有机光谱化学分析 (18).pdf

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1、P1:Hello everyone,welcome to this class-organic spectroscopic analysis.P1：大家好，欢迎学习今天的课程有机波谱分析。P2:In the previous class,we have learned the concept-chemical shift.The first picture of chemical shift is showing here.The three peaks of ethyl alcohol were observed in 1951 at Stanford University.P2：在上一课中

2、，我们学习了化学位移的概念。这是化学位移的第一张图片。1951 年，斯坦福大学观察到了乙醇的三个峰。P3:In NMR spectrum,shift in frequency,due to the shielding by electrons,is called the chemical shift.P3：在 NMR 谱中，由于电子的屏蔽而导致的频率偏移称为化学位移。P4:This difference will also depend on the strength of the applied magnetic field,B0.The greater the value of B0,th

3、e greater the frequency difference.This relation could make it difficult to compare NMR spectra taken on spectrometers operating at different field strengths.P4：该差异还将取决于外加的磁场强度 B0。B0的值越大，频率差越大。这种关系可能使比较在不同场强下运行的仪器上获得的 NMR 谱图变得困难。P5:For example here,the resonance frequency of two types of nuclei in t

4、he methanol molecule differ.P5：例如，甲醇分子中两种核的共振频率不同。P6:Therefore,the location of an NMR signal in a spectrum is to be reported relative to a reference signal from a standard compound added to the sample.P6：因此，谱图中 NMR 信号为添加到样品中标准化合物的参考信号的相对值。P7:The chemical shift is caused by the opposing magnetic fiel

5、d generated by electrons around nuclear.Therefore,any factor that changes the density of the nuclear electron cloud can affect the chemical shift.The influencing factors include Electronegativity,Anisotropy,Conjugation Effect,Hydrogen Bonding,Steric Effect,Solvent Effect etc.P7：化学位移是由核外电子云产生的与外磁场相反感

6、生磁场引起的。因此，任何改变核外电子云密度的因素都会影响化学位移。影响因素包括电负性，各向异性，共轭效应，氢键，立体效应，溶剂效应等。P8:When the electronegativity of the element connected to the proton is stronger,its electron withdrawing effect is stronger.Electron deviates from the proton.The shielding effect weakens.P8：与质子连接的元素的电负性越强，则其吸电子效应越强。电子偏离质子。屏蔽效应减弱。P9:

7、How does electronegativity influence chemical shift?The greater the electronegativity is,the greater the chemical shift is.P9：电负性如何影响化学位移？电负性越大，化学位移越大。P10:As for anisotropic effect,valence electrons generate an induced magnetic field.electrons of the double bond form an electron circulation induced

8、by the applied magnetic field,resulting in a secondary magnetic field.P10：对于各向异性效应，价电子会产生感应磁场。双键的电子产生由外磁场引起的电子环流，从而产生次级（感应）磁场。The different regions in the molecule can be divided into shielding region and deshielding region.The shielding area is the region in which the induced magnetic field is oppo

9、site to the external magnetic field direction.分子中的不同区域可分为屏蔽区域和去屏蔽区域。屏蔽区域是感应磁场与外部磁场方向相反的区域。The deshielding area is the region in which the induced magnetic field is the same as the external magnetic field direction.While the hydrogen on the double bond is in the deshielding region,the absorption peak

10、 appears in the downfield.of alkenes is 4.55.7,hydrogen on aldehydesis 9.410.去屏蔽区域是感应磁场与外部磁场方向相同的区域。当双键上的氢处于屏蔽区域时，吸收峰出现在低场中。烯烃的为 4.55.7，醛氢为 9.410。P11:The valence electron generates an induced magnetic field.The electrons of the triple bond are symmetrically distributed around the bond axis.Under the

11、 induction of an external magnetic field,the electrons can form an electron circulation around the bond axis,thereby generating a secondary magnetic field.Along the bond axis,it is the shielding area,and the direction vertical to the bond axis is the deshielding area.P11：价电子产生感应磁场。三键的电子围绕键轴对称分布。在外部磁

12、场的感应下，电子可以形成围绕键合轴的电子环流，从而产生次生感应磁场。沿着键轴的方向是屏蔽区域，垂直于键轴的方向是去屏蔽区域。P12:The six electrons on the benzene ring generate a strong induced magnetic field.Above and below the double bond region,it forms two electronic circulations under the action of an external magnetic field,generating a secondary magnetic

13、field.The electron cloud density is high above and below the benzene ring plane,forming a shielding area.The electron cloud density on each side of the ring plane is low,forming a deshielding area.P12：苯环上的六个电子产生强感应磁场。在双键区域的上方和下方，在外部磁场的作用下形成两组电子环流，从而产生感应磁场。在苯环平面的上方和下方，电子云密度很高，从而形成了屏蔽区域。环形平面的侧边电子云密度低，

14、从而形成去屏蔽区域。P13:Hydrogen bonding shifts the resonance signal of a proton to lower field(higher frequency).Concertations and temperature all affect the hydrogen bonds in solution and also affects the chemical shifts of protons.The dilution of the solution reduces the hydrogen bonds between the molecule

15、s,leading to high shift.Low concentration(should be temperature)facilitates association,leading to lower field shift.P13：氢键使质子的共振信号向低场（较高的频率）移动。浓度和温度都会影响溶液中的氢键，因此也会影响质子的化学位移。溶液的稀释减少了分子之间的氢键，导致向高场位移。降低温度有助于缔合作用，导致向低场位移。P14:The other Factors of Influencing Chemical Shifts include steric effect and Van

16、 der Waals deshielding effect.P14：影响化学位移的其他因素包括空间效应和范德华去屏蔽作用。P16:Solvent effect also influence chemical shift.Here is the 1H NMR spectra of radically prepared PMMA measured a)in chloroform and b)in benzene.P16：溶剂效应也会影响化学位移。这是自由基制备的 PMMA 的1 H NMR 谱图，a）在氯仿中，b）在苯中。P17:For the summary,the factors of inf

17、luencing chemical shift include:1.Electronegativity deshielding Effect（电负性-去屏蔽效应）2.Anisotropy(due to magnetic fields generated by bonds)（化学键的各向异性）3.Conjugation Effect（共轭效应）4.Hydrogen Bonding（氢键作用）5.Steric Effect（空间效应）6.Solvent Effect（溶剂效应)P17：总结一下影响化学位移的因素包括：1.负电性-屏蔽（电负性-去屏蔽效应）2.各向异性（由于键产生的磁场）（化学键的排

18、列）3.共轭效应（共轭效应）4.氢键作用 5.立体效应（空间效应）6.溶剂效应 P18:Then lets look at the Typical Chemical Shifts of Organic Compounds.The chemical shifts of alkane protons are in the high field and are shifted to the low field by the influence of electronegativity and anisotropic effects.P18：然后让我们看一下有机化合物的典型化学位移。烷烃质子化学位移值

19、在高场区，并受电负性和各向异性的影响向低场移动。P19:As for alkene protons,the chemical shifts of protons in the terminal group range from 4.8 to 5 ppm,the middle groups are from 5.1-5.7 ppm.When conjugated with alkene and aromatics,chemical shifts are from 4 to 7 ppm.The chemical shifts of protons in Aromatic hydrocarbon a

20、re 6.58.0ppm,and Benzene protons are at 7.3 ppm When substituted with electron donating groups,chemical shifts are from 6.5-7.0 ppm.And When substituted with electron withdrawing groups,chemical shifts are from 7.2-8.0 ppm.P19：对于烯烃质子，端基质子的化学位移为 4.8 至 5 ppm，中间基团为 5.1-5.7 ppm。当与烯烃和芳烃共轭时，化学位移为 4-7 ppm。

21、芳香烃中质子的化学位移为 6.58.0ppm，苯质子化学位移为 7.3ppm 当被给电子基团取代时，取代芳烃质子化学位移为 6.5-7.0 ppm。当用吸电子基团取代时，取代芳烃质子化学位移为 7.2-8.0 ppm。P20:The chemical shifts of protons of carboxyl acids are at the lower field,from 10 to 13 ppm.Aldehyde protons are from 9 to 10 ppm.And for active protons of hydroxyl group and amines have a

22、wide range of chemical shifts.Fatty amines are from 0.4 to 3.5ppm Aromatic amine are from 2.9 to 4.8ppm And Amides are from 9 to 10.2 ppm P20：羧酸质子的化学位移在较低的范围，从 10 到 13 ppm。醛氢为 9至 10 ppm。对于羟基和胺的活泼氢，其化学位移范围很广。脂肪胺为 0.4 至 3.5ppm 芳香胺为 2.9 至 4.8ppm 酰胺为 9 至 10.2 ppm P21:The exchange rate of active protons

23、are as follows:OH NH SH,has a wide range.For active Hydrogens:Firstly,No spin coupling split with adjacent protons Secondly,When heavy water is used as a solvent,the absorption peak is no longer displayed Third,Generally,the association peaks of amides and carboxylic acids are broad peaks.Sometimes

24、they are hidden in the baseline.Its existence can be judged from the integral height.Fourth,The peak shape of alcohol and phenol is blunt,and the peak shape of amino and thiol is sharper.P21：活泼氢的交换率：OH NH SH，的变化范围大。对于活泼氢：（1）与相邻质子没有自旋偶合（2）当使用重水作为溶剂时，不再显示吸收峰（3）一般而言，酰胺与羧酸的缔合峰为宽峰。有时它们隐藏在基线中。它的存在可以从峰的整体积

25、分来判断。（4）醇和苯酚的峰形较钝，氨基和硫醇的峰形较尖锐。P22:We can use this table or this graph to remember the chemical shifts of protons for common organic molecules,very quickly.P22：我们可以使用此表或该图快速记住常见有机化合物的质子化学位移。P23:And We also can use the chemNMR tool to obtain chemical shift values.Draw your structure of interest with C

26、hemDraw then predict 13C and 1H NMR chemical shifts with the ChemNMR tools.In case of 13C NMR,over 95%of the shifts can be predicted with a mean deviation of 3.8 ppm.In case of 1H NMR,shifts of about 90%of all CHx-groups can be predicted with a mean deviation of 0.2-0.3 ppm.插入图 23 P23：我们也可以使用 chemNM

27、R 工具获得化学位移值。使用ChemDraw 绘制化合物结构，然后使用 ChemNMR 工具预测13C 和1H NMR 谱化学位移。可以预测超过 95的13 C NMR 化学位移，平均偏差为 3.8 ppm。可以预测所有 CHx 基团约 90的 1H NMR 化学位移，平均偏差为 0.2-0.3 ppm。插入图 23 P25:But the use of polar solvents may strongly increase these deviations.1H NMR shifts of hydrogen atoms bonded to hetero atoms are not pred

28、icted because they are affected by solvents,concentration,impurities and steric effects.And so for todays lesson,we have learned the factors of influencing frequencies and chemical shifts for organic compounds.Thank you for watching.P25：但是使用极性溶剂可能会大大增加这些偏差。结合杂原子的氢原子的1 H NMR 位移无法预测，因为它们受溶剂，浓度，杂质和空间效应的影响。因此，在今天的课程中，我们学习了影响有机化合物的频率和化学位移的因素。谢谢观看！