The cleavage of carbon-hydrogen bonds in organic compounds, leading to subsequent functionalization to introduce useful chemical groups. For example, petroleum and natural gas, important energy resources for the modern world, are both alkanes, C_nH_2n+2, with many C–H bonds. One problem is to convert these alkanes to useful alcohols, C_nH_2n+1OH. This is particularly difficult because of the lack of reactivity of alkanes as indicated by their older name, paraffins (from Latin, meaning low affinity). In C–H activation, metal catalysts are often used to mediate the hydrocarbon conversion reactions.