The hydrogenation of alkenes to alkanes is exothermic. Hydrogenation of alkenes produces the corresponding alkanes. The B-B bond adds across alkenes and alkynes to give the 1,2-diborylated alkanes and alkenes. For example, alkenes can be reduced to alkanes, or formaldehyde to methanol. Alkyl halides are reduced by samarium iodide to the corresponding alkanes. Pincer complexes catalyze the dehydrogenation of alkanes. Branched alkanes have a lower biodegradability than unbranched alkanes. From pentane to octane the alkanes are highly volatile liquids. APG is primarily a mixture of hydrocarbon molecules that are classified as alkanes. Fuel oil is made of long hydrocarbon chains, particularly alkanes, cycloalkanes, and aromatics. It also contains small amounts of ethane, propane, butane, some heavier alkanes, and nitrogen. Branched-chain alkanes are called isoparaffins. Carbonium ions can be thought of as protonated alkanes. Perfluoroalkoxy alkanes (PFA) are fluoropolymers. Haloalkanes are better solvents than the corresponding alkanes because of their increased polarity.