Sciencemadness Discussion Board

Would some alkyl amines have the same properties as ammonia?

JefferyH - 13-9-2014 at 08:44

I'm trying to find an alternative to using liquid ammonia for reactions. Liquid ammonia being used to dissolve various ionic salts. Would I get a similar functionality if I used one of the propylamine derivatives, like isopropylamine, diisopropylamine, or propylamine? Or would these not be able to have the same ionic dissolving power that ammonia has?

If possible I would want to use something like Triethylamine since it lacks free hydrogen, but I'm not sure of its polar properties in comparison to ammonia.

I assumed this would be intuitive since they are all polar, but I haven't found any papers using alkyl amines in place of liquid ammonia.

[Edited on 13-9-2014 by JefferyH]

deltaH - 13-9-2014 at 10:42

You may want to consider using ethylenediamine or formamide.

JefferyH - 13-9-2014 at 10:56

I forgot to mention I still plan to be cooling the reaction mix to well into negative celcius, so those two are out of the question.

Triethylamine seems like it may be optimal since it doesn't have nitrogenous free hydrogen.... Do you think this would inhibit its ability to dissolve ionics?

deltaH - 13-9-2014 at 22:49

Alkyl groups larger than methyl significantly reduce the polarity of these liquids AFAIK. Speculatively, I don't think you will get joy from triethylamine or higher alkylamine.

The details you provide are scant, but you may want to consider polyethers. Glymes, such as dimethoxyethane (DME), are powerful coordinating aprotic solvents. Crown ethers are even more so (though costly) and will handle alkali salts for you.

Propylene carbonate (PC) is a VERY polar aprotic solvent that has a low melting point (-49C).

You may also experiment with solutions of solvents, for example, a mix of a coordinating ether like DME and PC. Such combos are often used in lithium batteries, though I think they usually use ethylene carbonate... but 'same difference' ;)

JefferyH - 14-9-2014 at 05:59

I will consider those. I need to consider if a solvent can survive very strong reaction conditions (very electrophilic or nucleophilic environment). In spite of ammonias nucleophilicity, it tolerates quite well in some electrophilic environments. dimethxyoxyethane could work. I will have to do some research into that.

I'm going to go on the search for a list of polar aprotic solvents.... if you have a link you might can recommend

[Edited on 14-9-2014 by JefferyH]

macckone - 14-9-2014 at 10:24

No single solvent is going to be as versatile as liquid ammonia.

DraconicAcid - 14-9-2014 at 11:22

Quote: Originally posted by JefferyH  
I'm trying to find an alternative to using liquid ammonia for reactions. Liquid ammonia being used to dissolve various ionic salts. Would I get a similar functionality if I used one of the propylamine derivatives, like isopropylamine, diisopropylamine, or propylamine? Or would these not be able to have the same ionic dissolving power that ammonia has?

If possible I would want to use something like Triethylamine since it lacks free hydrogen, but I'm not sure of its polar properties in comparison to ammonia.

I assumed this would be intuitive since they are all polar, but I haven't found any papers using alkyl amines in place of liquid ammonia.


Ask yourself- does isopropanol have the same solvent properties as water? If not, why not? How about diethyl ether?