Bond Strengths Recall that the nt bond of an alkene is weaker than its o bond. Bond Total Energy Class of Bond Approximate Energy C-C 347 kJ(83 kcal) alkane sigma bond 347 kJ (83 kcal) C=C 611 kJ(146 kcal) alkene pi bond 264 kJ (63 kcal) CC 837 kJ(200 kcal) second alkyne pi bond 226 kJ(54 kcal) The sum of the two at bonds in an alkyne are weaker than the sum of two alkene nt bonds. The triple bond is electron rich and acts as a nucleophile (just like a double bond). 2 o bonds t bond [o bond A-P R一C=C-R'+A一B Since addition reactions convert bonds into o bonds,these reactions are typically exothermic. Alkynes can add up to two molecules across the triple bond. Ch09 Alkynes (landscape) Page 9Ch09 Alkynes (landscape) Page 9 Bond Strengths Recall that the  bond of an alkene is weaker than its  bond. The sum of the two  bonds in an alkyne are weaker than the sum of two alkene  bonds. The triple bond is electron rich and acts as a nucleophile (just like a double bond). Since addition reactions convert  bonds into  bonds, these reactions are typically exothermic. Alkynes can add up to two molecules across the triple bond