主要内容 一、天然产物有效成分提取方法的原理 ——溶剂提取法与水蒸气蒸馏法的原理、操作及其特点 二、天然产物有效成分分离与精制 ——天然产物有效成分各种分离方法的原理 三、化合物的纯度测定 四、结构研究的主要程序 五、结构研究中采用的主要方法—— UV IR MS NMR

Chemists use spectroscopy (Ir, UV-Vis, NMR) to determine molecular structure. spectroscopy: technique that measures the amount of radiation a substance absorbs at various wavelengths(based on the quantization of molecular energy levels Molecules exist in quantized energy states (rotational, vibrational, and electronic quantum states) Molecules absorb discrete amounts of energy(ae)and are excited to higher

3. 1 Chemical shift When an atom is placed in a magnetic field B its electrons circulate about the direction of the applied magnetic field. This circulation causes a small magnetic field at the nucleus which opposes the externally applied field The magnetic field at the nucleus(the effective field) is therefore generally less than the applied field by a fraction THNMR

nature publishing group http://structbio.nature.com news and views Department of Biological Sciences. chem.276146-116200 Columbia University, New York, New York 6. Chen,.. Sharma, 5. Quiocho, F.A. Davidson. A.L. 15. Jones. P.M. George. A.M. FEMS Microbiol. Lett

Introduction NMR is the most powerful tool available for organic structure determination. It is used to study a wide variety of nuclei:

一、自旋偶合与自旋裂分 spin coupling and spin splitting 二、峰裂分数与峰面积 number of pear splitting and pear areas 三、磁等同与磁不等同 magnetically equivalent and 第三节 nonequivalent 自旋偶合与自旋裂分 nuclear magnetic

将自旋核放入磁场中,用适宜频率的电磁 波照射,它们会吸收能量,发生原子核能 级的跃迁,同时产生核磁共振信号,得到 核磁共振谱,这种方法称为核磁共振波谱 法。(NMR, nuclear magnetic resonance spectroscopy）

核磁共振 核磁共振(NMR)就是指处于某个静磁场中的物质的原子核系统受到相应频率的电 磁辐射时,在它们的磁能级之间发生的共振跃迁现象。它自问世以来已在物理、化学、 生物、医学等方面获得广泛应用,是测定原子的核磁矩和研究核结构的直接而准确的方 法,也是精确测量磁场的重要方法之一

一、核磁共振与化学位移 nuclear magnetic resonance and chemical shift 二、影响化学位移的因素 factors influenced chemical shift

一、原子核的自旋 atomic nuclear spin 二、核磁共振现象 nuclear magnetic resonance 三、核磁共振条件 condition of nuclear magnetic resonance 四、核磁共振波谱仪 nuclear magnetic resonance spectrometer