CHE 242 Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER TEN

1
CHE 242Unit VStructure and Reactions of
Alcohols, Ethers and Epoxides Basic Principles
of NMR SpectroscopyCHAPTER TEN

• Terrence P. Sherlock
• Burlington County College
• 2004

2
Classify these
3
Name these
2-methyl-1-propanol
2-butanol
2-methyl-2-propanol
3-bromo-3-methylcyclohexanol
gt
4
Naming Priority

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

• Alkenes
• Alkynes
• Alkanes
• Ethers
• Halides gt

5
Hydroxy Substituent

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

also known as GHB
gt
4-hydroxybutanoic acid
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.

1,2-ethanediol
1,2-propanediol
propylene glycol
gt
ethylene glycol
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.

4-methylphenol
para-cresol gt
3-chlorophenol
meta-chlorophenol
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.
  gt

9
Boiling Points
10
Solubility in Water
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!
  gt

12
Table of Ka Values
gt
13
Formation of Alkoxide Ions

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

React less acidic alcohols with more reactive
potassium.
14
Formation of Phenoxide Ion

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

O
O
H
O
H







H
O
H
p
K



1
5
.
7
a
p
K



1
0
a
gt
15
Synthesis (Review)

• Nucleophilic substitution of OH- on alkyl halide
• Hydration of alkenes
• water in acid solution (not very effective)
• oxymercuration - demercuration
• hydroboration - oxidation
  gt

16
Glycols (Review)

• Syn hydroxylation of alkenes
• osmium tetroxide, hydrogen peroxide
• cold, dilute, basic potassium permanganate
• Anti hydroxylation of alkenes
• peroxyacids, hydrolysis
  gt

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 - X
• C O
• A new carbon-carbon bond forms.
  gt

18
Grignard Reagents

• Formula R-Mg-X (reacts like R- MgX)
• Stabilized by anhydrous ether
• Iodides most reactive
• May be formed from any halide
• primary
• secondary
• tertiary
• vinyl
• aryl
  gt

19
Some Grignard Reagents
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.
  gt

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.

22
Synthesis of 1 Alcohols

• Grignard formaldehyde yields a primary alcohol
  with one additional carbon.

23
Synthesis of 2º Alcohols

• Grignard aldehyde yields a secondary alcohol.

24
Synthesis of 3º Alcohols

• Grignard ketone yields a tertiary alcohol.

25
How would you synthesize
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.
  gt

27
Grignard Acid Chloride (1)

• Grignard attacks the carbonyl.
• Chloride ion leaves.

Ketone intermediate gt
28
Grignard and Ester (1)

• Grignard attacks the carbonyl.
• Alkoxide ion leaves! ? !

Ketone intermediate gt
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.

30
How would you synthesize...

• Using an acid chloride or ester.

31
Grignard Reagent Ethylene Oxide

• Epoxides are unusually reactive ethers.
• Product is a 1º alcohol with 2 additional carbons.

32
Limitations of Grignard

• No water or other acidic protons like O-H, N-H,
  S-H, or -CC-H. Grignard reagent is destroyed,
  becomes an alkane.
• No other electrophilic multiple bonds, like CN,
  CN, SO, or NO.
  gt

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
  gt

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.

35
Lithium Aluminum Hydride

• Stronger reducing agent than sodium borohydride,
  but dangerous to work with.
• Converts esters and acids to 1º alcohols.

36
Comparison of Reducing Agents

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

37
Catalytic Hydrogenation

• Add H2 with Raney nickel catalyst.
• Also reduces any CC bonds.

38
POWER POINT IMAGES FROM ORGANIC CHEMISTRY, 5TH
EDITIONL.G. WADEALL MATERIALS USED WITH
PERMISSION OF AUTHORPRESENTATION ADAPTED FOR
BURLINGTON COUNTY COLLEGEORGANIC CHEMISTRY
COURSEBYANNALICIA POEHLER STEFANIE LAYMAN
CALY MARTIN