2-Methylpentane 100 43 80 M-43 CH3 CH3一CH-CH2一CH2-CH 60 2-methylpentane 40 M-45 M-29 71 20 57 M+ 86 0 10 20 30 40 50 60 70 80 90100110120130140150160 m/z 2-Methylpentane