What type of fission occurs when Br reacts with alkanes?

When bromine (Br) reacts with alkanes, the process typically involves homolytic fission. In homolytic fission, the bond between two identical atoms, such as the bromine atoms in Br2, breaks evenly, resulting in the formation of two free radicals. Each bromine atom retains one of the bonding electrons, creating two bromine radicals (Br·).

In the context of alkanes, these bromine radicals can then react with the alkane to initiate a chain reaction through free radical substitution. This is a key mechanism in the halogenation of alkanes. The formed bromine radicals can abstract hydrogen atoms from the alkane, forming alkyl radicals, which can further react with additional bromine molecules, leading to various substitution products.

The choice of homolytic fission is consistent with this reaction pathway, as it correctly describes how the bromine molecules break apart to allow the bromination of alkanes to occur through radical mechanisms.