I've been looking for some of these sporadically here and there, and have not had any luck. Trying to do SN2 chemistry with dichlorophenylphosphine to produce diaminophosphoranes. Specifically, I'm looking for anhydrous aniline.
Jason Wilt, Aniline is available from any reagent companies in the world (for example, Merck Sigma-Aldrich, Fluorochem, Fujifilm Wako, Kanto Chemical, Kishida, Tokyo Chemical Industries, etc), but what's the exact problem for you?
Kohei Torikai Aniline is available, but as far as I can tell, already anhydrous aniline is not.
Drying amines is frankly a pain (stir over mol sieves & vacuum-distill under N2), and considering how commonly amines are used, I was quite surprised to find that common suppliers did not sell anhydrous aniline.
Phosphorus (III) compounds are notoriously water-sensitive, so I'll probably need to resume that part of my project in the glove box. Being able to buy already anhydrous primary amines and tertiary amine bases would be a huge headache off my shoulders, to be able to transport said compounds into the glove box without any added preparatory drying or degassing steps.
Jason Wilt, Haha, I understand you well, but I'm afraid you have no easier ways. Distill amines from CaH2 (under reduced pressure if the b.p. is higher than around 100 oC) under argon (or cancel the vacuum by argon or nitrogen), aliquot to many ampules and close within a second. You can keep the ampules in a fridge for several years. Basically, amines are easily damaged by light and air to decompose to turn yellow, orange, or brown, therefore, suppliers cannot keep the quality. This would be the reason you cannot find the dry ones from commercial sources. Use freshly distilled amines for your research. When I was an undergraduate students, I was also afraid of distillation and it was my big headache, because I was not used to. However, after experiencing the vacuum distillation many times in my Ph.D. study, it became just a piece of cake for me. It's a chance for you to skill up. Good luck! Cheers!
Kohei Torikai, I'm surprised that brown-glass bottles or opaque bottles in light-reflecting bags don't work to stop said light-based degradation.
It's highly irritating, but I understand. You are right in that I am not terribly used to distillation of said amines. I do have to ask - when distilling them, would the degradation products have higher or lower b.p. than the amine itself? Knowing whether that is the case would be quite the boon as I wouldn't need to bother with a multi-flask receiving setup, just distilling into a single flask.
Looks like I'll need to get some CaH2 then. Lab doesn't have that at the moment.
Jason Wilt, Because no one knows the degradation products have higher or lower boiling points than the mother amine, I recommend that you use at least two receiver flasks to eliminate both lower and higher bp materials together. Imagine you distill 25 mL, I usually take the first 3 mL and last 1-2 mL each in a same small flask together. Collect the first, low bp portion till the gas temperature becomes constant. Then, you will have a main fraction in a big flask. The gas temperature tends to decrease during the last half of your distillation, heat to keep the gas temp. It's time to stop collecting the main fraction and to change the flask to the drain receiver, if the gas temp. goes down even if the mother liquor is heated. After cooling the whole system to rt, introduce argon or nitrogen to the system, to break the vacuum. Do not dry up the mother flask. Stop the distillation before the mother, heated flask loses all the liquid, because there may be peroxides there. (Dried peroxides are said to be explosive sometimes when they meet oxygen, at high temp. That's why you should cool the system before stopping the pump. You also use argon not air. All of these avoid the danger.) Put a septum cap with an argon balloon to the main fraction, and by a syringe or a cannula, transfer the freshly distilled amine to ampules which are already dry and have argon inside. Close the ampules immediately by flame, and keep them in a dark fridge till you use them, after you warm up to rt. Refluxing with CaH2 for 1 h will usually be done before the distillation. Good luck!
- Badges
- Science topic
- Similar topics
- Chemistry