有机化学双语版++Spectroscopy.ppt

1、Chapter 11 Spectroscopy（波谱）,11.1 Introduction (A) The instrumental Methods of structure determination to organic compounds (B) Property of electromagnetic radiation (C) Relationship between the molecular structure and absorption spectrum 11.2 Infrared spectroscopy (A) Infrared Spectroscopy (IR) (B)

2、Modes of molecular vibrations (C) Factors to affect frequency of molecular stretching vibration and its location in an IR spectrum,(D) Treatment of the sample (E) Interpreting of IR spectra 11.3 Nuclear Magnetic Resonance (NMR) Spectroscopy 11.4 Shielding and deshielding of protons 11.5 The chemical

3、 shift 11.5.1 The chemical shift 11.5.2 The relation of molecular structure with 1H chemical shift 11.5.3 Interpretting 1H NMR spectra Diastereotopic hydrogens Enantiotopic hydrogens,11.6 Signal splitting: spin-spin coupling Coupling constant nJab Splitting role (n + 1)role Reciprocity of coupling c

4、onstants Splitting patterns 11.7 13C NMR Spectroscopy 11.7.1 Introduction The function of 13C NMR The great advantage of 13C spectroscopy Decoupling techniques 11.7.2 13C chemical shifts The factors that most affect 13C chemical shifts,(A) The principal instrumental methods of structure determinatio

5、n to organic compounds,Nuclear Magnetic Resonance Spectroscopy 核磁共振谱,Infrared Spetroscopy 红外光谱,IR,Key functional groups,Ultraviolet-Visible Spectroscopy 紫外可见光谱,UV-VIS,Electron distribution in the Mole. With Conjugated systems,Mass Spectrometry 质谱,MS,Molecular weight and Formula of the mole. and the

6、structure units in it.,1. Carbon skeleton 2. The Environments of the hydrogens atta- ched to carbon or other atoms,NMR,(B) Property of electromagnetic radiation:,E= h = hc/ h Planck s constant: 6.63 10-34 J. s Frequency( Hz), = c Wavelength (nm) c The speed of light: 3 10 8 m. s-1 The wave counts /c

7、m,The properties of both particles and waves,The greater the frequency, the shorter the wavelength; The shorter the wavelength, the higher the energy.,Ch.P153,h = E = E2 - E1,(C) Relationship between the structure of Mole. and absorption spectrum:,Electronic energyUV-VIS Vibrational energy IR The sp

8、in states of an atomic nucleusNMR,11.2 Infrared spectroscopy (IR),Function of Infrared Spectroscopy:,Identifying the presence of certain functional groups in the molecules.,Electromagnetic spectrum,Electromagnetic radiation:,The compound absorb IR energy to cause the change of vibrational energy sta

9、tes of the covalent bond in the mole.,Ch.P154,B. Modes of molecular vibrations,Biatomic molecule,Triatomic molecule,An in-plane bending vibration,An out-of-plane bending vibration,A stretching vibration,Symmetric stretching,Asymmetric stretching,(C) Factors affecting frequency of molecular stretchin

10、g vibration and its location in an IR spectrum,1. The masses of the bonded atoms:,Light atoms vibrate at higher frequencies,2. The relative stiffness of the bond (键的刚性）,(D) Treatment of the sample:,Neat sample: pure liquid between two NaCl disks Solid: mixed with KBr and pressed into a thin wafer So

11、lution: CCl4, chloroform as solvent,(E) Interpreting of IR spectra:,16004000 cm-1 The region in which vibrations of functional groups,1300625 cm-1 Fingerprint region,Characteristic absorptions of the compounds,Ch.P519,Table 1 Infrared Absorption Frequencies of Some Common Structural Units,Stretching

12、 vibrations,Bending vibrations of diagnostic value,CH3(CH2)6CH3,2960cm-1 2930cm-1 1467cm-1 1380cm-1,ArH (stretch),CH ( bending),Toluene,2-Methyl-2-propanol,OH (stretch),(E)-2-己烯,(Z)-3-己烯,2-甲基-1-丙烯,1-己炔,2-己炔,Essential condition of NMR:,The different Nuclei, the different E,11.3 Nuclear Magnetic Reson

13、ance （NMR） Spectroscopy,The spinning atomic nuclei: 1H, 13C (I= 12),Process of Nuclear Magnetic Resonance,Schematic operation of an NMR spectrometer,At the proton, the induced magnetic field opposes The external magnetic field,11.4 Shielding and deshielding of protons,Heffect = H0 - Hin,11.5.1 The c

14、hemical shift,The shift of absorption signal of proton by shielding and deshileding effect.,Reference compound: (CH3)4Si, TMS,The chemical shift is expressed in hertz,The chemical shift is different with different external magnetic field strengths.,Independent of the field strength,ppm: part per mil

15、lion 百万分之一,11.5.2 Relation of molecular structure with 1H chemical shifts:,Different environments of protons in the mole., different degrees of shielding in the experiment, different chemical shifts.,Increased shielding of methyl protons Decreasing electronegativity of attached atom,Aromatic protons

16、 are in the deshielding region.,11.5.3 Intepreting proton NMR spectra (氢谱的解析),Information about the mole. Structure by 1H NMR spectra:,The induced magnetic field of theelectrons of an arene reinforces the applied fields.,磁各向异性效应,The number of signalsthe kind of proton; 2. Intergration of the area un

17、der each peak relative ratios of different protons; 3. Splitting of each signalnumber of vicinal protons to that one.,Ch.P164,CH3OCH2CN,Chemical nonequivalent,H1:H2 2:3,How many signals on NMR spectra?,Diastereotopic 非对映异构,Enantiotopic hydrogen:,Enantiomers,CH2Br: The same ,Geminal protons,Ch. P165:

18、 Table 7-4,P424 Tab.13.3,1H NMR: can be in the range of 1-10 ppm,P423,11.6 Signal splitting: spin-spin coupling,CHCl2CH2Cl,The phenomenon of signal splitting is spin-spin splitting.,Singnal from the proton of Ha in the absence of Hb,Magnetic moments of Hb split the signal from Ha into two peaks of e

19、qual intensity, a 1:1 doublet.,Signal splitting,The protons on neighboring atoms,Magnetic fields,The interaction of the nuclear Spins of neighboring atoms is called spin-spin coupling.,nJabcoupling constant(Hz),Distance,Independence of the field strength.,3JHH = 7.5Hz,Vicinal coupling,Signal splitti

20、ng is not observed for protons:,Chemically equivalent protons,2. Enantiotopic protons,3. Separated by more than three bonds,CH3CH3,Singlet Doublet Triplet Quartet,1:1 1:2:1 1:3:3:1,Multiple Broad: complex OH,When protons have the same chemical shifts, no signal splitting,Two groups of protons couple

21、d to each other have the same coupling constant J.,(proton of Hb split the signal into 1:3:3:1quartet),Multiplicity of signal for Ha = n + 1:,n quivalent protons on neighboring atoms,split a signal into n + 1 peaks.,(signal in the absence of protons Hb),Splitting role (n + 1)role :,P425, Ch.P165,CH3

22、CH2Br,Reciprocity of coupling constants,Integration: 2:2:3,Problem 1. Describe the appearance of the 1H NMR spectrum,Isopropyl chloride,1H NMR(CDCl3) ,1.52 (d, J = 3.5Hz, 6H, CH3),4.2(m,1H,CHCl),Signals may overlap:,Splitting patterns,A. Doublet:,Nonequivalent vicinal protons, / J 6,First order spec

23、trum: (n+1), / J 6,B. Two bond coupling,Geminal protons,Diastereotopic,Different chemical shifts,doublet,doublet,2J = 2Hz,1-Chloro-1-cyanoethene,C. Complex Splitting,Doublet of doublet :dd,trans,cis,J trans Jcis,13C NMR spectrum directly provide the information about carbon skeleton of a molecule.,C

24、lCH2CH2CH2CH2CH3,1H NMR 4 Signals,The natural abundance: 1 H 99.985% 13C 1.1% 12C 99%,Carbon isotopes,Pulse FT techniques (脉冲 傅立叶变换技术),Routine tool,The function of 13C NMR,P430 13.12,13C NMR 5 Signals,The great advantage of 13C spectroscopy,R,: 1H spectra: 3 ppm 13C spectra: 8090 ppm,Peaks arising from all the carbon atoms.,(2) Signals are less likely to overlap.,13C spectra were further simplified,Spin-spin coupling between the carbon nuclei could be not seen.,(1) The wide range of chemical shifts,1H N