厦门大学化学化工学院：《有机化学》课程教学资源（课件讲稿，双语版）第九章 核磁共振谱和质谱（9.1-9.9）Introduction

Chapter 9 Nuclear Magnetic Resonance andE Mass Spectrometry: Too or Structure, Determinat 抗谱和质谱

Chapter 9 Nuclear Magnetic Resonance and Mass Spectrometry: Tools for Structure Determination 核磁共振谱和质谱

ORGANIC CHEMISTRY Chapter 9 9.1 Introduction Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.1 Introduction

ORGANIC CHEMISTRY Chapter 9 g How are molecular structures determined? One o way Is though the use of spectroscopic methods Spectroscopy is the study of the interaction of energy with matter o When energy is applied to matter it can be absorbed emitted cause a chemical change or be transmitted o Nuclear magnetic resonance(NMR) spectrometry -energy absorption by molecules that have been placed in a strong magnetic field o Mass spectrometry(MS)-molecular structure robed by bombarding molecules with a beam of high energy electrons Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 How are molecular structures determined? One way is though the use of spectroscopic methods. Spectroscopy is the study of the interaction of energy with matter. When energy is applied to matter it can be absorbed, emitted, cause a chemical change, or be transmitted. Nuclear magnetic resonance (NMR) spectrometry –energy absorption by molecules that have been placed in a strong magnetic field. Mass spectrometry (MS) — molecular structure probed by bombarding molecules with a beam of high energy electrons

ORGANIC CHEMISTRY Chapter 9 9.2 The Electromagnetic Spectrum Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.2 The Electromagnetic Spectrum

ORGANIC CHEMISTRY Chapter 9 o Electromagnetic radiation is one type of energy e=h hc o NMR involves absorption of energy in the radiofrequency range Highe Lowest waelenst ium IINO 10 Gamma I ray X viole Infrared Radio frequency iN 60O 7 751 VIsible region Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 Electromagnetic radiation is one type of energy. E = hv = hcλ NMR involves absorption of energy in the radiofrequency range

ORGANIC CHEMISTRY Chapter 9 9.3 Nuclear Magnetic Resonance Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.3 Nuclear Magnetic Resonance

ORGANIC CHEMISTRY Chapter 9 g Nuclei with an odd mass or odd atomic number have nuclear spin"(in a similar fashion to the spin of electrons ) This includes H and 3C(but not 2C) o The nuclei of protons (h)and carbon-13(C),and certain other elements and isotopes, behave as if they were tiny bar magnets g When placed in a magnetic field and irradiated with radio frequency energy these nuclei absorb energy at frequencies based on their chemical environments o nmr spectrometers are used to measure these absorptions Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 Nuclei with an odd mass or odd atomic number have "nuclear spin" (in a similar fashion to the spin of electrons). This includes 1H and 13C (but not 12C). The nuclei of protons (1H) and carbon-13 (13C), and certain other elements and isotopes, behave as if they were tiny bar magnets When placed in a magnetic field and irradiated with radio frequency energy, these nuclei absorb energy at frequencies based on their chemical environments NMR spectrometers are used to measure these absorptions

ORGANIC CHEMISTRY Chapter 9 9.3A Sweep(CW) NMr Spectrometers NMR spectrometers can be designed so that irradiate the compound with electromagnetic energy of a constant frequency while the magnetic field strength is varied(扫场) or swept(扫频) Ho Sample tube ka lio freguency utput input spectrum Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.3A Sweep (CW) NMR Spectrometers NMR spectrometers can be designed so that irradiate the compound with electromagnetic energy of a constant frequency while the magnetic field strength is varied (扫场)or swept(扫频)

ORGANIC CHEMISTRY Chapter 9 9.3B Fourier Transform(FT) NMR Spetrometer o The sample is placed in a constant (and usually very strong) magnetic field o The sample is irradiated with a short pulse of radio frequency energy that excites nuclei in different environments all at once o The resulting signal contains information about all of the absorbing nuclei at once This signal is converted to a spectrum by a Fourier transformation o FT NMR allows signal-averaging which leads to enhancement of real spectral signals versus noise Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.3B Fourier Transform (FT) NMR Spetrometers The sample is placed in a constant (and usually very strong) magnetic field The sample is irradiated with a short pulse of radio frequency energy that excites nuclei in different environments all at once The resulting signal contains information about all of the absorbing nuclei at once This signal is converted to a spectrum by a Fourier transformation FT NMR allows signal-averaging, which leads to enhancement of real spectral signals versus noise

ORGANIC CHEMISTRY Chapter 9 Superconducting magnet Precessing Free induction (cooled by liquid helium nucleus decay Fourier transform Time requency pulse domain domain The radio frequency excitation pulse and resulting NMR signals are sent through cables between the probe coils in the magnet and the computer Radio frequency (Rf) generator and computer operating console Sample tube spins within the Fourier transformation of the signal probe coils in the hollow bore from the time domain to the frequency at the center of the magnet domain occurs at the computer console Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9