《有机化学》第九章核磁共振谱红外光谱和质谱（第三版）

OrganicChemistryXumiaoqing第九章核磁共振谱、红外光谱、紫外光谱和质谱OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing§9.1核磁共振谱9.1.1核磁共振谱的基本原理原子核存在自旋运动，可用自旋量子数I表征。NMR:I=1/2的核，如1H,13C,15N,19F,31P均匀不均匀有有1/23/2,5/2,…奇数或偶数奇数不均匀有1,2,3,…奇数偶数均匀无0偶数偶数电荷分布NMR信号I原子序数质量数OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing图9.1在外加磁场H0内,质子的两种自旋态(a)磁矩与Ho同时平行,能量较低.(b)磁矩与Ho反向平行,能量较高.OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing这两种自旋态的能量差△E与外加磁场的强度成正比:其中γ为质子的特征常数,h0为普朗克常数,H0为外加磁场的强度　hr当E射=hν射=⊿E时⊿E=——H0rH02π（r为核常数）ν射=——2πhr当E射=hν射=⊿E时⊿E=——H0rH02π（r为核常数）ν射=——2πOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing外加磁场强度图9.2在外加磁场Ho内,质子的两种自旋态处于不同的能级,其能量差△E与外加磁场强度成正比△E△E/OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing射频输入振荡器射频输出信号放大器NMR谱Ho样品管射频输入线圈射频输出线圈图9.3核磁共振仪示意图OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing磁场强度9.1.2化学位移:原子核(如质子)由于化学环境所引起的核磁共振信号位置的变化称为化学位移.低磁场高磁场图9.4质子在不同环境下的核磁共振信号(a)独立质子的信号在Ho处出现,(b)有机化合物中的质子在高磁场(H0’＞Ho)OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing图9.5碳-氢键上的电子在外加磁场中产生感生磁场,其方向与此同时Ho相反9.1.2.1屏蔽效应(shieldingeffect)为什么有机化合物中的质子在高磁场(H0’＞Ho)?是由于分子中的电子对质子有屏蔽作用.OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.1.2.2化学位移(chemicalshift)图9.6氯仿(CHCl3)的1HNMR谱图(60MHZ)OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing化学位移(δ)=×106信号位置－TMS峰的位置核磁共振仪所用频率例如:氯仿中质子的化学位移为:δ=×106=7.28437HZ-0HZ60×106HZOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.1.2.3结构对化学位移的影响卤原子的电负性减小甲基质子经受的屏蔽效应率应增加CH3FCH3ClCH3BrCH3Iδ4.33.12.72.2与甲基相连的原子电负性减小甲基质子经受的屏蔽效应增加CH3FCH3OCH3(CH3)3NCH3CH3δ4.33.22.20.9OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingCHCl3CH2CCl2CH3Clδ7.35.33.1δ7.35.30.9为什么？OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing(a)(b)图9.7π电子所产生的感生磁场OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingδ=-1.9δ=8.2OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.1.2.4等价质子和不等价质子δ=5.3δ=5.5OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.1.2.5积分曲线OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.1.3自旋裂分分子中位置相近的质子之间自旋的相互影响称为自旋-自旋偶合(spin-spincoupling)自旋偶合使核磁共振信号分裂为多重峰,称为自旋裂分(spin-spinsplitting)OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingHaHbHbHa1:3:3:11:1OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing与某一质子邻近的质子数为n时,核磁共振信号裂分为n+1重峰,其强度如下:与某一质子偶合的等价质子数目峰裂数多重峰中各峰的强度化1双峰(d.)1:12三重峰(t.)1:2:13四重峰(q.)1:3:3:14五重峰1:4:6:4:15六重峰1:5:10:10:5:16七重峰1:6:15:20:15:6:1裂分的式样一般可依下列情况计算:(n+1)规则,自旋偶合的邻近H原子都相同时才适用(n+1)规则.如:CH3CHCl2OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing(2)如果自旋偶合的邻近H原子不同时,裂分的数目为(n+1)(n’+1).如:Cl2CH-CH2CHBr2.-CH2-应裂分成(1+1)(1+1)=4重峰Cl2CH-应裂分成(2+1)=3重峰-CHBr2应裂分成(2+1)=3重峰OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing§9.2红外光谱9.2.1红外光谱的一般特征OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.2.2红外光谱的基本原理9.2.2.1双原子分子的振动:OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing9.2.2.2质量和力常数的影响OrganicChemistryXumiaoqing9.2.2.3振动的偶合(伸缩振动)非对称伸缩2930cm-1对称伸缩2850cm-1OrganicChemistryXumiaoqing9.2.2.4弯曲振动+++－面内弯曲面外弯曲剪式振动平面摇摆非平面摇摆扭曲振动＋号表示原子向纸面前方运动，－号表示向纸面后方运动OrganicChemistryXumiaoqingInfraredSpectroscopy横坐标---波数（cm-1,下方）,波长(mm,上方）纵坐标---吸光强度（A）或透过率（T，%）谱区---4000–600cm-1分两个区---官能团区（4000–1400cm-1)---伸缩振动---指纹区（1400–600cm-1)---弯曲振动红外光谱图OrganicChemistryXumiaoqingInfraredSpectroscopyHook’sLaw(forstretchingvibration)1、振动频率与成键原子折合质量倒数的平方根成正比，即原子质量愈轻，振动频率愈高；2、振动频率与键的力常数的平方根成反比，即键能愈大，键长愈短，键的力常数愈大，振动频率愈高。OrganicChemistryXumiaoqingC=CC=CC-C-C-H=C-H=C-H2100-22601600-1670800-12002850-29603010-3100~3300C=OC-O-O-H1660-17801000-13003580-3670C=NC=NC-N-N-H2210-22601630-16901250-13603310-3400(s,ordpeaks)StrongerbondsandlighteratomsgiverisetohigherwavenumbersOrganicChemistryXumiaoqing不同类型键的伸缩振动频率OrganicChemistryXumiaoqing影响红外吸收频率的因素——电子效应与共振结构、氢键、空间效应ResonanceEffecte.g.1.C=Oin2-pentanone1720cm-1butin2-cyclohexenone1680cm-1OrganicChemistryXumiaoqing氢键对吸收峰频率影响举例OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing§9.3质谱9.3.1质谱的基本原理OrganicChemistryXumiaoqingMassSpectrometryMmoleculeeM+emolecularionaradicalcationelectronFragments分子离子的产生OrganicChemistryXumiaoqing仪器工作原理图OrganicChemistryXumiaoqing质谱图样式OrganicChemistryXumiaoqing1、从同位素相对峰强度计算Example:Themassspectrumofanunknowncompoundhasamolecularionwitharelativeintensityof43.27%,andanM+1peakwitharelativeintensityof3.81%.Howmanycarbonatomsarethereinthecompound?分子量、分子式的确定OrganicChemistryXumiaoqingSolution:Therearetwonaturallyisotopesofcarbon:98.89%12Cand1.11%13C同位数丰度表见后分子量、分子式的确定OrganicChemistryXumiaoqing同位素峰度表ElementNaturalabundanceHydrogen1H99.99%2H0.01%Carbon12C98.89%13C1.11%Chlorine35Cl75.77%37Cl24.23%bromine79Br50.69%81Br49.31%OrganicChemistryXumiaoqing同位素离子峰可以帮助确定分子组成——含Cl,Br原子的分子——强度比符合二项式（a+b)n的展开式其中，a–常见元素的丰度b–同位素的丰度n-该元素的个数如：CHCl3:(3+1)3=27+27+9+1So,M:(M+2):(M+4):(M+6)=27:27:9:1OrganicChemistryXumiaoqingOrganicChemistryXumiaoqing2、从高分辨质谱分子量计算High-ResolutionMassSpectrometry(HRMS)candeterminetheexactmolecularmassofafragmentwithaprecisionof0.0001amu.分子量、分子式的确定OrganicChemistryXumiaoqingExampleSomecompoundswithanominalmolecularmassof122amuandtheirexactmolecularmassesC9H14C7H10N2C8H10O122.1096122.0845122.0732C7H6O2C4H10O4C4H10S2122.0368122.0579122.0225分子量、分子式的确定OrganicChemistryXumiaoqing2.分子离子峰的断裂规律（1）游离基中心引发的裂解（2）电荷中心引发的裂解推导有机物分子结构OrganicChemistryXumiaoqing(1).游离基中心引发的裂解这类断裂反应也称为a-裂解，可用通式表示：（邢其毅教材中将它称为β-裂解）注意：质谱中单电子的转移用鱼钩表示，双电子的转移用箭头表示OrganicChemistryXumiaoqing醇、醚、胺和卤代烃等常发生上述裂解OrganicChemistryXumiaoqing杂原子对正电荷的致稳作用，随杂原子的电负性降低而增强，即：N>S>OOrganicChemistryXumiaoqing含烯丙基、苄基的烃类也发生α-裂解OrganicChemistryXumiaoqing含有羰基的化合物，如醛、酮、酯等也易发生α-裂解：OrganicChemistryXumiaoqing(2).电荷中心引发的裂解又称为诱导裂解，用i表示奇电子离子OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqing紫外光谱——给出共轭双键的信息——givesusinformationaboutcompoundswithconjugateddoublebondUltravioletandvisiblelighthasjusttherightenergytocauseanelectronictransition——thepromotionofanelectronfromoneorbitaltoanotherofhigherenergyOrganicChemistryXumiaoqingUltravioletandVisibleSpectroscopyTheelectronicenergystates:OrganicChemistryXumiaoqingTheBeer-Lambertlaw:A=clε吸光度A=logI0/II0：进入样品的光强度I：透过样品的光强度摩尔浓度c样品池长度l（incm)摩尔吸光系数εOrganicChemistryXumiaoqing影响摩尔吸光系数ε的因素：跃迁类型由于n轨道的电子与π电子集中在不同的空间区域，因此尽管nπ*的跃迁需要的能量较低，其跃迁的几率是比较小的。表现在摩尔吸光系数ε值较小OrganicChemistryXumiaoqingOrganicChemistryXumiaoqingEffectofconjugationonλmax——conjugationraisestheenergyoftheHOMOandlowerstheenergyoftheLUMOOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingOrganicChemistryXumiaoqingAchromophore（生色团）isthatpartofamoleculethatisresponsibleforaUVorvisibleabsorptionspectrum.Anauxochrome（助色团）isasubstituentthat,whenattachedtoachromophore,alterstheλmaxandtheintensityoftheabsorption,usuallyincreasingbothofthem.(OHandNH2areauxochromes)OrganicChemistryXumiaoqingAshifttoalongerwavelengthiscalledaredshiftandashifttoshorterwavelengthiscalledablueshiftOrganicChemistryXumiaoqing作业P224页：1.(1)(4)(602.(2)(4)