* Dibromomethane is already saturated: Dibromomethane has all its carbons bonded to four other atoms, meaning it's already fully saturated. There's no room for bromine to add across a carbon-carbon double or triple bond.
* No favorable reaction conditions: The reaction of dibromomethane and bromine would require a very strong electrophile to displace a bromide ion. Bromine itself is not a strong enough electrophile to facilitate this reaction.
What could happen instead:
* Substitution: Under specific conditions, it's *possible* for a bromide ion to be substituted by another bromine atom, but this would require a very strong base and high temperatures. The reaction would be highly unfavorable.
* No reaction: More likely, dibromomethane and bromine will not react significantly under normal conditions.
In summary: The reaction of dibromomethane with bromine is not a typical reaction. It's unlikely to produce a significant amount of product.
