Chapter s alkenes alkane alkene alkyne methane ethane ethene ethyne(acetylene) propane propene propyne C= C functional group(功能基) C-C Bond energy 88 152(kcal/mol) Bond length 1.54 1.34(A°Chapter 5 Alkenes alkane alkene alkyne methane ethane propane … ethene propene … ethyne(acetylene) propyne … C=C functional group (功能基） C-C C=C Bond energy 88 152 (kcal/mol) Bond length 1.54 1.34 (A°)