sentence: the n ≡ n triple bond of is much stronger ( energy of formation of 229 kcal / mole ) than either an equivalent one-and-a-half n = n double bond ( 100 kcal/mole , i.e. 150 kcal/mole total ) or an equivalent three n-n single bond ( 38.4 kcal/mole , i.e. 115 kcal/mole total ) .