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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 under each peak relative ratios of different protons; 3. Splitting of each signalnumber of vicinal prot
