Methoxide

Methoxide is an organic salt, and the smallest alkoxide.

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In Organic chemistry, the methoxide ion has a formula of CH₃O^- and is the conjugate base of methanol.

Sodium methoxide, also referred to as Sodium methylate, is a white powder when pure. It is used as an initiator of an anionic addition polymerization with ethylene oxide, forming a polyether with high molecular weight. The main application^{[citation needed]} of sodium methoxide today is the use as a catalyst in the production of biodiesel. In this process, vegetable oils or animal fats, which chemically are fatty acid triglycerides, are transesterified with methanol to give fatty acid methyl esters (FAMEs).

Sodium methoxide is produced on an industrial scale and available from a number of chemical companies. The major suppliers today are BASF, Degussa, and Interstate Chemical Company.

In biodiesel production, methoxide is incorrectly referred to as the product of mixing methanol and sodium hydroxide. This reaction produces water according to the equation

NaOH + CH₃OH -> H₂O + Na⁺ + CH₃O^-.

There is an equilibrium between CH₃O^- and OH^-: CH₃O^- + H₂O <--> CH₃OH + OH^-.

Because the addition of NaOH to CH₃OH only results in a small amount of methoxide in solution, referring to this as methoxide is less correct than saying that it is a sodium hydroxide solution in methanol.

This confusion may have arisen since methoxide is a very powerful base that has been used experimentally in several papers and seems to self perpetuate. As methoxide is a powerful base, and base transesterified biodiesel is a common method of production, the use of sodium methoxide can substantially increase yields, however it is very sensitive to water, as little as 1% in a reaction will stop it from working. Water immediately reacts with the sodium methoxide to form caustic soda (NaOH) and methanol. Since water inhibits the base catalyst, this stops transesterification taking place.

Another problem with water is that in the presence of triglycerides (from the biodiesel reaction) sodium / potassium and water when being mixed will undergo saponification (soap formation), another reason why water must be kept out of the system.

Sodium methoxide in methanol is a liquid that kills human nerve cells before any pain can be felt. In the event of contact with methoxide, rinse the contacted area with water, seek medical attention immediately.

Making sodium methoxide is dangerous, involving H₂ and lots of heat. In addition, the resultant chemical is highly toxic. For this reason, the safety of the design of your equipment and workspace should be carefully considered before use, and protective clothing and a respirator should be worn during handling. Only as much as is intended to be used immediately should be created.