Alcohols• Contain a hydroxyl (-OH) group

RO

H +

−

• Intermolecular forces: dipole-dipole, H-bonding• H-bonds between alcohol molecules: high boiling points

• H-bonds with water: up to 4-carbon alcohols soluble in water

• -OH group can act as a weak base or a weak acid

R OH R O

H

H

R O + Strong acid + Strong base

H3CO

H

H3CO

H

HO

H

alkoxide oxonium ionalcohol

Alcohol Nomenclature• Parent chain = longest chain containing C with -OH

• Root name: replace –e with –ol• ethane ethanol, butene butenol, etc.

• Give –OH the smallest possible number• –OH has priority over double bonds, alkyl groups

• Two –OH groups -diol; three –OH groups -triol– Add to end of root name (propane propanediol)

OH

5-methyl-3-hexanol

OHHO

1,2-ethanediol(ethylene glycol)

antifreeze

Alcohol Naming Practice

OH

OH

OH

OH

OH

2-propanol

(isopropyl alcohol)2,4-dimethyl-3-pentanol

4-penten-2-ol3,5-dimethyl-2,4-heptanediol

Classes of Alcohols

Primary (1°) alcohol

Secondary (2°) alcohol

Tertiary (3°) alcohol

OH

OH

OH

CH3

1-butanol

4-phenyl-2-hexanol

1-methylcyclohexanol

OH C attached to 1 other C

OH C attached to 2 other C’s

OH C attached to 3 other C’s

Reactions of Alcohols• Reaction with strong bases

– alcohol as proton donor (weak acid)

• Reaction with strong acids– alcohol as proton acceptor (weak base)

• Dehydration– reverse of hydration of alkenes

– requires H+ catalyst

• Oxidation– increase # of C-O bonds

R OH R O

H

H

R O

Strong acid

Strong base

alkoxide

oxonium ion

R OH

- H2O

alkene

H C C CH3

OH

H

H

H

C C

CH3

HH

H

R R'

O

R H

O

aldehyde ketone

orR OH

oxidizing agent

H+

Dehydration MechanismStep 1: electrophilic H+ catalyst attacks nucleophilic O atom

Step 2: H2O dissociates, leaving behind a carbocation

Step 3: Electrons from neighboring C-H bond form bond, regenerating H+ catalyst

H2O+H C C CH3

O

H

H

H

HH

H C C

H

H

CH3

H

H C C

H

H

CH3

HC C

CH3

HH

H

H+

H C C CH3

O

H

H

H

HH

H C C CH3

OH

H

H

H

H

Hydration and Dehydration

C C

CH3

HH

H

H2O+ H C C CH3

OH

H

H

H

H+

Hydration and dehydration are in equilibrium

Can change [H2O] to favor one reaction or the other

Change Favors

Increase [H2O] Formation of Alcohol (hydration)

Decrease [H2O] Formation of Alkene (dehydration)

Possible Dehydration Products

The most-substituted alkene product is favored (most stable)

OH

H

OH

H

OHH

OHH+

?

Majorproduct

Least H’s on double bond

Oxidation of Alcohols• Oxidation: increases oxidation number

– More C-O bonds (add O) or increases bond order– Fewer C-H bonds (remove H)

• Needs an oxidizing agent– CrO3, Cr2O7

2-, MnO4-

1° alcohol

RC

H

O

RC

OH

OC OHR

H

H

aldehyde carboxylic acid

PCC stops ataldehyde

oxidizingagent

oxidizingagent

+1

+1

-1-2

+1

+1

-2 -2

-2+3+1

+1

0

0 0

CrO3

(Cr6+)Cr3+

,or PCC (pyridinium chlorochromate)

Breathalyzer Tests

ethanol ethanal(acetaldehyde)

ethanoic acid(acetic acid)

CH3 C OH

H

H

CH3 C

H

O

CH3 C

OH

O

+ Cr6+ + Cr3+

oxidized oxidized

Breathalyzer Tests

ethanol ethanal(acetaldehyde)

ethanoic acid(acetic acid)

CH3 C OH

H

H

CH3 C

H

O

CH3 C

OH

O

+ Cr6+ + Cr3+

oxidized oxidized

methanol methanal(formaldehyde)

methanoic acid(formic acid)

H C OH

H

H

H C

H

O

H C

OH

Ooxidized oxidized

RC

R

OC OHR

H

R

Oxidation of Alcohols

2° alcohol

ketone

oxidizingagent

C OHR

R

R

3° alcohol oxidizingagent No reaction

-2+1

0

-2

+20

0

0 0

+1

CH3 C

CH3

O

CH3 C OH

CH3

H

2-propanol propanone(acetone)

Reaction of Alcohols with Hydrogen Halides

1° alcohols react via the SN2 reaction mechanism:

C OH + HX C X + H2O

2° and 3° alcohols react via SN1 reaction mechanism:

C C OH + HX C C X + H2O

C C

Reaction of Alcohols with Hydrogen Halides

CH3OH + HBr CH3Br + H2O

CH3CHCH3 + HCl CH3CHCH3 + H2O

OH Cl

Cl

O

Naming aldehydes and ketonesParent chain = longest chain containing C=O (carbonyl)

Aldehyde KetonePrefix

Suffix

Numbering

Naming Priority: Aldehydes > Ketones > Alcohols

-OH (alcohol) substituent → “hydroxy”

oxo

–e becomes –al

C=O is always C #1

(don’t have to number it)

oxo

–e becomes –one

C=O is lowest possible number

(must number it)

H

OOH

3-hydroxy-4-methylpentanal 3-chloro-2-butanone

Naming Practice

OO

O O

O O

propanedial 2,4-pentanedione

3-oxopentanal

Has both an aldehyde and a

ketone

Aldehyde has priority

Ketone = oxo

Condensation of Alcohols

Condensation reaction: two molecules combine to form a larger molecule (+ water)– Catalyzed by acid (H+)

CH3−OH H-O−CH3

H2SO4

catalystCH3−O−CH3 + H2O+

alcohol alcohol ether water+ +

Ethers

• Intermolecular forces:

– Dipole-dipole

– No H-bonding between ether molecules• Lower boiling point than alcohols

– Water or alcohols can H-bond to ether oxygen• Somewhat soluble in water and other polar solvents

RO

RR

OH

HO

Hwater

alcohol

− H-bond acceptor

No H-bond donor

Two alkyl groups (C’s) bound to oxygen

Naming Ethers• Common names: name both R groups, add “ether”

diethyl ether(anesthetic)

Oethyl ethyl

Naming Ethers• Common names: name both R groups, add “ether”

diethyl ether(anesthetic)

tert-butyl methyl ether(used as gasoline additive)

propyl people etherO

O O

O

♫ “one-eyed, one-horned, flying...” ♪

methyltert-butyl

ethyl ethyl

OCH3

propyl

O

OO

H

Reactions of Ethers

• Reactions of peroxides: Explosive!

• Formation of peroxides

diisopropyl ether peroxide

Controlleddetonation

Resulting crater:3 feet wide,

one foot deep

+ O2

peroxide

O

diisopropyl ether

RC

H

O

RC

R'

O

Aldehydes and Ketones

• C=O group called a carbonyl group

C and O bothsp2 hybridized

120°120°

aldehyde ketone

RC

H

O

+

−

RC

H

O Very polar C=O bond• Higher boiling point than alkanes

H-bond acceptor• Soluble in polar solvents

No H-bond donor• Lower boiling point than alcohols

Structural Isomers

• Draw all the possible structural isomers for the following formulas:

C4H10O

C5H12O

C4H8O

C5H10O

Alcohols and Ethers

Aldehydes and Ketones

(contain a double bond)

Notice that all formulas contain one oxygen

What functional groups do you know that contain one oxygen?

Does the atom ratio of carbon to hydrogen make a difference?

C4H10O Isomers

OHOH

OHOH

OO

O

1-butanol 2-butanol

2-methyl-2-propanol 2-methyl-1-propanol

diethyl ether methyl propyl ether isopropyl methyl ether

C5H12O Isomers

OHOH

OH

OH

OH

OHOH

OH

1-pentanol 2-pentanol 3-pentanol

2-methyl-1-butanol 3-methyl-2-butanol 3-methyl-1-butanol

2-methyl-2-butanol 2,2-dimethyl-1-propanol

C5H12O Isomers

O O O

OOO

butyl methyl ether tert-butyl methyl ether sec-butyl methyl ether

isobutyl methyl ether ethyl propyl ether ethyl isopropyl ether

C4H8O Isomers

O

O

O

butanal 2-butanone

2-methylpropanal

C5H10O Isomers

OO

O

O

O

O

O

pentanal 2-pentanone 3-pentanone

3-methylbutanal 3-methyl-2-butanone

2,2-dimethylpropanal 2-methylbutanal

Reactions of Aldehydes and Ketones• Oxidation of aldehydes to carboxylic acids

– CrO3, MnO4-

• Reduction of aldehydes and ketones to alcohols– Decrease C-O bonds, increase C-H bonds

– Reducing agents: LiAlH4, NaBH4, H2/Pt

OHH

O

propanal 1-propanol

CH3−CH2−CHO CH3−CH2−CH2−OH

LiAlH4

O OH

NaBH4

2-methyl-3-pentanone 2-methyl-3-pentanol

Reduction of Aldehydes/Ketones

O

O OH

OH

O

3-oxopentanal 1,3-pentanediol

LiAlH4

NaBH4

cyclohexanone cyclohexanol

H2/Pt

OH

OO OH OH

pentanedial 1,5-pentanediol

Carboxylic Acid Nomenclature

• Parent chain: longest containing carboxyl group (COOH)

• Name of parent: replace “–e” with “–oic acid”

• Numbering starts at carboxyl carbon– Priority: Carboxylic acid > aldehydes > ketones > alcohols

“hydroxy”

substituent“oxo”

substituents

OH

O

trans-3-methyl-2-hexenoic acid(human armpits)

OH

O O

3-oxobutanoic acid(diabetes)

HO OH

O O

propanedioic acid(apples)

R C

O

O H

O

OHO

O

aspirin

OH

HN O

CH3

Tylenol

Can irritate your stomach Gentle on the stomach

A carboxylic acid Just an alcohol

Carboxylic Acid Reactions

• Reduction to 1° alcohols– Only LiAlH4 reduces carboxylic acids

(not NaBH4 or H2/Pt)

butanoic acid 1-butanolOHOH

O LiAlH4

butanoic acid

OH

O NaBH4

or H2/PtNO RXN

OH

O

Reactant remains unchanged

What are the products?

3-oxo-4-pentenoic acid

LiAlH4

H2/Pt NaBH4

OH

OOH

OH

OO

OH

OOH

OH

OH

3-hydroxypentanoic acid

4-pentene-1,3-diol

3-hydroxy-4-pentenoic acid