Why are addition reactions of alkenes exothermic?

1 Answer
Aug 21, 2016

Well, you are making "carbon-carbon"carbon-carbon or "carbon-heteroatom"carbon-heteroatom bonds, and given this it is inevitably exothermic.

Explanation:

It is generally observed that bond formation is exothermic, and bond-breaking is endothermic. Olefin reactions generally involve the formation of 2xxC-X2×CX bonds of some sort. Of course, we must break an X-XXX bond of some sort, but formation of 2xxC-X2×CX bonds is energetically downhill.