Abstract: Studies on Methane-Chemical Ionization Mass Spectra of Double-Bond Positional Isomers of Dodecenyl AcetatesYuan Gu(Department of Chemistry,Peking University,Beijing 100871,China)Received Abstract:The chemical ionization mass spectra of △2~△11-dodecenyl acetates have been investigated using methane as reactant gas.The ten isomers undergo extensive fragmentation to produce the spectra consisting of series of CnH2n-1,CnH2n-2,and CnH2n-3,ions.The CI spectra of these isomers are very similar and give similar fragmentation patterns,which are dominated by the double bond migration and radical-site rearrangements along the carbon chain with the aid of consecutive rearrangements of hydrogen atoms.Keywords:dodecenyl acetates,double-bond positional isomers,methane-chemical ionization mass spectra