Elements or Degrees of Unsaturation:n-Bond or Ring CH,=CH-CH,CH CH一CH=CH一CH3 1-butene 2-butene CH3 CH-CH, CH2 CH,-C-CH, CH,-CH2 CH,一CH一CH3 isobutylene cyclobutane methylcyclopropane Elements or Degrees of Unsaturation: p-Bond or Ring