1. 16.14 Epoxides in Biological Processes

2. Naturally Occurring Epoxides
are common
are involved in numerous biological processes

3. Biosynthesis of EpoxidesC + O2 H+ +
NADH
enzyme C C +
H2O +
NAD+ O
enzyme-catalyzed oxygen transfer from O2 to alkene
enzymes are referred to as monooxygenases

4. Example: biological epoxidation of squalene
O2, NADH monoxygenase O
this reaction is an important step in the biosynthesis of cholesterol

5. 16.15 Preparation of Sulfides

6. prepared by nucleophilic substitution (SN2)
Preparation of RSR'
prepared by nucleophilic substitution (SN2) – ••
• • •• R S R' R S + R' X
NaSCH3
CH3CHCH
CH2 Cl
CH3CHCH
CH2
SCH3
methanol

7. 16.16 Oxidation of Sulfides: Sulfoxides and Sulfones

8. Oxidation of RSR' R S R' O – + O – ++ R S R' R S R' O – sulfide•• R S R' O
• • – + O
• • •• – ++ •• R S R' R S R' O
• • •• –
sulfide
sulfoxide
sulfone
either the sulfoxide or the sulfone can be isolated depending on the oxidizing agent and reaction conditions

9. Sodium metaperiodate oxidizes sulfides to sulfoxides and no further.
Example ••
SCH3 O
• • – + ••
SCH3
NaIO4
water
(91%)
Sodium metaperiodate oxidizes sulfides to sulfoxides and no further.

10. Example
1 equiv of H2O2 or a peroxy acid gives a sulfoxide, 2 equiv give a sulfone ••
SCH
CH2
SCH O
• • •• – ++
CH2
H2O2
(2 equiv)
(74-78%)

11. 16.17 Alkylation of Sulfides: Sulfonium Salts

12. Sulfides can act as nucleophiles+ •• •• R S +
R" X R S
R" X–
• • R' R'
product is a sulfonium salt

13. Example
CH3I +
CH3(CH2)10CH2SCH3
CH3(CH2)10CH2SCH3 I–
CH3

14. Section 16.18 Spectroscopic Analysis of Ethers

15. Infrared Spectroscopy
C—O stretching: and 1150 cm-1 (strong) 6

16. Figure 16.8 Infrared Spectrum of Dipropyl Ether
CH3CH2CH2OCH2CH2CH3
C—O—C
2000
3500
3000
2500
1000
1500
500
Wave number, cm-1
Francis A. Carey, Organic Chemistry, Fourth Edition. Copyright © 2000 The McGraw-Hill Companies, Inc. All rights reserved. 8

17. H—C—O proton is deshielded by O; range is ca. d 3.3-4.0 ppm.
1H NMR
H—C—O proton is deshielded by O; range is ca. d ppm.
d 1.4 ppm
d 0.8 ppm
d 0.8 ppm
CH3 CH2 CH2 OCH2 CH2 CH3
d 3.2 ppm 6

18. Figure 16.9 (page 642) CH3 CH2 CH2 OCH2 CH2 CH3 1
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
Chemical shift (d, ppm) 1

19. Carbons of C—O—C appear in the range d 57-87 ppm.
13C NMR
Carbons of C—O—C appear in the range d ppm.
26.0 ppm O
68.0 ppm

20. UV-VIS
Simple ethers have their absorption maximum at about 185 nm and are transparent to ultraviolet radiation above about 220 nm.

21. Mass Spectrometry
Molecular ion fragments to give oxygen-stabilized carbocation. •+
CH3CH2O
CHCH2CH3
m/z 102 ••
CH3 + +
CH3CH2O CH
CH3CH2O
CHCH2CH3 •• ••
m/z 73
CH3
m/z 87