Dimethoxymethane, also called methylal, is a colorless flammable liquid with a low boiling point, low

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

and excellent dissolving power. It has a chloroform-like odor and a pungent taste. It is the dimethyl

acetal In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...

of formaldehyde. Dimethoxymethane is soluble in three parts water and miscible with most common organic solvents.

Synthesis and structure

It can be manufactured by oxidation of methanol or by the reaction of formaldehyde with methanol. In aqueous acid, it is hydrolyzed back to formaldehyde and methanol. Due to the anomeric effect, dimethoxymethane has a preference toward the ''gauche'' conformation with respect to each of the C–O bonds, instead of the ''anti'' conformation. Since there are two C–O bonds, the most stable conformation is ''gauche''-''gauche'', which is around 7 kcal/mol more stable than the ''anti''-''anti'' conformation, while the ''gauche''-''anti'' and ''anti-gauche'' are intermediate in energy. Since it is one of the smallest molecules exhibiting this effect, which has great interest in carbohydrate chemistry, dimethoxymethane is often used for theoretical studies of the anomeric effect.

Applications

Industrially, it is primarily used as a solvent and in the manufacture of perfumes, resins, adhesives, paint strippers and protective coatings. Another application is as a gasoline-additive for increasing octane number. Dimethoxymethane can also be used for blending with diesel.

Reagent in organic synthesis

Another useful application of dimethoxymethane is to protect alcohols with a methoxymethyl (MOM) ether in organic synthesis. Dimethoxymethane can be activated with phosphorus pentoxide in dichloromethane or chloroform. This method is preferred to the use of chloromethyl methyl ether (MOMCl). Phenols can also be MOM-protected using dimethoxymethane, ''p''-toluenesulfonic acid. Alternatively, MOMCl can be generated as a solution by treating dimethoxymethane with an acyl chloride in the presence of a Lewis acid catalyst like zinc bromide: :MeOCH₂OMe + RC(=O)Cl → MeOCH₂Cl + RC(=O)(OMe)). Unlike the classical procedure, which uses formaldehyde and hydrogen chloride as starting materials, the highly carcinogenic side product bis(chloromethyl) ether is not generated.

References

External links

* {{Authority control Ether solvents Formals Methoxy compounds