ethers & epoxides uses galore 1. ethers & epoxides general anesthesia starter fluid...

35
Ethers & Epoxides Uses Galore 1

Upload: thomas-sutton

Post on 18-Jan-2016

230 views

Category:

Documents


2 download

TRANSCRIPT

Page 1: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

1

Ethers & EpoxidesUses Galore

Page 2: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

2

Ethers & Epoxides

General AnesthesiaStarter FluidAntibioticsPheromonesMarijuanaGasoline additivesAntifreezePolyesters

Page 3: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

3

Ethers & Epoxides

R-O-R’Epoxides—cyclic 3-membered ring ethers

Page 4: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

4

Nomenclature of Ethers

Name each alkyl or aryl group in alphabetical order, followed by ether

CH3 OCH3

CH3 O CH3

O

Page 5: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

5

Nomenclature of Ethers

More complex structures require the naming of the –OR group as an alkoxy group. Smaller alkoxy is named as substituent

CH3

CH3

O CH3

OH

O

CH3

O

O

O

CH3

CH3CH3

Page 6: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

6

Physical Properties of Ethers

ColorlessRelatively pleasant odorsLower bp than ROH with equal C’sAlmost same bp as equivalent HCCannot form H-bonds with itselfCan form H-bonds with ROHLow MW soluble in H2OLess dense than H2O

Page 7: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

7

Ethers as Solvents

Relatively inertMakes ethers excellent solventsUsed to extract organic cpds from natural

sourcesMay oxidize over time to peroxides

◦Test papers detect peroxides◦Shaken with FeSO4 reduces peroxides

CH3CH2OCH2CH3 + O2CH3CH2OCHCH3

OOH

Page 8: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

8

The Grignard Reagent: an organometallic compound

Victor Grignard—1912 Nobel in ChemistryWhen Mg turnings (pieces) are stirred with

an ether soln of either alkyl or aryl halide, exothermic rxn occurs

Mg bonds to halogen as does carbon

R—X + Mg R—MgXdry ether

Page 9: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

9

The Grignard Reagent: an organometallic compound

Though ethers are not normally shown as part of the Grignard reagent, they do play an important role as Lewis bases and stabilize the Mg with lone pairs

R—Mg—X

Page 10: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

10

The Grignard Reagent: an organometallic compound

2 most common ethers used in Grignard preparation◦diethyl ether◦tetrahydrofuran (THF)

Ether must be perfectly dry…no H2O or ROH

CH3—I + Mg CH3MgIether

Page 11: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

11

The Grignard Reagent: an organometallic compound

Alkyl or aryl group is usually negatively charged and Mg is positively charged

R—MgXCarbanion is formed

◦Strong base◦Conjugate base of HC(weak acids)◦Grignard reagents react vigorously with weak

acids like H2O or with any cpd with OH, SH, or NH

Page 12: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

12

The Grignard Reagent: an organometallic compound

R—MgX + H—OH R—H + Mg2+(OH)-X-

This is why the ether must be perfectly dry

stronger base stronger acid weaker acid weaker base

MgBr

+ CH3 OH

H

+ CH3 O

MgBr

Page 13: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

13

The Grignard Reagent: an organometallic compound

Rxn of Grignard with H2O can be useful in making a radiolabeled cpd

If heavy water (deuterium oxide), D2O, is used, then D can be substituted for X

CH3 BrM g

e th e rCH3 MgBr

D 2 OCH3 D

Page 14: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

14

The Grignard Reagent: an organometallic compound

Prepare CH3CHDCH3 from CH2=CHCH3

Page 15: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

15

The Grignard Reagent: an organometallic compound

Organometallic cpds contain a C-metal bond

Acetylides (R-C=C-) act similarly to Grignard reagents

Organolithium cpds are also useful in synthesis rxns

R—X + 2 Li R—Li + Li+X-

Page 16: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

16

Preparation of Ethers

Most important ether is diethyl ether◦Made from ethanol and sulfuric acid at 140˚C

If at 180˚C, ethene is made Conditions are important

CH3

OH+ CH3

OH

H 2 S O 4

1 4 0 °CCH3

O

CH3

+ OH2

Page 17: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

17

Preparation of Ethers

The preparation of ethene occurs by E2By what mechanism does the preparation

of diethyl ether occur?

CH3

OH+ CH3

OH

H 2 S O 4

1 4 0 °CCH3

O

CH3

+ OH2

Page 18: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

18

Preparation of Ethers

t-butyl methyl ether (MTBE)Octane # enhancerUse has declined due to health concerns

CH3 OH + CH2

CH3

CH3 H +

CH3 O

CH3

CH3

CH3

Page 19: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

19

Preparation of Ethers

Write the mechanism of the preparation of MTBE.

Page 20: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

20

Preparation of Ethers

Williamson Synthesis◦1st step—ROH is converted to alkoxide by

treatment with reactive metal like Na or K or metal hydride

◦2nd step—SN2 displacement btw alkoxide and alkyl halide

2ROH + 2Na 2RO-Na+ + H2

RO-Na+ + R’—X ROR’ + Na+X-

Page 21: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

21

Preparation of Ethers

Williamson Synthesis◦Write an equation for the synthesis of

CH3OCH2CH2CH3 using Williamson method

Page 22: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

22

Cleavage of Ethers

With lone pair on O, ethers are Lewis bases

React with strong acids, Lewis acids, and boron halides

HR—O—R’ + H+ R—O—R’

R—O—R’ + Br—B—Br R—O—R’ Br Br—B—Br

Br

Page 23: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

23

Cleavage of Ethers

Similar to rxn of ROH and strong acidsIf R and R’ are 1˚or 2˚, bond to O can be

broken by strong nucleophile like I- or Br- via SN2

CH3

O

CH3

CH3

+ HI

CH3

I

+ OH

CH3

CH3

O

CH3

+ BBr3

1 .

2 . H 2 OOH + CH3 Br

Page 24: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

24

Cleavage of Ethers

If R or R’ is 3˚, a strong nucleophile is not required since rxn will occur by SN1 (or E1) mechanism

O

CH3

CH3

CH3

H +

H 2 OOH + CH3

CH3

OHCH3

Page 25: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

25

Cleavage of Ethers

Write the steps of the mechanism for the first rxn on slide 29:CH3

O

CH3

CH3

+ HI

CH3

I

+ OH

CH3

CH3

Page 26: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

26

Ether & Anesthetics

Prior to 1846, asphyxiation, pressure on nerves, narcotics, ROH

William T.G. Morton in 1846 removed tumor from jaw using diethyl ether as general anesthetic

Ceased being used due to flammability, side effects, slow action

Page 27: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

27

Epoxides

Also known as oxiranes◦3-membered rings containing 1 oxygen atom

Most important is ethylene oxide◦Used as raw material for production of ethylene

glycol

O O

H

H

CH3

CH3

O

H

H

CH3

CH3

CH2 CH2 + O2

A g c a ta lys t

2 5 0 °C , p re ssu re O

Page 28: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

28

Gypsy Moth’s Epoxide

Defoliate hardwood treesin NE

Pheromone disparlure

Synthesized to lure male moths to trapsAlternative to pesticide

O

(CH2)9CH3

H

(H3C)2HC(H2C)4

H

Page 29: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

29

Reactions of Epoxides

Much more reactive than ordinary ethers due to the strain on the 3-membered ring

Products will show that ring opens

~8.2 billion lbs of (CH2)2(OH)2 are produced annually in this manner

O+ OH2

H +

OH

OH

Page 30: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

30

Reactions of Epoxides

Show mechanism of previous rxn:

Page 31: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

31

Reactions of Epoxides

Other nucelophiles add in a similar way

Page 32: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

32

Cyclic Ethers

Most common other than epoxides are 5- and 6-membered rings

tetrahydrofuran tetrahydropyran 1,4-dioxane

O O O

O

Page 33: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

33

Cyclic Ethers

THF◦Useful solvent◦Miscible in H2O◦Often superior to diethyl ether for preparation

of Grignard reagents

Page 34: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

34

Cyclic Ethers

Macrocyclic polyethersCrownsForm complexes with Na+, K+ etcAntibiotics are often crown cpds

[18]crown-6

Page 35: Ethers & Epoxides Uses Galore 1. Ethers & Epoxides General Anesthesia Starter Fluid Antibiotics Pheromones Marijuana Gasoline additives Antifreeze Polyesters

35

Cyclic Ethers

Nonactin◦Selectively binds to K+ in presence of Na+

◦Allows for transport of K+ but not Na+