常见有机化合物的裂解方式和规律

一、烃二、芳烃三、醇四、醛、酮五、酸和酯类第四节常见有机化合物的裂解方式和规律1.直链烷烃1615m/zmethaneM=16一、烃的质谱图m/z15294357859911314271m/z15294357859911314271正癸烷分子离子：C1(100%)，C10(6%)，C16(小)，C45(0)有m/z：29，43，57，71，……CnH2n+1系列峰(σ—断裂)有m/z：27，41，55，69，……CnH2n-1系列峰C2H5+（m/z=29）→C2H3+（m/z=27）+H22.支链烷烃20406080100120140160180200103050709011013015017019021022023010080901006050302040700%OFBASEPEAKC3m/z=43C4m/z=57C5m/z=71C8m/z=85C6m/z=99C7113C9C10C12C16M15M5-MethylpentadecaneCH3(CH2)3CH(CH2)9CH3CH38516914157•裂解容易发生在分支部位，优先失去最大的烷基，形成稳定的仲碳或叔碳阳离子•（正离子稳定性顺序R3C+R2C+HC+H2C+H3）84(M)0204060801001030507090110695541271008090100605030204070%OFBASEPEAKCHCH3CCH3CH2CH3CHCH3CCH3CHCH3CCH3CH2CH3CH2CH3m/z=69m/z=553.烯烃1)分子离子峰较稳定；2)41+14n峰3)β-裂解,41强4)CnH2n,42，重排离子峰（麦氏重排）5)环状稀烃能发生RDA裂解β-裂解54M412767108090100605030204070%OFBASEPEAK082392040608010010305070900134(M)1008090100605030204070%OFBASEPEAK0204060801001030507090110917792513912013014065CH2CH2CH2CH3二、芳烃的质谱图特点•M+较强•C6H5-R,β-裂解,m/z91（C7H7+基峰）•C6H5-R,α-裂解，m/z77（C6H5+）•r-氢的C6H5-R，Melafferty重排,C7H8+（m/z92）β裂解91α裂解77Melafferty重排,C7H8+（m/z92）CH2CH2CH2CH3CH2m/z=91m/z=91m/z=65m/z=39m/z=134HCCHHCCHCH2CH2CH3H2CCH2CHHCH3CH2HHm/z=92CH2HCCH3CH2CH2CH2CH3m/z=77m/z=134m/z=51HCCHC4H9CH2CH2CH2CH3CH2m/z=91m/z=91m/z=65m/z=39m/z=134HCCHHCCHCH2CH2CH3H2CCH2CHHCH3CH2HHm/z=92CH2HCCH3CH2CH2CH2CH3m/z=77m/z=134m/z=51HCCHC4H9三.醇类•①分子离子峰很小，随C链↑而↓，甚至消失（C5时），（易脱水）。•②易发生α裂解，31+14n•③脱水重排，M-18峰•④直链伯醇含羟基碎片（31，45，59），烷基离子（29，43，57）及链烯离子（27，41，55）三种系统的离子，质谱峰多R2CR1R3OH-R3R2CR1OHm/z:31,59,73,RHCHCH2OHRHCCH2OHH-H2ORHCCH2RHCCH2(CH2)n(CH2)n(CH2)n(CH2)norα裂解M-18峰RHCHCH2CH2CH2O+HH2CCH2-H2OM-(Alkene+H2O)M-46H2CCHR-RHCHHCCH2CH2O+HCH3H2CHC-H2O-CH3H2CCHRM-60HCCH2H2CCHHH2CRH2CCH2-CH2CHH2CRM-76脱水脱烯1008090100605030204070%OFBASEPEAKCH2OHM-(H2OandCH2CH2)M-(H2OandCH3)M-H2OM-11-PenTanolMW88CH3(CH2)3CH2OH314060801001201401030507090110130150020Cα－Cβ断裂1008090100605030204070%OFBASEPEAK57M-CH2CH2M-H2OMMW1424060801001201401030507090110130150020M-1M-44M-43CH3(CH2)7CHO44四、醛、酮的质谱图•M+明显•α-裂解，M-1峰•γ-H麦氏重排，44•β裂解CORH＋.CR＋OCH＋OR＋55M0204060801001030507090422769108090100605030204070%OFBASEPEAK098O1008090100605030204070020406080100120140%OFBASEPEAK1030507090110130150Figure2.14.MethylOcatanoateCOCH3OCH2CH2OCH3O121[M-31]MM+1M+2MethyloctanoateCH3(CH2)6COOCH3158(M)159(M+1)160(M+2)160875974COHOCH3H2C五、酸和酯类OCh3(CH2)4CO(small)99CH3(CH2)471CH3(CH)357CH3(CH2)243CH3CH229CH3CH2CH2CH2CH2COH45CO2H59(small)CH2CO2H73(CH2)2CO2H87(CH2)3CO2H•一元饱和羧酸及酯的分子离子峰弱，芳酸及酯强•α裂解，M-1峰（羧酸）•γ-H麦氏重排α裂解六、胺和酰胺2H2HH2H2R+C+.R+C.NN1、脂肪胺的分子离子峰很弱或者消失，芳香胺及酰胺的分子离子峰较强2、发生β-裂解：m/e30