Alkylation occurs when a molecule replaces a hydrogen atom with an alkyl group that generally comes from an organic molecule. Alkyl groups that are found naturally occurring in the environment are organometallic compounds. Organometallic compounds generally contain a methyl, ethyl, or butyl derivative which is the alkyl group that replaces the hydrogen. Other organic compounds, such as methanol, can provide alkyl groups for alkylation. Methanol is found naturally in the environment in small concentrations, and has been linked to the release from biological decomposition of waste and even a byproduct of vegetation. The following reactions are alkylations of soluble compounds found in creosote preservatives with methanol.