Sciencemadness Discussion Board

Diethylene Glycol

UnintentionalChaos - 3-12-2007 at 11:16

I may feel like an idiot for asking later, but sometimes I overlook obvious things...

I have found a relatively cheap and clean source of diethylene glycol and was hoping it could stand in for regular ethylene glycol (only available to me as antifreeze with dye, water, and methanol mixed in) as a solvent for example, the depolymerization of poly(ethylene terepthalate). Is there any situation in which its use would be ill advised and is there anything interesting you can think of to do with it besides solvent use?

Sauron - 4-12-2007 at 09:50

Diethylene glycol is a glycol ether, right?

O(CH2CH2OH)2

Aka bis(2-hydroxyethyl) ether.

Never use it in any reaction where it might be halogenated. The corresponding bis(2-chloroethyl)ether is the oxygen analog of sulfur mustard and is a potent vesicant and carcinogen, although less so than the S-compound.

You might want to compare its bp with that of ethylene glycol. But in general its solvent properties ought to be similar as it is both a glycol and an ether.

The bromo compound is also quite nasty.

[Edited on 5-12-2007 by Sauron]

UnintentionalChaos - 4-12-2007 at 15:47

Thank you Sauron. That's the kind of "avoiding stupid mistakes" information i was looking for. I'll keep hydrogen halides out of it altogether. The boiling point is about 50C higher than regular ethylene glycol. I figured the solvent properties could be interesting.

Sauron - 4-12-2007 at 19:39

50 C higher than ethylene glycol is quite high. Not a solvent you will rotavap off!

Ethylene glycol is hygroscopic as hell, diethylene glycol may also be and that may make your life miserable if you use either in reactions that you want to keep dry. You may also want to look into azeotropes of these glycols and water.

In short you may end up with a very difficultly seperated mess.

HCl and HBr dry or aqueous need to be shunned as well as all of the usual chlorinating agents and brominating agents, anything that can replace -OH with -X (X = Cl, Br) Do not exempt F and I from this. Same goes for pseudohalogens like -CN.

not_important - 4-12-2007 at 20:18

Di- an tri- ethylene glycols, and their mono-ethers, have been used in solvents in several semi-micro org chem lab books; the high boiling points leading to shorter reaction times.

The Huang-Minlon modification of the Wolff-Kishner reaction is often run in diethylene glycol. The N-ethylene glycohol are often useful for reactions involving bases or neutral salts, the form weak complexes with metal ions and so function a bit like crown ethers.


Reagents and products soluble in alkanes can be extracted from DEG by petroleum ether, sometimes along with the addition of a small amount of water or by first adding a water-ethanol mix to the DEG reaction mix. The petroleum ether extracts are washed with water to remove and DEG, and then evaporated.

For some reactions the product is low enough boiling that it is distilled from the reaction as it is formed.


oxidation use NaOCl with DEG as the organic solvent:
http://www.mdpi.net/molecules/papers/80300318.pdf

UnintentionalChaos - 4-12-2007 at 22:10

Thank you again for your insight Sauron.

Very interesting material not_important.

Wild speculation here: Do you think diethylene glycol could be heated with conc. sulfuric acid (analagous to ether synthesis) to form a mixture of 1,4-dioxane, assorted crown ethers, and of course polymerized poly(ethylene glycol) crap. Since they are already double units, 12-crown-4 and 18-crown-6 would predominate. I think the boiling points are different enough to seperate the products somewhat easily, although vacuum distillation might be necessary. The boiling points I found for the crown ethers were all for vacuum distillation and probably for good reason...Any reason to pursue diglyme synthesis?

smuv - 6-12-2007 at 10:22

Maybe of limited help but I'll post it anyways
Quote:
Even more markedly than was the case with monoethylene glycol, the chemistry of polyethylene glycols is the chemistry of isolated hydroxyl groups and isolated ether groups. Even the simplest cyclic acetal involving both hydroxyl groups of diethylene glycol would require a ring containing eight atoms. Understandably therefore, the formation of cyclic compounds is much less a part of the chemistry of the higher polyethylene glycols. In general, review of the chemistry of these compounds here is unnecessary.


Quote:
Commercially useful procedures for preparing dioxane include the dehydration of ethylene glycol, polyethylene glycols and the corresponding ethers over acidic catalysts such as sulphuric acid, hydrochloric acid, zinc chloride, phosphoric acid, benzenesulphonic acid, and ferrous sulphate.


From 'Ethylene and Industrial Derivatives' by Miller