The gaseous alkanes, olefins, a process for conversion to high molecular weight hydrocarbons or mixtures thereof, the gaseous feed containing alkanes to form alkyl bromides and hydrobromic, thermal or it may be reacted with catalytically dry bromine vapor. Polybrominated alkanes present in the alkyl bromides, so as to form an brominated species may be further reacted with methane over a suitable catalyst. Then, a mixture of alkyl bromides and hydrogen bromide, olefins, high molecular weight hydrocarbons or mixtures thereof, and may be reacted with a suitable catalyst or in a temperature sufficient to form hydrogen bromide. Various methods and reaction, to remove the hydrogen bromide from the higher molecular weight hydrocarbons, to produce bromine from hydrogen bromide for use in the process, bromine and storage for use in the process, after to release, and brominated step is disclosed to selectively form a mono-brominated alkanes.