# Why do acetylene and chlorine react to yield carbon and HCl, but acetylene and bromine react less intensely?

In the famous "underwater fireworks" reaction we get

$$\ce{C2H2 + Cl2 -> 2C + 2HCl}$$

On the other hand, when we react acetylene with bromine, we get

$$\ce{CH#CH + Br2 -> CHBr=CHBr}$$ $$\ce{CHBr#CHBr + Br2 -> CHBr2-CHBr2}$$

Why don't we get carbon and HBr? Or do we get it?

## 1 Answer

Bromine is not as strong of an oxidizing agent as chlorine. In essence the reaction of acetylene with chlorine is the same as burning, just with elemental halogen instead of elemental oxygen.

The higher electronegativity of chlorine explains why it is a good oxidant as compared to bromine.

Other notes:

• Describing something as 'radically' (this phrasing removed from original question edit) when you mean 'intensely' will cause much confusion around here (Stack) since 'radically' refers to reactions involving single electron mechanisms.