CHE 242 Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER TEN Terrence P. Sherlock Burlington.

CHE 242Unit V

Structure and Reactions of Alcohols, Ethers and

Epoxides; Basic Principles of NMR Spectroscopy

CHAPTER TEN

Terrence P. Sherlock

Burlington County College

2004

Chapter 10 2

Classify these:

CH3 CH

CH3

CH2OH CH3 C

CH3

CH3

OH

OH

CH3 CH

OH

CH2CH3 =>

Chapter 10 3

Name these:

CH3 CH

CH3

CH2OH

CH3 C

CH3

CH3

OH

CH3 CH

OH

CH2CH32-methyl-1-propanol

2-methyl-2-propanol

2-butanol

OH

Br CH3

3-bromo-3-methylcyclohexanol =>

Chapter 10 4

Naming Priority

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

• Alkenes• Alkynes• Alkanes• Ethers• Halides

=>

Chapter 10 5

Hydroxy Substituent

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

• Example:

CH2CH2CH2COOH

OH

4-hydroxybutanoic acid

also known as GHB

=>

Chapter 10 6

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 =>

Chapter 10 7

Naming Phenols

• -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-methylphenolpara-cresol =>

Chapter 10 8

Physical Properties

• Unusually high boiling points due to hydrogen bonding between molecules.

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

=>

Chapter 10 9

Boiling Points

=>

Chapter 10 10

Solubility in Water

Solubility decreases as the size of the alkyl group increases.

=>

Chapter 10 11

Acidity of Alcohols

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

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

than cyclohexanol!

=>

Chapter 10 12

Table of Ka Values

=>

CH3 OH

Chapter 10 13

Formation of Alkoxide Ions

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

=>

Chapter 10 14

Formation of Phenoxide Ion

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

O H

+ OH

O

+ HOH

pK a = 10pK a = 15.7

=>

Chapter 10 15

Synthesis (Review)

• Nucleophilic substitution of OH- on alkyl halide

• Hydration of alkeneswater in acid solution (not very effective)oxymercuration - demercurationhydroboration - oxidation

=>

Chapter 10 16

Glycols (Review)

• Syn hydroxylation of alkenesosmium tetroxide, hydrogen peroxidecold, dilute, basic potassium

permanganate

• Anti hydroxylation of alkenesperoxyacids, hydrolysis

=>

Chapter 10 17

Organometallic Reagents

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

• Carbon is nucleophilic (partially negative).

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

• A new carbon-carbon bond forms. =>

Chapter 10 18

Grignard Reagents

• Formula R-Mg-X (reacts like R:- +MgX)• Stabilized by anhydrous ether• Iodides most reactive• May be formed from any halide

primarysecondarytertiaryvinylaryl =>

Chapter 10 19

Some Grignard Reagents

Br

+ Mgether MgBr

CH3CHCH2CH3

Clether

+ Mg CH3CHCH2CH3

MgCl

CH3C CH2

Br + Mgether

CH3C CH2

MgBr =>

Chapter 10 20

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.

=>

Chapter 10 21

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=>

Chapter 10 22

Synthesis of 1° Alcohols

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

=>

Chapter 10 23

Synthesis of 2º Alcohols

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

=>

Chapter 10 24

Synthesis of 3º Alcohols

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

=>

Chapter 10 25

How would you synthesize…

CH3CH2CHCH2CH2CH3

OH CH2OH

OH

CH3C

OH

CH2CH3

CH3 =>

Chapter 10 26

Grignard Reactions with Acid Chlorides

and Esters• Use two moles of Grignard reagent.

• The product is a tertiary alcohol with two identical alkyl groups.

• Reaction with one mole of Grignard reagent produces a ketone intermediate, which reacts with the second mole of Grignard reagent. =>

Chapter 10 27

Grignard + Acid Chloride (1)

C OCl

H3C

MgBrR MgBr C

CH3

Cl

OR

C

CH3

Cl

OR MgBr C

CH3

RO

+ MgBrCl

Ketone intermediate =>

• Grignard attacks the carbonyl.• Chloride ion leaves.

Chapter 10 28

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 =>

Chapter 10 29

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

=>

Chapter 10 30

How would you synthesize...

CH3CH2CCH3

OH

CH3

C

OH

CH3

Using an acid chloride or ester.

CH3CH2CHCH2CH3

OH

=>

Chapter 10 31

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

=>

Chapter 10 32

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.

=>

Chapter 10 33

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

=>

Chapter 10 34

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+

=>

Chapter 10 35

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 =>

Chapter 10 36

Comparison of Reducing Agents

• LiAlH4 is stronger.

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

Chapter 10 37

Catalytic Hydrogenation

• Add H2 with Raney nickel catalyst.

• Also reduces any C=C bonds.

O

H2, Raney Ni

OH

NaBH4

OH

=>

Chapter 10 38

POWER POINT IMAGES FROM “ORGANIC CHEMISTRY, 5TH EDITION”

L.G. WADEALL MATERIALS USED WITH PERMISSION OF AUTHOR

PRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGEORGANIC CHEMISTRY COURSE

BY:ANNALICIA POEHLER STEFANIE LAYMAN CALY MARTIN