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1、16.14Epoxides in Biological Processes,are common are involved in numerous biological processes,Naturally Occurring Epoxides,enzyme-catalyzed oxygen transfer from O2 to alkene enzymes are referred to as monooxygenases,Biosynthesis of Epoxides,+,+,C,C,O,NADH,H2O,+,NAD+,enzyme,this reaction is an impor
2、tant step in the biosynthesisof cholesterol,Example: biological epoxidation of squalene,O2, NADHmonoxygenase,16.15Preparation of Sulfides,prepared by nucleophilic substitution (SN2),Preparation of RSR,+,S,R,NaSCH3,methanol,16.16Oxidation of Sulfides:Sulfoxides and Sulfones,either the sulfoxide or th
3、e sulfone can be isolated depending on the oxidizing agent and reactionconditions,Oxidation of RSR,R,S,R,+,sulfide,sulfoxide,sulfone,Example,Sodium metaperiodate oxidizes sulfides to sulfoxides and no further.,(91%),water,Example,H2O2,1 equiv of H2O2 or a peroxy acid gives a sulfoxide, 2 equiv give
4、a sulfone,(74-78%),(2 equiv),16.17Alkylation of Sulfides:Sulfonium Salts,product is a sulfonium salt,Sulfides can act as nucleophiles,+,R,X,S,R,R,S,R,R,R,+,X,Example,CH3(CH2)10CH2SCH3,CH3I,CH3(CH2)10CH2SCH3,CH3,+,I,Section 16.18Spectroscopic Analysis of Ethers,CO stretching: 1070 and 1150 cm-1 (stro
5、ng),Infrared Spectroscopy,Francis A. Carey, Organic Chemistry, Fourth Edition. Copyright 2000 The McGraw-Hill Companies, Inc. All rights reserved.,Wave number, cm-1,Figure 16.8 Infrared Spectrum of Dipropyl Ether,COC,CH3CH2CH2OCH2CH2CH3,HCO proton is deshielded by O; range isca. d 3.3-4.0 ppm.,1H NM
6、R,CH3 CH2 CH2 OCH2 CH2 CH3,d 0.8 ppm,d 0.8 ppm,d 1.4 ppm,d 3.2 ppm,Chemical shift (d, ppm),CH3 CH2 CH2 OCH2 CH2 CH3,Figure 16.9 (page 642),68.0 ppm,Carbons of COC appearin the range d 57-87 ppm.,26.0 ppm,13C NMR,Simple ethers have their absorption maximum at about 185 nm and are transparent to ultraviolet radiation above about 220 nm.,UV-VIS,Molecular ion fragments to give oxygen-stabilizedcarbocation.,m/z 102,CH3CH2O,CHCH2CH3,CH3,CH3CH2O,+,CH,CH3,CH3CH2O,+,CHCH2CH3,m/z 87,m/z 73,Mass Spectrometry,+,
