chapter 10 structure and synthesis of alcohols l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 10 Structure and Synthesis of Alcohols PowerPoint Presentation
Download Presentation
Chapter 10 Structure and Synthesis of Alcohols

Loading in 2 Seconds...

play fullscreen
1 / 50

Chapter 10 Structure and Synthesis of Alcohols - PowerPoint PPT Presentation


  • 317 Views
  • Uploaded on

Organic Chemistry , 5 th Edition L. G. Wade, Jr. Chapter 10 Structure and Synthesis of Alcohols. Jo Blackburn Richland College, Dallas, TX Dallas County Community College District ã 2003, Prentice Hall. Structure of Alcohols. Hydroxyl (OH) functional group

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 10 Structure and Synthesis of Alcohols' - arleen


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 10 structure and synthesis of alcohols

Organic Chemistry, 5th EditionL. G. Wade, Jr.

Chapter 10Structure and Synthesis of Alcohols

Jo Blackburn

Richland College, Dallas, TX

Dallas County Community College District

ã 2003,Prentice Hall

structure of alcohols
Structure of Alcohols
  • Hydroxyl (OH) functional group
  • Oxygen is sp3 hybridized. =>

Chapter 10

classification
Classification
  • Primary: carbon with –OH is bonded to one other carbon.
  • Secondary: carbon with –OH is bonded to two other carbons.
  • Tertiary: carbon with –OH is bonded to three other carbons.
  • Aromatic (phenol): -OH is bonded to a benzene ring.=>

Chapter 10

iupac nomenclature
IUPAC Nomenclature
  • Find the longest carbon chain containing the carbon with the -OH group.
  • Drop the -e from the alkane name, add -ol.
  • Number the chain, starting from the end closest to the -OH group.
  • Number and name all substituents. =>

Chapter 10

name these
Name these:

2-methyl-1-propanol

2-butanol

2-methyl-2-propanol

3-bromo-3-methylcyclohexanol =>

Chapter 10

unsaturated alcohols
Unsaturated Alcohols
  • Hydroxyl group takes precedence. Assign that carbon the lowest number.
  • Use alkene or alkyne name.

4-penten-2-ol (old)

pent-4-ene-2-ol

(1997 revision of IUPAC rules) =>

Chapter 10

naming priority
Acids

Esters

Aldehydes

Ketones

Alcohols

Amines

Alkenes

Alkynes

Alkanes

Ethers

Halides =>

Naming Priority

Chapter 10

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

also known as GHB =>

4-hydroxybutanoic acid

Chapter 10

common names
Common Names
  • Alcohol can be named as alkyl alcohol.
  • Useful only for small alkyl groups.
  • Examples:

isobutyl alcohol

sec-butyl alcohol

=>

Chapter 10

naming diols
Naming Diols
  • Two numbers are needed to locate the two -OH groups.
  • Use -diol as suffix instead of -ol.

1,6-hexanediol =>

Chapter 10

glycols
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

=>

ethylene glycol

Chapter 10

naming phenols
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

=>

3-chlorophenol

meta-chlorophenol

Chapter 10

physical properties
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

methanol
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 =>

Chapter 10

ethanol
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 =>

Chapter 10

2 propanol

=>

2-Propanol
  • “Rubbing alcohol”
  • Catalytic hydration of propene

Chapter 10

acidity of alcohols
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

table of k a values
Table of Ka Values

=>

Chapter 10

formation of alkoxide ions

=>

Formation of Alkoxide Ions

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

React less acidic alcohols with more

reactive potassium.

Chapter 10

formation of phenoxide ion
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

=>

Chapter 10

synthesis review
Synthesis (Review)
  • Nucleophilic substitution of OH- on alkyl halide
  • Hydration of alkenes
    • water in acid solution (not very effective)
    • oxymercuration - demercuration
    • hydroboration - oxidation =>

Chapter 10

glycols review
Glycols (Review)
  • Syn hydroxylation of alkenes
    • osmium tetroxide, hydrogen peroxide
    • cold, dilute, basic potassium permanganate
  • Anti hydroxylation of alkenes
    • peroxyacids, hydrolysis =>

Chapter 10

organometallic reagents
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. =>

Chapter 10

grignard reagents
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 =>

Chapter 10

organolithium reagents
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

reaction with carbonyl

=>

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.

Chapter 10

synthesis of 1 alcohols

=>

Synthesis of 1° Alcohols

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

Chapter 10

synthesis of 2 alcohols

=>

Synthesis of 2º Alcohols

Grignard + aldehyde yields a secondary alcohol.

Chapter 10

synthesis of 3 alcohols

=>

Synthesis of 3º Alcohols

Grignard + ketone yields a tertiary alcohol.

Chapter 10

grignard reactions with acid chlorides and esters
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

grignard acid chloride 1
Grignard + Acid Chloride (1)
  • Grignard attacks the carbonyl.
  • Chloride ion leaves.

Ketone intermediate =>

Chapter 10

grignard and ester 1
Grignard and Ester (1)
  • Grignard attacks the carbonyl.
  • Alkoxide ion leaves! ? !

Ketone intermediate =>

Chapter 10

second step of reaction

=>

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.

Chapter 10

how would you synthesize39

=>

How would you synthesize...

Using an acid chloride or ester.

Chapter 10

grignard reagent ethylene oxide

=>

Grignard Reagent + Ethylene Oxide
  • Epoxides are unusually reactive ethers.
  • Product is a 1º alcohol with 2 additional carbons.

Chapter 10

limitations of grignard
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

reduction of carbonyl
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

sodium borohydride

=>

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.

Chapter 10

lithium aluminum hydride

=>

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

Chapter 10

comparison of reducing agents
Comparison of Reducing Agents
  • LiAlH4 is stronger.
  • LiAlH4 reduces more stable compounds which are resistant to reduction. =>

Chapter 10

catalytic hydrogenation

=>

Catalytic Hydrogenation
  • Add H2 with Raney nickel catalyst.
  • Also reduces any C=C bonds.

Chapter 10

thiols mercaptans
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! =>

Chapter 10

thiol synthesis

=>

Thiol Synthesis

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

Chapter 10

thiol oxidation

=>

Thiol Oxidation
  • Easily oxidized to disulfides, an important feature of protein structure.
  • Vigorous oxidation with KMnO4, HNO3, or NaOCl, produces sulfonic acids.

Chapter 10