Chemical structure of chloromethyl methyl ether.

Chloroalkyl ethers are a class of organic compounds with the general structure R-O-(CH₂)_n-Cl, characterized as an ether connected to a chloromethyl group via a alkane chain

Chloromethyl methyl ether (CMME) is an ether with the formula CH₃OCH₂Cl. It is used as an alkylating agent and industrial solvent to manufacture dodecylbenzyl chloride, water repellents, ion-exchange resins, polymers, and as a chloromethylation reagent. It is a known human carcinogen.^[1] In organic synthesis the compound is used for the introduction of the methoxymethyl (MOM) protecting group.

Closely related compounds of industrial importance are bis(chloromethyl ether) (BCME) (closely related to chemical weapon sulfur mustard)^[2] and benzyl chloromethyl ether (BOMCl).

Chloromethyl ether	R		Molar mass	CAS number	Boiling point °C
Benzyl chloromethyl ether	Benzyl		121.93	98-80-6	102°C @ 14 mmHg (1.9 kPa)
Methyl chloromethyl ether	Methyl		80.51	107-30-2	55-57
Bischloromethyl ether			114.96	542-88-1	106
t-Butoxymethyl ether	Butyl		124.5
Methoxyethoxymethyl ether			124.57	3970-21-6	50-52°C @ 13 mmHg (1.7 kPa)
Representative chloroalkyl ethers [3]

[edit] MOM ethers

Methyl chloromethyl ether (often abbreviated MOMCl) is used as a protecting group for alcohols. The product formed is a MOM ether. A base such as N,N-diisopropylethylamine is a requirement.

The MOM group can be removed by application of dilute acid.

An example is the protection of a phenol group:^[4]

With a benzyl group the protective group becomes a BOM-ether. See also the closely related methylthiomethyl ethers.

With a t-butyl group the protective group becomes a Bum-ether. The chloride is prepaired from Methyl tert-butyl ether using a photochemical chlorination.^[5]

With a methoxyethoxyl group the protective group becomes a MEM-ether. This ether is much more stable than the MOM ether to hydrolysis.

[edit] References