TEDM - Triethylene Glycol Dimethyl Ether — Frequently Asked Questions

Because it has four ether oxygens rather than three, spaced along a flexible open chain. The strength of the interaction with a metal cation increases with the number of donor oxygens that can coordinate to it, so each additional glycol unit in the glyme series raises chelating power. Triglyme therefore dissolves and activates salts and organometallics that diglyme handles poorly.

In many applications, functionally yes, and at a fraction of the cost. A crown ether is a rigid ring pre-organised to bind a specific cation size, which makes it more selective and more powerful. A glyme is a flexible open chain that wraps around the cation instead. Where extreme selectivity is not required, triglyme achieves much of the same effect far more economically.

Above 210 degrees Celsius, which allows reactions to be run hot in a strongly solvating aprotic medium where a shorter glyme would boil off. That combination of high temperature capability with strong cation solvation is the main reason for choosing it over monoglyme or diglyme.

Yes, and particularly so given its use in high-temperature work followed by distillation. It should be supplied inhibited, stored sealed away from light, dated on receipt and tested for peroxides before distillation or evaporation to dryness, since peroxides concentrate dangerously in the residue.