alcohol 1023

• Hydroxyl (OH) functional group ( ROH )• Oxygen is sp3 hybridized • Polar molecule why…….? == > (Oxygen have 2 lone pairs)

1.Primary alcohol: Carbon with –OH is bonded to one other carbon.

H H H C– C– OH or CH3CH2 OH or R CH2 OH H H2.Secondary alcohol: Carbon with –OH is bonded to two other carbons. H H H C–--- C– OH or CH3 C H OH or R – CH OH H H C H H CH3 R

3. Tertiary alcohol: Carbon with –OH is bonded to three other carbons. H CH3 R H H C H H C------ C– OH or CH3 C --- OH or R – C -- OH H H C H H CH3 R

4.Aromatic (phenol): -OH is bonded to a benzene ring. OH

CH3 CH

CH3

CH2OH

CH3 C

CH3

CH3

OHOH

CH3 CH

OH

CH2CH3

Primary (1o) Secondary (2o)

Tertiary (3o) Aromatic (phenol)

CH3CH2CH2OH

4-penten-2-ol (old)

pent-4-ene-2-ol (1997 revision of IUPAC rules)

CH2 CHCH2CHCH3

OH

1.Find the longest carbon chain containing the carbon with the -OH group.

2. Drop the -e from the alkane name, add -ol.3. Number the chain, starting from the end

closest to the -OH group.4.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

Naming Priority

• Acids• Esters• Aldehydes• Ketones• Alcohols• Amines

• Alkenes• Alkynes• Alkanes• Ethers• Halides

• When -OH is part of a higher priority class of compound, it is named as hydroxy.

• Example:

CH2CH2CH2COOH

OH

4-hydroxybutanoic acid

• Alcohol can be named as alkyl alcohol.

• Useful only for small alkyl groups.

• Examples:

CH3 CH

CH3

CH2OH CH3 CH

OH

CH2CH3

isobutyl alcohol sec-butyl alcohol

Naming Diols

• Two numbers are needed to locate the two -OH groups.

• Use -diol as suffix instead of -ol.

HO OH

1,6-hexanediol

Glycols

• 1, 2 diols (vicinal diols) are called glycols.• 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 glycol

1,2-propanediol

propylene glycol

• -OH group is assumed to be on carbon 1.• For common names of disubstituted phenols,

use ortho- for 1,2; meta- for 1,3; and para- for 1,4.

• Methyl phenols are cresols.OH

Cl

3-chlorophenol

meta-chlorophenol

OH

H3C

4-methylphenol

para-cresol

1. Boiling point of alcohol

2. Solubility of alcohol

3. Acidity of alcohol

i) Higher compared to corresponding alkane.. Why?

ii) Unusually high boiling points due to hydrogen bonding between molecules

alcohol M.p B.p Density• Methanol -97 65 0.792• Ethanol -114 78 0.789• Propan-1-ol - 126 97 0.804• Propan-2-ol - 88 82 0.786• Butan-1-ol - 90 118 0.810• 2-methylpropan-1-ol -118 108 0.802• Butan-2-ol -114 100 0.808• 2,2-dimethylethanol 25 83 0.789• Pentan-1-ol - 79 138 0.817• Hexan-1-ol - 52 158 0.819

Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases

Solubility decreases as the size of the alkyl group increases.

• pKa range: 15.5-18.0 (water: 15.7)• pKa … ?• Acidity decreases as alkyl group

increases.• Halogens increase the acidity.• Phenol is 100 million times more acidic

than cyclohexanol!

Table of Ka Values

CH3 OH

React methanol and ethanol with sodium metal (redox reaction).

CH3CH2OH + Na CH3CH2O Na + 1/2 H2

React less acidic alcohols with more reactive potassium.

+ K (CH3)3CO K + 1/2 H2)3C OH(CH3

1. Manufactured preparation of alcohol

2. Lab preparation of alcohol

i) Grignard reagents

ii ) Reduction of aldehyde/ketones

iii) Hydrolysis of alkyl halide

iv) Hydration of alkenes

Preparation of Methanol :

By passing (execess) hydrogen and carbon monoxide over chromium (III) oxide/Zinc Oxide as catalyst at 350- 400o C

Cr2O3/ZnO cat

2H2 + CO ============ > CH3OH

350-400 oC high preesure

• Preparation of Ethanol :

• By direct hydrolysis of ethylene.

• Mixture of C2H4 and water vapour passed over phosphoric acid 300oC 68-70 atm pressure

phosphoric acid

• C2H4 + H2O ======== > CH3CH2OH

• 300 oC 68-70 atm

• Fermentation:

• Diastase

• 2(C6H10O5)n + nH2O == > n C12H22O11

• 60 o C maltose• Maltase

• C12H22O11 + H2O === > C6H12O6

Glucose

Zymase

• C6H12O6 === > 2CH3CH2OH + 2CO2

• ethanol

1. Grignard Reaction (RMgX) H ether H H2O H

C=O + RMgMX == > H C–OMgX ==> H C OH + MgXOH

H R dil acid R

Formaldehyde 1o alcohol

R1 ether H H

C=O + RMgMX == > R1 C–OMgX ==> R1 C OH + MgXOH

H R R

Acetaldehyde 2o Aocohol

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

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

R2 ether R2 R2

C=O + RMgMX == > R1 C–OMgX ==> R1 C OH + MgXOH

R1 R R

Acetone 3o Aocohol

Grignard Reaction (RMgX)

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

Some Grignard ReagentsBr

+ Mgether MgBr

CH3CHCH2CH3

Clether

+ Mg CH3CHCH2CH3

MgCl

CH3C CH2

Br + Mgether

CH3C CH2

MgBr

R1 LiAlH4

C=O == == > R1 CH2OH

H Ether

Acetaldehyde 1o Aocohol

R1 LiAlH4

C=O == == > R1 CHOH

R Ether R

Aacetone 2o Aocohol

Since LiALH4 is strong reduction agent, other reduction agent such as:

LiBH4 ( in Ether )

NaBH4(In Ethanol/H2O)

Also can be used.

Comparison of Reducing Agents

• LiAlH4 is stronger.

• LiAlH4 reduces more stable compounds which are resistant to reduction.

1. Hydrolysis (substitution) of OH- on alkyl halide

CH3CH2X + HOH ===>CH3CH2OH + HX

• 2.Hydration of alkenes

H2C=CH2 + H2O == > CH3CH2OH

1. Dehydration to alkene2. Oxidation to aldehyde, ketone3. Substitution to form alkyl halide4. Reduction to alkane5. Esterification6. Williamson synthesis of ether

1. Conc. H2SO4 produces alkene

2. Carbocation intermediate

3. Saytzeff product

4. Bimolecular dehydration produces ether

5. Reaction condition:

Low temp, 140°C and below, favors ether

High temp, 180°C and above, favors alkene

CH3CHCH3

OHH2SO4

alcoholCH3CHCH3

OH

H

CH3CHCH3

CH2 CHCH3H2O

CH3OH

H3O+

CH3OH CH3 OH2 CH3 O

H

CH3

H2OCH3OCH3

• 1° alcohol to aldehyde to carboxylic acid• Difficult to stop at aldehyde• Use pyridinium chlorochromate (PCC) to limit the

oxidation.• PCC can also be used to oxidize 2° alcohols to

ketones.

CH3CH2CH2CH2

OH N H CrO3Cl

CH3CH2CH2CH

O

CH3CHCH2CH3

OHNa2Cr2O7 / H2SO4

CH3CCH2CH3

O

=>

1. 2° alcohol becomes a ketone2. Reagent is Na2Cr2O7/H2SO4

3. Active reagent probably H2CrO4

4. Color change: orange to greenish-blue

Example

• Cannot lose 2 H’s

• Basis for chromic acid test

=>

• Collins reagent: Cr2O3 in pyridine

• Jones reagent: chromic acid in acetone

• KMnO4 (strong oxidizer)

• Con. Nitric acid (strong oxidizer)

• CuO, 300°C (industrial dehydrogenation). =>

• Dehydrate with conc. H2SO4, then add H2

• Tosylate, then reduce with LiAlH4

CH3CHCH3

OHH2SO4

CH2 CHCH3H2

PtCH3CH2CH3

alcohol alkene alkane

alcohol

CH3CHCH3

OHTsCl

CH3CHCH3

OTsLiAlH4

alkane

CH3CH2CH3

tosylate

=>

• -OH of alcohol is protonated

• -OH2+ is good leaving group

• 3° and 2° alcohols react with Br- via SN1

• 1° alcohols react via SN2

H3O+

Br-

R O H R O H

H

R Br =>

• Chloride is a weaker nucleophile than bromide.

• Add ZnCl2, which bonds strongly with -OH, to promote the reaction.

• The chloride product is insoluble.

• Lucas test: ZnCl2 in conc. HCl– 1° alcohols react slowly or not at all.– 2 alcohols react in 1-5 minutes.– 3 alcohols react in less than 1 minute.

• HI does not react• Poor yields of 1° and 2° chlorides• May get alkene instead of alkyl halide• Carbocation intermediate may rearrange.

• Good yields with 1° and 2° alcohols

• PCl3 for alkyl chloride (but SOCl2 better)

• PBr3 for alkyl bromide

• P and I2 for alkyl iodide (PI3 not stable)

=>

• P bonds to -OH as Br- leaves

• Br- attacks backside (SN2)

• HOPBr2 leaves

• Produces alkyl chloride, SO2, HCl

• S bonds to -OH, Cl- leaves

• Cl- abstracts H+ from OH

• C-O bond breaks as Cl- transferred to C

• Fischer: alcohol + carboxylic acid

• Tosylate esters

• Sulfate esters

• Nitrate esters

• Phosphate esters

Can be carried out by following methods

• Acid + Alcohol yields Ester + Water

• Sulfuric acid is a catalyst.

• Each step is reversible.

CH3 C OH

O

+ CH2CH2CHCH3

CH3

OHH

+

CH3C

O

OCH2CH2CHCH3

CH3

+ HOH

Sulfate Esters

Alcohol + Sulfuric Acid

+HO S

O

O

OH H O CH2CH3H

+

OCH2CH3

O

O

SHO

CH3CH2O H + OCH2CH3

O

O

SHOH

+

CH3CH2O S

O

O

OCH2CH3

Nitrate Esters

+ H O CH2CH3H

+

N OH

O

OOCH2CH3N

O

O

CH2

CH2

CH2

O H

O H

O H

+ 3 HO NO2

CH2

CH2

CH2

O NO2

O NO2

O NO2

nitroglycerineglycerine =>

Phosphate Esters

P

O

OH

OH

HOCH3OH

P

O

OH

OH

CH3OCH3OH

P

O

OCH3

OH

CH3O

P

O

OCH3

OCH3

CH3O

CH3OH

=>

• ROH + Na (or NaH) yields sodium alkoxide• RO- + 1° alkyl halide yields ether (Williamson

ether synthesis)

CH3CH2CHCH3

O

CH3CH2 Br+ CH2CH2CH

CH3

O CH2CH3

=>

Acid Catalyst

CH3-CH2 OH == > CH2=CH2+ H2O Acid Catalyst

• CH3CH –CH2 == > CH3CH2=CH2 + H2O

H OH

1. Solvent

2. Sources of other materials

=>

C2H5OH

R-COOC2H5 C2H5NH2

Starh, Sugar, Cellulose C2H5Cl

C2H4

C2H5HSO4

C2H5OC2H5

CHI3C2H5ONa CH3COOH

CH3CHOZn +Acid / LiAlH4 (reduction)

Boil with

KOH

SOl 2, P

Cl 5 or H

Cl

Excess acid K2 Cr

2 O7 (Oxidation)

Yeast

(Fer

men

tatio

n)H

NO

2

I 2 +

Na 2

CO

3 so

ln

Iodo

form

test

c H 2SO 4 (l

ow temp )

Exces

s Alco

hol +

con

H 2SO 4

140

o C

Warm with

H 2O

RCOOH Esterification

Heat with KOH soln

(hydrolysis)

Vapour + Air (Ag at 600 o C) (Oxid )

Preparation Substitution Reaction

He

at

with

C2H

5O

H

c H

2SO

4

He

at

17

0o C

– H

2O

Na

dil acids LiAlH

4 (reduction) - H

2O

Methanol• “Wood alcohol”

• Industrial production from synthesis gas

• Common industrial solvent

• Fuel at Indianapolis 500– Fire can be extinguished with water– High octane rating– Low emissions– But, lower energy content– Invisible flame =>

Ethanol

• Fermentation of sugar and starches in grains• 12-15% alcohol, then yeast cells die.• Distillation produces “hard” liquors• Azeotrope: 95% ethanol, constant boiling• Denatured alcohol used as solvent• Gasahol: 10% ethanol in gasoline• Toxic dose: 200 mL ethanol, 100 mL methanol

=>

2-Propanol

• “Rubbing alcohol”

• Catalytic hydration of propene

=>

CH2 CH CH2 H2O100-300 atm, 300°C

catalyst+ CH3 CH

OH

CH3

Formation of Phenoxide Ion

Phenol reacts with hydroxide ions to form phenoxide ions - no redox is necessary.

O H

+ OH

O

+ HOH

pKa = 10pKa = 15.7

=>

Glycols (Review)

• Syn hydroxylation of alkenes– osmium tetroxide, hydrogen peroxide– cold, dilute, basic potassium permanganate

• Anti hydroxylation of alkenes– peroxyacids, hydrolysis

Organometallic Reagents

• Carbon is bonded to a metal (Mg or Li).

• Carbon is nucleophilic (partially negative).

• It will attack a partially positive carbon.– C - X– C = O

• A new carbon-carbon bond forms. =>

Organolithium Reagents

• Formula R-Li (reacts like R:- +Li)

• Can be produced from alkyl, vinyl, or aryl halides, just like Grignard reagents.

• Ether not necessary, wide variety of solvents can be used.

=>

Reaction with Carbonyl

• R:- attacks the partially positive carbon in the carbonyl.

• The intermediate is an alkoxide ion.• Addition of water or dilute acid protonates the

alkoxide to produce an alcohol.

RC O R C O

HOHR C OH

OH=>

How would you synthesize…

CH3CH2CHCH2CH2CH3

OH CH2OH

OH

CH3C

OH

CH2CH3

CH3 =>

Grignard and Ester (1)

• Grignard attacks the carbonyl.

• Alkoxide ion leaves! ? !

C OCH3O

H3C

MgBrR MgBr C

CH3

OCH3

OR

C

CH3

OCH3

OR MgBr C

CH3

RO

+ MgBrOCH3

Ketone intermediate =>

Second step of reaction

• Second mole of Grignard reacts with the ketone intermediate to form an alkoxide ion.

• Alkoxide ion is protonated with dilute acid.

C

CH3

RO

R MgBr + C

CH3

R

OR MgBr

HOH

C

CH3

R

OHR

=>

How would you synthesize...

CH3CH2CCH3

OH

CH3

C

OH

CH3

Using an acid chloride or ester.

CH3CH2CHCH2CH3

OH

=>

Grignard Reagent + Ethylene Oxide

• Epoxides are unusually reactive ethers.

• Product is a 1º alcohol with 2 additional carbons.

MgBr + CH2 CH2

OCH2CH2

O MgBr

HOH

CH2CH2

O H

=>

Limitations of Grignard

• No water or other acidic protons like O-H, N-H, S-H, or -C—C-H. Grignard reagent is destroyed, becomes an alkane.

• No other electrophilic multiple bonds, like C=N, C—N, S=O, or N=O.

=>

Reduction of Carbonyl

• Reduction of aldehyde yields 1º alcohol.• Reduction of ketone yields 2º alcohol.• Reagents:

– Sodium borohydride, NaBH4

– Lithium aluminum hydride, LiAlH4

– Raney nickel

=>

Sodium Borohydride

• Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion.

• Then the alkoxide ion is protonated by dilute acid.

• 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

• Stronger reducing agent than sodium borohydride, but dangerous to work with.

• Converts esters and acids to 1º alcohols.

CO

OCH3C

OH H

HH3O+

LAH =>

Catalytic Hydrogenation

• Add H2 with Raney nickel catalyst.

• Also reduces any C=C bonds.

O

H2, Raney Ni

OH

NaBH4

OH

=>

Thiols (Mercaptans)

• Sulfur analogues of alcohols, -SH.

• Named by adding -thiol to alkane name.

• The -SH group is called mercapto.

• Complex with heavy metals: Hg, As, Au.

• More acidic than alcohols, react with NaOH to form thiolate ion.

• Stinks! =>

Thiol Synthesis

Use a large excess of sodium hydrosulfide with unhindered alkyl halide to prevent dialkylation to R-S-R.

H S_

R X R SH +_

X

=>

Thiol Oxidation

• Easily oxidized to disulfides, an important feature of protein structure.

R SH + RHSBr2

Zn, HClR S S R + 2 HBr

• Vigorous oxidation with KMnO4, HNO3, or NaOCl, produces sulfonic acids.

SHHNO3

boilS

O

O

OH

=>

Biological Oxidation

• Catalyzed by ADH, alcohol dehydrogenase.• Oxidizing agent is NAD+, nicotinamide

adenine dinucleotide.• Ethanol oxidizes to acetaldehyde, then acetic

acid, a normal metabolite.• Methanol oxidizes to formaldehyde, then

formic acid, more toxic than methanol.• Ethylene glycol oxidizes to oxalic acid, toxic.• Treatment for poisoning is excess ethanol.

=>

Unique Reactions of Diols

• Pinacol rearrangement• Periodic acid cleavage

=>

Pinacol Rearrangement• Pinacol: 2,3-dimethyl-2,3-butanediol

• Dehydration with sulfuric acid

CH3 C

CH3

OH OH

CH3

C CH3H

+

CH3 C

CH3

OH OH

CH3

C CH3

H

CH3 C

CH3

OH

CCH3

CH3

CH3 C

CH3

OH

CCH3

CH3CH3 C

OH

CH3

C CH3

CH3

CH3 C

OH

CH3

C CH3

CH3

CH3 C

O

CH3

C CH3

CH3

pinacolone

=>

Periodic Cleavage of Glycols

Same products formed as from ozonolysis of the corresponding alkene.

CH3 C

H

OH OH

CH3

C CH3

HIO4CH3 C

H

O+ C

OCH3

CH3

C CH3C

H CH3

CH3

OsO4

H2O2

O3

(CH3)2S

=>

Oxidation States

• Reagents used:

CrO42- reduced to Cr2O3

KMnO4 reduced to MnO2

• Oxidation: loss of H2, gain of O, O2, or X2

• Reduction: gain of H2 or H-, loss of O, O2, or X2

• Neither: gain or loss of H+, H2O, HX =>