CH(CH22))77CHCHCHCH22OHOH

OHOH


Reactions of Alcohols

Review of Reactions of AlcoholsReview of Reactions of AlcoholsReview of Reactions of AlcoholsReview of Reactions of Alcohols

reaction with hydrogen halides reaction with hydrogen halides

acid-catalyzed dehydrationacid-catalyzed dehydration

New Reactions of Alcohols in This ChapterNew Reactions of Alcohols in This ChapterNew Reactions of Alcohols in This ChapterNew Reactions of Alcohols in This Chapter

conversion to ethersconversion to ethers

esterificationesterification

esters of inorganic acidsesters of inorganic acids

oxidationoxidation

cleavage of vicinal diolscleavage of vicinal diols

Conversion of Alcohols to Ethers

RCHRCH22OO

HH

CHCH22RR

OHOH

HH++

RCHRCH22OO CHCH22RR HH OHOH++

Conversion of Alcohols to EthersConversion of Alcohols to EthersConversion of Alcohols to EthersConversion of Alcohols to Ethers

acid-catalyzedacid-catalyzed

referred to as a "condensation"referred to as a "condensation"

equilibrium; most favorable for primary alcoholsequilibrium; most favorable for primary alcohols

ExampleExampleExampleExample

2CH2CH33CHCH22CHCH22CHCH22OHOH

HH22SOSO44, 130°C, 130°C

CHCH33CHCH22CHCH22CHCH22OCHOCH22CHCH22CHCH22CHCH33

(60%)(60%)

Mechanism of Formation of Diethyl EtherMechanism of Formation of Diethyl Ether Mechanism of Formation of Diethyl EtherMechanism of Formation of Diethyl Ether

Step 1:Step 1:Step 1:Step 1:

CHCH33CHCH22OO•••• ••••

HH

HH OSOOSO22OHOH

CHCH33CHCH22OO ••••

HH

OSOOSO22OHOHHH

++––++




CHCH33CHCH22••••

HH

HH

++OO

CHCH33CHCH22OO•••• ••••

HH

++++

CHCH33CHCH22


HH

••••

HH

HH

OO••••




++++

CHCH33CHCH22


HH

OSOOSO22OHOH–– ••••••••

••••

HH OSOOSO22OHOH

••••

••••

CHCH33CHCH22

CHCH33CHCH22OO ••••••••


Ethers

Nomenclature of Ethers, Epoxides

name the groups attached to oxygen in name the groups attached to oxygen in alphabetical order as separate words; "ether" is alphabetical order as separate words; "ether" is last wordlast word

CHCH33OOCHCH2 2 CHCH33

ethylethyl methylmethyl ether ether

CHCH33CHCH22OOCHCH2 2 CHCH33

didiethylethyl ether ether

CHCH33CHCH22OOCHCH22CHCH22CHCH22ClCl

3-chloropropyl3-chloropropyl ethylethyl ether ether

Functional Class IUPAC Names of EthersFunctional Class IUPAC Names of EthersFunctional Class IUPAC Names of EthersFunctional Class IUPAC Names of Ethers

cyclopentyl cyclopentyl methylmethyl sulfide sulfide

analogous to ethers, but replace “ether” as lastanalogous to ethers, but replace “ether” as lastword in the name by “sulfide.”word in the name by “sulfide.”

CHCH33SSCHCH2 2 CHCH33

ethylethyl methyl sulfide methyl sulfide

CHCH33CHCH22SSCHCH2 2 CHCH33

didiethylethyl sulfide sulfide

Functional Class IUPAC Names of SulfidesFunctional Class IUPAC Names of SulfidesFunctional Class IUPAC Names of SulfidesFunctional Class IUPAC Names of Sulfides

SSCHCH33

OxiraneOxirane(Ethylene oxide)(Ethylene oxide)

OxetaneOxetane OxolaneOxolane(tetrahydrofuran)(tetrahydrofuran)

OxaneOxane(tetrahydropyran)(tetrahydropyran)

1,4-Dioxane1,4-Dioxane

Names of Cyclic EthersNames of Cyclic EthersNames of Cyclic EthersNames of Cyclic Ethers OO OO OO

OO

OO

OO


ThiiraneThiirane ThietaneThietane ThiolaneThiolane

ThianeThiane

Names of Cyclic SulfidesNames of Cyclic SulfidesNames of Cyclic SulfidesNames of Cyclic Sulfides SS SS SS

SS


bent geometry at oxygen bent geometry at oxygen analogousanalogous

to water and alcohols, to water and alcohols, i.e.i.e. sp sp3 3 hybidizationhybidization

Structure and Bondingin

Ethers and Epoxides

112°112°

HHOO

HH

105°105° 108.5°108.5°

(CH(CH33))33CCOO

C(CHC(CH33))33

132°132°

HHOO

CHCH33

CHCH33

OOCHCH33

Bond angles at oxygen are sensitiveBond angles at oxygen are sensitiveto steric effectsto steric effects

Bond angles at oxygen are sensitiveBond angles at oxygen are sensitiveto steric effectsto steric effects

most stable conformation of diethyl ethermost stable conformation of diethyl etherresembles pentaneresembles pentane

An oxygen atom affects geometry in much theAn oxygen atom affects geometry in much thesame way as a CHsame way as a CH22 group group

An oxygen atom affects geometry in much theAn oxygen atom affects geometry in much thesame way as a CHsame way as a CH22 group group

Physical Properties of Ethers

boiling pointboiling point

36°C36°C

35°C35°C

117°C117°C

Ethers resemble alkanes more than alcoholsEthers resemble alkanes more than alcoholswith respect to boiling pointwith respect to boiling point

Ethers resemble alkanes more than alcoholsEthers resemble alkanes more than alcoholswith respect to boiling pointwith respect to boiling point

OO OHOH

Intermolecular hydrogenIntermolecular hydrogenbonding possible in bonding possible in alcohols; not possible alcohols; not possible in alkanes or ethers.in alkanes or ethers.

solubility in water (g/100 mL)solubility in water (g/100 mL)

very smallvery small

99

7.57.5

Ethers resemble alcohols more than alkanesEthers resemble alcohols more than alkaneswith respect to solubility in waterwith respect to solubility in water

Ethers resemble alcohols more than alkanesEthers resemble alcohols more than alkaneswith respect to solubility in waterwith respect to solubility in water OO

OHOH

Hydrogen bonding toHydrogen bonding towater possible for etherswater possible for ethersand alcohols; not and alcohols; not possible for alkanes.possible for alkanes.

Lecture 16 - Alcohols, Phenols

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