质评 51 CHF 53C4H5 54 CHy CH2C=N 55 C4H,, CH==CHC=O 56 CAHg 57C4H9,C2H5C=0 58 CH3-C+ H, C2H5 CHNH2, (CH3)NCH2 CH CHsNHCH2, C2H,s