Crystals! (or not)
October 28th, 2009 by LiqCI’m trying to grow some crystals. The compound is unstable at RT, and I’m never feeling lucky with this shit. So I’m growing it in the cold room. I really suck at this. The compound has a brick of a p-nitrobenzamide in it and I still can’t make it happen, to the amusement of both chemists and biologists with their ribosome. Over the last week one of the vials produced a lump of solid, which is promising. I decanted the supernatant and redissolved it in chloroform. Not sure why, given that chlorinated solvents aren’t the top choice for this delicate affair. I layered cyclohexane on top, and put it to chill. 15 minutes later (just looking!) I saw this:
Four layers![1] Chloroform, precipitating compound, liquid mixture of chloroform and cyclohexane, and frozen cyclohexane (mp +6.5 °C). Some red biocrap on the background for the dramatic effect. Parallel vapor diffusion trials are on the sides.
Slow solvent diffusion is the only method that I had luck with so far, so I’m trying it. I’ve got all kinds of advice on crystal growing and I can’t possibly try them all. For instance, my friend’s universal method for growing X-ray quality crystals (for fairly greasy stuff) is to heat it in cyclohexane and add ether dropwise till it dissolves, then hide it in the back of the hood, and return to harvest a few days later.
[1] Somebody told be that there’s a vessel with seven stable liquid phases in it somewhere on exhibit. Is this true?
The best we ever got was the floating blob we had in one of our waste bottles. It was the same colour as the bottom phase, and just sat there in the middle of the upper layer.
I’m not sure what happened to that bottle…
your friend is right. things crystallize best when you either forget about them and don’t need them. But, in a pinch, slow diffusion always worked best for me too. not always WORKS, but just works best. For TM complexes, layering with pentane and shoving in the back of a freezer for a few weeks works wonders.
thirded. accidental xtal growth is the best way. they can tell when you care about them growing, and they laugh at you.
I officially don’t care. There. I said it. Will they grow now?
They can sense sarcasm.
unlike mitch?
better yet, does anything anomalous happen if mitch tries to grow crystals?
or crystals try to grow mitch?
7 layers is nothing. Find a copy of Hildebrand and Scott “Regular Solutions”. Opposite the title page is a test tube with 10 liquid layers. From top to bottom: 0) air, 1)hexane, 2) aniline, 3) aqueous methyl cellulose, 4) aqueous polyvinyl alcohol, 5) aqueous mucilage, 6) silicone oil, 7) phosphorus,
fluorocarbon, 9) gallium and 10) mercury. “The caption is classic: An illustration of the problems challenging theories of solubility.”
And I thought a “Black and Tan” was good!
This is probably proprietary or private, but why are you trying to grow crystals of something unstable at RT?
LiqC you are lucky indeed. How about this (I saw it my own eyes):
Imagine you have 5-10 mg of final natural product. You have to do crystals whatever it costs. Your PI is coming every 5-10 min (no joke) and asking you about these damn crystals. After 5-7 hours he is taking half of what you have and trying to grow up crystals himself, and like this three days non-stop.
So, relax, take beer and they will grow themselves.
Wait, every day he takes a half to grow himself, fucks it up, comes back next day, takes half of what’s left, and so on? Arithmetic demon!
I got me, he took it once of course
))
was this the boss who has famously sweet tooth for eye-candy multicolor presentations?
you got it right
I am curious, who manage to grow the xtal? Candyman or the student? I know he (Candyman) has very high expectation, he said so in an interview but I never thought he is that demanding.
I’ve always found slow evaporation works the best. And by that I mean forget my sample in the NMR tube for a week or 5 and come back and have a crystal
Methacrylic ester of N-(2-hydroxyethyl)-pyrrolidinone. Acid chloride, alcohol, esterify. Shake in sep funnel and get three layers. It wasn’t any good for its intended application, either.
Keep your functionality hard by the polymer backgone. Conformational freedom is a fool’s errand.
Was it base-promoted polymerization?
The sep funnel was the monomer. Isolate, dry, 0.1% crosslinker, AIBN free radical polymerization in a silaniized vacuum ampoule. Standard output of a clear brittle polymer rod unbound to the glass. Slice 1 mm wafers with a diamond disk saw (mineral oil in trough). Lightly polish faces, micometer thickness and diameter, hydrate the hydrogel. Toss in waste crock.
Conformational freedom allows domain aggregation of functionality upon hydration. The hydrogel scatters light and is opaque. Jam functionality to the backbone: Poly(N-vinylpyrrolidinone-co-N-vinylcarbazole), Invuleron. Always polymerize neat to tension the crosslinking upon hydration.
speaking of solubility and Halloween, it’s been forever since I last made a layered soft drink.
For Halloween, you can start with half a glass of orange soda then fill the rest gently (as in over the back of a spoon) with diet cola.. great fun for the kids!
“Orange soda” triggers immediate “stop putting shit in my flasks, David Blaine!” response in me… http://www.youtube.com/watch?v=wTqsV3q7rRU
Holy shit how have I never seen this.
layered drinks are easiest done with Jello – except that every time I drink Jello shots I end up regretting the night.
LiqC, ever try using DMSO? Overhere, as a desperate attempt, we will sacrifice a small tiny tiny amount in DMSO and slowly let it diffuse over months, in a corner. Usually (3/5 so far) I got good good big big xtal.
I have to keep it cold, DMSO will freeze. Diffuse with what though?
Sorry..sorry… I must be thinking of something else, let it evaporate (very slowly…very slowly… very very loooonggggg). But since you have to keep it cold, too bad then. My buddy upstair works in a inorg lab, she always get huge nice xtal with DMSO. It’s her ju-ju
I like to use my NMR tubes for slow crystalisation. It leaves me one tube down but the diameter of the tube usually gives some nice crystals. But it is mostly due to me being too lazy to clean out my NMR tubes.
How do you get them out? Just wash them out with solvent, or do you have to break the tube?
I tap them out into a small vial or if that fails (which it usually does) I use a long thin syringe needle and slowly work them up the tube.
vapour diffusion is my method of choice. it’s even slower than layering two solvents, which might prevent precipitation.
I’m trying to find my crystals, but I misplaced the picture :S