In organic chemistry, a methoxymethyl ether is a functional group with the formula ROCH2OCH3, abbreviated MOM. It is a kind of chloroalkyl ether and, like its congeners, often employed in organic synthesis to protect alcohols. They are usually derived from 2-methoxymethyl chloride. Closely related to MOM ethers are methoxyethoxymethoxy (MEM) protecting groups, introduced using 2-methoxyethoxymethyl chloride. The MEM protecting groups are more easily installed and more easily removed.

Protection

Typically, the alcohol to be protected is deprotonated with a non-nucleophilic base such as N,N-diisopropylethylamine (DIPEA) in dichloromethane followed by addition of the chloromethyl reagent. < Although not relevant to protecting groups, MOM groups are installed by reaction of chloromethyl ethers with methoxide and by the acid-catalyzed reaction of alcohols with dimethoxymethane.

Deprotection

The MOM and the MEM protecting groups can be cleaved with a range of Lewis and Bronsted acids.

Safety

Chloromethyl methyl ether and chloromethoxyethoxymethane, like other chloroalkyl ethers, are strong alkylating agents with attendant dangers. These compounds are human carcinogen.