Bond dissociation energy values carbon -nitrogen

C—H bond energy and of a likewise higher value of the heat of dissociation of nitrogen. The values between brackets in the second and fourth columns are based on the low value for the heat of vaporization of carbon but on an intermediate value for the dissociation energy of nitrogen of 225.1 kcal. 

Despite their high dissociation energy of 133 kcal/mol, sp C—H bonds are prone to C—H bond activation. Indeed, the simplest alkyne, acetylene, has a rather small pR, value of25—26, which makes it a weak acid in organ-ometaUic chemistry, and can be deprotonated by a strong base such as a nitrogen- or carbon-based anion. Therefore, the reaction between a metal alkyl complex and a primary alkyne is usually thermodynamically favorable and resembles a classical acid—base metathesis reaction. 

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