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1、P1:Hello everyone,welcome to Organic Spectroscopic Analysis.In the last lecture,I have introduced you 13C NMR spectroscopy.This lecture,we are going to learn more about it.P1：大家好，歡迎來(lái)到有機(jī)波譜分析課程。在上一講中，我向大家介紹了13C NMR 光譜，這一節(jié)課我們將了解更多13C NMR。P2:In 13C NMR,chemical shifts are in the range of 0-230 ppm,much

2、wider window than 1H NMR.The 13C NMR signal for TMS is again the standard.Similar to 1H NMR,there are same kinds of factors influence chemical shifts.P2：在13C NMR 中，化學(xué)位移在 0-230 ppm 的范圍內(nèi)，比 1H NMR 的范圍寬得多。TMS 也是13 C NMR 的內(nèi)標(biāo)。與1H NMR 具有相似的影響化學(xué)位移的因素。P3:13 C NMR spectrum gives you:1.Number of Different Carb

3、on atoms 不同碳原子的數(shù)目 2.Chemical Type of Carbons 碳的化學(xué)類(lèi)型 13 C NMR has Wide chemical shift range.The common chemical shift range of 1H NMR is 0-10ppm,and the common range of 13C NMR is 0-120,which is about 20 times of 1H NMR.This greatly eliminates the overlapping of carbon atoms in different chemical env

4、ironments and greatly improves the resolution.P3：13 C NMR 光譜給出：1.不同碳原子數(shù)目 2.碳的化學(xué)類(lèi)型 13 C NMR 具有寬的化學(xué)位移范圍。1H NMR 的常見(jiàn)化學(xué)位移范圍為0-10，而13C NMR 的常見(jiàn)范圍為0-120，約為1H NMR 的 20 倍。這極大地消除了不同化學(xué)環(huán)境中碳原子峰的重疊，并大大提高了分辨率。(2)13 C NMR has large coupling constant Due to the low natural abundance of 13C,and the probability of the

5、carbon atom directly connected to C is very small,so 13C-13C coupling is generally not considered in Carbon NMR spectrum.Carbon atoms are often connected to hydrogen atoms,and they can be coupled to each other.13C-1H coupling constant value is very large,generally in 125-250 Hz.This coupling does no

6、t affect the 1H NMR spectrum,but it is dominant in the carbon spectrum.（2）由于13C 天然豐度低，與它直接相連的碳原子也是 13C 的幾率很小，故在碳譜中一般不考慮 13C-13C 偶合，而碳原子常與氫原子連接，它們可以相互偶合，這種 13C-1H 偶合常數(shù)的數(shù)值很大，一般在 125-250 Hz。這種偶合并不影響 1H NMR 譜，但在碳譜中是主要的。But usually,13C NMR is not quantitative.Because the peak intensity is not proportiona

7、l to the number of carbon atoms Only when the system is in equilibrium,that is,it forms to the Boltzmann distribution,and the intensity of the spectral peak is proportional to the number of resonance nuclei of the peak.Due to the long relaxation time of the 13C nucleus,the resonance peak is usually

8、observed in a non-equilibrium state,and the relaxation time of carbon atoms on different groups is different.So the intensity of the 13C NMR spectrum peak is often not the same as the carbon nucleus that produced the peak.通常，13C NMR 不定量，因?yàn)樽V峰強(qiáng)度不與碳原子數(shù)成正比。體系只有處在平衡狀態(tài)，即符合波爾茲曼分布時(shí)，譜峰強(qiáng)度才與該峰共振核數(shù)目成正比。由于13C 核

9、T1 較長(zhǎng)，共振峰通常都是在非平衡狀態(tài)下觀測(cè)的，加上不同基團(tuán)上的碳原子弛豫時(shí)間不同，因此13C NMR 的譜峰強(qiáng)度常常不與產(chǎn)生該峰的碳核數(shù)目成正比。P4:Common decoupling methods for 13C NMR include:Proton Broad Band Decoupling,Off-Resonance Decoupling,DEPT(Distortionless Enhancement of Polarisation Transfer,Selective proton decoupling spectrum(SPD),and Gated Decoupling and

10、 Inverted Gated Decoupling.P4：用于13 C NMR 的常見(jiàn)去偶方法包括：質(zhì)子寬帶去偶，失諧去偶，DEPT（極化轉(zhuǎn)移無(wú)畸變?cè)鰪?qiáng)技術(shù)），選擇性質(zhì)子去偶譜（SPD），門(mén)控去偶和反相門(mén)控去偶。P5:This is the proton-decoupled carbon-13C NMR spectrum of 2-butanol.Each C atom gives one sharp peak.P5：這是2-丁醇的質(zhì)子去偶碳13C NMR譜。每個(gè)C原子給出一個(gè)尖峰。P6:This is the off-resonance decoupling spectrum of 2-b

11、utanol for 1H-coupled carbon.The peak number follows the N+1 rule.P6：這是1H偶合碳的2-丁醇的偏共振去偶譜。峰值數(shù)遵循N+1規(guī)則。P7:The factors of influencing chemical shifts in 13C NMR are similar to 1H NMR，Electronegativity deshielding,Heavy atom effect,Electron deficiency effect,Conjugation Effect,Hydrogen Bonding,Steric Eff

12、ect and Solvent Effect P7：13C NMR 中影響化學(xué)位移的因素類(lèi)似于1H NMR，電負(fù)性-去屏蔽，重原子效應(yīng)，電子缺乏效應(yīng)，共軛效應(yīng)，氫鍵，立體效應(yīng)和溶劑效應(yīng).P8:Different hybridization of carbon atoms has different chemical shift range.The chemical shift sp3 Hybrid CH3 is 0 60ppm And sp HybridCCH is 60 90ppm sp2 Hybrid CHCH2 is 100 200ppm sp2 Hybrid C=O is 150 22

13、0ppm Electronegativity induction effect makes C,-C shift to downfield,but C to upfield because of steric effect.C-F C-Cl C-Br C-I P8：不同雜化的碳原子具有不同的化學(xué)位移范圍?；瘜W(xué)位移 sp3 雜化 CH3 為 060ppm sp 雜化-CCH 為 6090ppm sp2 雜化-CH CH2 為 100200ppm sp2 雜化 C=O 為 150220ppm 電負(fù)性作用使C,-C 移至低場(chǎng)，而C 由于空間效應(yīng)向高場(chǎng)移動(dòng)。C-F C-Cl C-Br C-I P9:H

14、ere is the table showing electronegativity effect on chemical shifts.P9：下表顯示了電負(fù)性對(duì)化學(xué)位移的影響。P10:Heavy atom effect Which is after the substitution of heavy halogen atom iodine-I,the chemical shift value of C is reduced,because there are a large number of electrons outside the I atom,which has a strong s

15、hielding effect on the C connected to it.P10：重原子效應(yīng) 被重鹵素原子碘 I 取代后，C 的化學(xué)位移值降低，因?yàn)樵?I 原子外部存在大量電子，這對(duì)與其相連的 C 具有很強(qiáng)的屏蔽作用。4.Conjugation effect The effect of uneven distribution of electrons due to conjugation,which shifts the value of C toward to up or down field.In the ortho position of C=O,an unsaturated b

16、ond or hetero atom is introduced to form a conjugated system.The density of the electron cloud on C=O carbon increases,and the shielding effect moves to a upfield。4.共軛效應(yīng) 電子因共軛而分布不均勻的影響，這會(huì)使 C 的值向高場(chǎng)或低場(chǎng)移動(dòng)。在 C O 的鄰位，引入不飽和鍵或雜原子以形成共軛體系。C=O碳上電子云的密度增加，產(chǎn)生屏蔽效應(yīng)移至高場(chǎng)。P11:This is the table showing electronegativity effect on chemical shifts.P11：下表顯示了電負(fù)性對(duì)化學(xué)位移的影響。P12:5.Steric effect:C separated by several bonds may have a strong influence due to the steric structure.Van der Waals is pushed away from the outer C