核磁共振氢谱2

自旋偶合与裂分Spin-SpinCouplingandSplitting刘和文自旋偶合现象e1n1n2e2CH2CH3低分辨高分辨J自旋-自旋偶合自旋核与自旋核之间的相互作用（干扰）偶合的结果造成谱线增多，称之裂分偶合的程度用偶合常数（J）表示，单位:Hz自旋偶合•不同的n和B，引起主峰间距变化，但Ｊ不变。不是化学位移现象。•它不属于偶极距间的直接相互作用，对于液体来讲，分子翻滚运动很快，偶极距间的作用可近似为零。•与化学键的键型、键角和核自旋有关。由自旋核在B0中产生的局部磁场分析例如Cl2CH-CH2ClBoCHCH2自旋-自旋偶合机理CH3CH2-BoCH3CH2根据Pauli原理和Hund规则，每个成键轨道最多只能容纳2个电子且自旋方向相反；同一成键原子的电子自旋方向平行；电子自旋方向与核自旋方向相同，核自旋能级升高，电子自旋方向与核自旋方向相反，核自旋能级降低。由自旋核在B0中能级的改变分析（接触机理）HaCHbCEEE2E1B0对于Hb核，考虑Ha核对其影响时：ΔE1ΔEΔE2ΔE1=h(νb–J/2)=hν1ΔE2=h(νb+J/2)=hν2ΔE2–ΔE1=h(ν2–ν1)=hΔνΔν=J(Hz)某组环境相同的氢核，与n个环境相同的氢核（或I=1/2的核）偶合，则被裂分为(n+1)条峰。（n+1）规律WedApr1210:16:352000:(untitled)W1:1HAxis=ppmScale=41.38Hz/cm6.5006.0005.5005.0004.5004.0003.5003.0002.5002.0001.5001.0000.500例如乙醇(普通)某组环境相同的氢核，分别与n个和m个环境不同的氢核（或I=1/2的核）偶合,则被裂分为(n+1)(m+1)条峰（实际谱图可能出现谱峰部分重叠，小于计算值）。例如高纯乙醇：J(OH-CH)≠JCH2-CH3WedApr1210:21:202000:(untitled)W1:1HAxis=ppmScale=41.38Hz/cm6.5006.0005.5005.0004.5004.0003.5003.0002.5002.0001.5001.0000.500CH2共振吸收的扩展图WedApr1210:24:442000:(untitled)W1:1HAxis=ppmScale=2.59Hz/cm3.7003.6603.6203.5803.5403.5003.4603.4203.3803.34011112113311464115101051......n=023451singlet,sdoublet,dtriplet,tquintetquartet,qsixtet裂分峰的相对强度比近似为（a+b）n展开式的系数比(N+1)规律的近似处理运用范围：△ν/J6向心规则：相互偶合的峰，内侧高，外侧低。化学位移值(δppm)：中心与重心之间。偶合常数值(JHz)：相邻两裂分峰之间的距离WedApr1210:40:132000:(untitled)W1:1HAxis=ppmScale=18.89Hz/cm3.8003.6003.4003.2003.0002.8002.6002.4002.2002.0001.8001.6001.4001.2001.000例：分子式C4H8Br2，1HNMR谱(a,b)如下，推导其结构21XHC例分子式C8H12O4，1HNMR谱如下，推导其结构WedApr1211:14:462000:(untitled)W1:1HAxis=ppmScale=39.69Hz/cm6.5006.0005.5005.0004.5004.0003.5003.0002.5002.0001.5001.000核的等价性化学等价（Chemicalequivalence）化学等价与否，是决定NMR谱图复杂程度的重要因素。在分子中，若通过快速旋转或某种对称操作，一些核可以互换（Interchange）,则这些核称之化学等价核。σ键的快速旋转导致的化学等价：CH3-CH2-O-，X-CH2CH2-YXYXXNXXHaHbabcdab对称性导致的化学等价：通过对称轴旋转而互换的质子称之等位（HomotopicorIdentical）质子，无论是非手性还是手性环境。ClHcClHdHaHbClHdClHcHaHb180o分子中无对称轴，但与其他对称因素相关的质子称之对映异(Enantiotopic)质子。例如HBrClC6H5DHHBrClC6H5HaHbHBrClC6H5HD(a)(b)分子中不能通过对称操作进行互换的质子称之非对映异位(Diastereotopic)，无论是在有手性中心的分子还是无手性中心的分子中。例如H3COOCCH2HaHbCH3CH3ab磁等价分子中某组核化学环境相同，对组外任一核的偶合相等，只表现出一种偶合常数，则这组核称为磁等价核。磁全同的核既化学等价又磁等价的核。例如：化学等价，磁等价(σ键的快速旋转导致)CH3CH2OHCH3CH2OCH2CH3化学等价，磁不等价HaHbaaˊ,bbˊaaˊ,bbˊXHbF1baabcHaF2Naabbcˊˊˊˊ化学不等价，磁不等价:abc,aaˊbbˊc，aaˊbbˊXHbHcbaabcHaFaabbXYˊˊˊˊH3COOCCH2HaHbCH3CH3R1R3R2HaHbXXYHaHbHcOOCH3HbHcHfHdHeOOHbHaHc偶合常数与分子结构的关系质子与质子(1H，1H)之间的偶合。其他核(19F,31P,13C,2H,14N)与质子之间的偶合。质子与质子(1H，1H)之间的偶合通过两个键之间的偶合---同碳质子间的偶合通过三个键之间的偶合---邻碳质子间的偶合大于三键之间的偶合---远程偶合同碳质子间的偶合（2J或J同）Ha—C—Hb,用2J或J同表示。变化范围大。例如OHbHaCOOHOOHaHb21.5HaHbX3.19.110~16HzHb*CCHaHbzHa影响2J的因素邻位π键的影响CH4CH3PhCH3COCH3CH3CNCH2(CN)2-12.4~-14.3-14.9-16.9-20.4键角（）的影响：角增大，2J减小HaHbX3.19.1CCHaHb~2Hz1016~5Hz~12HzHbHa3[phone]ooo取代基电负性的影响：取代基电负性增大，2J值增大。SHaHbNHaHbOHaHb1.3897PhPhPh2J应用实例例1解释4-氧杂环戊酮衍生物的1HNMR谱AA计算机模拟的1HNMR谱SunApr0221:15:472000:(untitled)W1:1HAxis=ppmScale=28.40Hz/cm5.0004.6004.2003.8003.4003.0002.6002.2001.8001.4001.000OHdHeCH3HbHcHfO1.202.503.734.494.073.84化合物B计算机模拟化合物B的1HNMR谱ThuApr1319:35:122000:(untitled)W1:1HAxis=ppmScale=33.68Hz/cm6.0005.5005.0004.5004.0003.5003.0002.5002.0001.5001.000OHdHeHcHbCH3HfO2.572.151.404.043.834.35Jbf=9HzJcf=5.5HzJbc=18Hz邻碳质子间的偶合Ha—C—C—Hb,用3J或J邻表示饱和型化合物3J与两面夹角φ的关系Karplus方程:3J=J0cos2φ0.28(0o≤φ≤90o)3J=J180cos2φ0.28(90o≤φ≤180o)(J08~9Hz,J18011~12Hz)例如乙醇HbHbHbOHHaHaφ=60oJab=2~4Hz，φ=90oJab=~0Hzφ=120oJab=~3Hz，φ=180oJab=11~12Hz快速旋转的σ键，3J6~8Hz(为60o，180o的平均值)环己烷:2Jae=2Jaˊeˊ~12Hz3Jaaˊ（180o）8~12Hz，~10Hz3Jaeˊ（60o）或3Jeaˊ2~6Hz，3Jeeˊ2~5Hz~4HzHaHeHeHaJeaJeeJaaJaeˊˊˊˊˊˊ饱和型3J的应用用于赤式和苏式构型的确定大赤式HaHb大小小大HaHb大小小大HaHb大小小(I)(II)(III)赤式构型的稳定构像以(I)为主，3Jab8~12Hz。若有分子内氢键存在时，以形成内氢键的稳定构像为主。赤式的Newman投影苏式大HaHb大小小大HaHb大小小大HaHb大小小(I)(II)(III)苏式构型的稳定构像以(III)为主，3Jab2~4Hz。若有分子内氢键存在时，以形成内氢键的稳定构像为主。苏式的Newman投影麻黄碱（赤式构型）的稳定构像OHHaHbCH3NHCH3PhHaHbHOCH3NHCH3Ph(II)(III)OHHaPhCH3NHCH3HbHaPhHOCH3NHCH3Hb(I)(II)伪麻黄（苏式构型）的稳定构像3Jef=4Hz,分子内氢键，赤式构像，麻黄碱。3Jef=10Hz,分子内氢键，苏式构像，伪麻黄碱ThuMar2217:27:152001:(untitled)W1:1HAxis=ppmScale=21.67Hz/cm4.8004.6004.4004.2004.0003.8003.6003.4003.2003.0002.8002.6002.4002.2002.0001.8001.6001.4001.2001.0000.8000.6000.400NHHOecfabd用于确定六元环中CH3为a或e键（实测17Hz）H2aH4eH2e18HzH3H3COHOHH3CH34HH4H3H2aH4aH2e24HzH3OHCHOOHCHO10Hz10Hz10Hz10Hz4Hz4Hz4Hz4Hz4Hz4Hz4HzOHCH3CHOOH1234用于判断烯烃取代基的位置烯烃HcHaHbXJab~2HzJac8~12HzJbc12~18HzJcisJtransJcis1~2Hz2~4Hz5~7Hz9~11Hz例C5H8O2的1HNMR谱如下,推导其结构FriApr1418:29:582000:(untitled)W1:1HAxis=ppmScale=52.82Hz/cm8.0007.5007.0006.5006.0005.5005.0004.5004.0003.5003.0002.5002.0001.5001.0000.500FriApr1418:32:042000:(untitled)W1:1HAxis=ppmScale=20.99Hz/cm7.4007.2007.0006.8006.6006.4006.2006.0005.8005.6005.4005.2005.0004.8004.6004.400δppm:1.16(t3H),2.36(q2H),4.47(dd1H),4.77(dd1H),7.24(dd1H)NONHS3.53.43.41.82.64.7XXJo6~8HzJ2,3=J5,63J2,53J2,53J2,5Jm1~2Hz~5Hz1.5Hz2.1Hz2.8HzJp0~1HzJ3,4=J4,5~8Hz芳环及杂芳环上芳氢的偶合例C11H12O5的1HNMR谱如下，推导其结构FriApr1421:15:122000:(untitled)W1:1HAxis=ppmScale=57.83Hz/cm11.00010.0009.0008.0007.0006.0005.0004.0003.000C11H12O5的1HNMR谱的部分展开图FriApr1421:17:392000:(untitled)W1:1HAxis=ppmScale=8.12Hz/cm7.6007.5007.4007.3007.2007.1007.0006.9006.8006.7006.6006.5006.400