columbia大學(xué)有機化學(xué)課件16_14_18 html

1、16.14Epoxides in Biological Processesare commonare involved in numerous biological processesNaturally Occurring Epoxides+O2+H+CC+NADHenzyme+NAD+CCH2OOenzyme-catalyzed oxygen transfer from O2 to alkene enzymes are referred to as monooxygenasesBiosynthesis of EpoxidesExample:biological epoxidation of

2、squaleneO2, NADHmonoxygenasethis reaction is an important step in the biosynthesis of cholesterolO16.15Preparation of Sulfidesprepared by nucleophilic substitution (SN2)+RXRS RRSNaSCH3methanolCH2CH2CH3CHCHCH3CHCHClSCH3Preparation of RSR16.16Oxidation of Sulfides: Sulfoxides and Sulfones O O+R+RSRRRR

3、SSO sulfonesulfidesulfoxideeither the sulfoxide or the sulfone can be isolated depending on the oxidizing agent and reaction conditionsOxidation of RSR O NaIO4water+SCH3SCH3(91%)Sodium metaperiodate oxidizes sulfides to sulfoxides and no further.Example1 equiv of H2O2 or a peroxy acid gives a sulfox

4、ide, 2 equiv give a sulfone CH2SCH H2O2(2 equiv)O+CH2SCHO (74-78%)Example16.17Alkylation of Sulfides: Sulfonium Salts+R+XRS RRSXRRproduct is a sulfonium saltSulfides can act as nucleophiles+ CH3(CH2)10CH2SCH3CH3ICH3(CH2)10CH2SCH3ICH3ExampleSection 16.18Spectroscopic Analysis of EthersCO stretching:1

5、070 and 1150 cm-1 (strong)Infrared SpectroscopyFigure 16.8Infrared Spectrum of Dipropyl Ether350030002500200015001000500Wave number, cm-1Francis A. Carey, Organic Chemistry, Fourth Edition. Copyright 2000 The McGraw-Hill Companies, Inc. All rights reserved.CH3CH2CH2OCH2CH2CH3COCHCO proton is deshiel

6、ded by O;ca. d 3.3-4.0 ppm.range isd 1.4 ppmd 0.8 ppmd 0.8 ppmCH3 CH2 CH2 OCH2 CH2 CH3d 3.2 ppm1H NMRFigure 16.9 (page 642)CH3 CH2 CH2 OCH2 CH2 CH310.09.08.07.06.05.04.03.02.01.00Chemical shift (d, ppm)Carbons of COC appear in the range d 57-87 ppm.26.0 ppm68.0 ppmO13C NMRSimple ethers have their absorption maximum at about 185 nm and are transparent to ultraviolet radiation above about 220 nm.UV-VISMolecular ion fragments to give oxygen-