glyme

Glyme is a family of polar, high-boiling di- and polyether solvents derived from the dimethyl ethers of poly(ethylene glycol). The best-known members are monoglyme, diglyme (diethylene glycol dimethyl ether), triglyme (triethylene glycol dimethyl ether), and tetraglyme (tetraethylene glycol dimethyl ether), with higher oligomers also considered glymes. They are valued for their strong solvating ability toward metal ions because of multiple ether oxygen atoms that can coordinate to cations.

Chemically, glymes are typically described as dimethyl ethers of poly(ethylene glycol) chains. The common pattern is CH3O-(CH2CH2O)n-CH3, where n corresponds to the length of the glycol backbone (for the familiar members, n ranges from 1 to 4). Increasing the chain length generally raises boiling points and viscosities while maintaining a polar, aprotic character.

Applications and uses: Glymes are widely used as solvents in organic synthesis and catalysis, especially for reactions involving metal salts or organometallic reagents that require strong cation solvation. They are also employed as electrolytes or co-solvents in electrochemistry and in some battery chemistries due to their coordinating ability and dielectric properties. In polymer chemistry, glymes can serve as solvents and, in some cases, as plasticizers.

Synthesis and handling: Glymes are produced by methylation of poly(ethylene glycol) diols or related etherification routes that convert terminal hydroxyl groups to dimethyl ethers. They are flammable liquids; exposure may irritate skin, eyes, and the respiratory tract. Proper ventilation and handling practices are advised, and some glymes may form peroxides on storage, so containers should be kept sealed and away from oxidizers.