columbia大学有机化学课件17_17 html

1、Section 17.17 Spectroscopic Analysis ofAldehydes and KetonesPresence of a C=O group is readily apparent in infrared spectrumC=O stretching gives an intense absorption at 1710-1750 cm-1In addition to peak for C=O, aldehydes give two weak peaks near 2720 and 2820 nm for HC=OInfrared SpectroscopyFigure

2、 17.13Infrared Spectrum of Butanal350030002500200015001000500Wave number, cm-1Francis A. Carey, Organic Chemistry, Fourth Edition. Copyright 2000 The McGraw-Hill Companies, Inc. All rights reserved.HC=OCH3CH2CH2CH=OC=OAldehydes:HC=O proton is at very low field(d 9-10 ppm).CH3 singlet near d 2 ppm.Me

3、thyl ketones:1H NMRFigure 17.1410.09.08.07.06.05.04.03.02.01.00Chemical shift (d, ppm)OHCCH(CH3)2Figure 17.15OCCH3CH2CH310.09.08.07.06.05.04.03.02.01.00Chemical shift (d, ppm)Carbonyl carbon is at extremely low field-neard 200 ppmIntensity of carbonyl carbon is usually weak13C NMRFigure 17.16C200180

4、160140120100806040200Chemical shift (d, ppm)O H3CH2CCH2CH2CH2CH3Aldehydes and ketones have two bands in the UV region:p p* and n p*p p*:excitation of a bonding p electron toan antibonding p * orbitalp p*:excitation of a nonbonding electronon oxygen to an antibonding p * orbitalUV-VISH3Cp p*n p*l187 nm270 nm maxCOlmaxH3CUV-VISMolecular ion fragments to give an acyl catio