Digital Hepatitis
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Cyanamide from calcium cyanamide questions
Hello all:
I am a long-time lurker but first-time poster. Definitely appreciate this forum and all it's had to offer over the years.
While there's been a lot of scattered anecdotal references to cyanamide preparation (and one would think it would be easy enough to acquire since it
is available to grape farmers in 50% aqueous form [although apparently not for laymen]) I have yet to see anyone put forth anything resembling a
definitive "best way" to prepare cyanamide [or guanadine, for that matter] from the more commonly available lime-nitrogen.
I had settled on preparing cyanamide from calcium cyanamide since this reaction was about as seemingly simple as you could get. However, I ended up
mixing aluminum sulfate and calcium cyanamide in a big glass jar right before it got too cold to work on my little hobby last year. Plus, filtering
out all of the precipitated alumina, etc. ended up being way messier than I had hoped.
Here's the original procedure in question:
(from "Cyanamid Manufacture Chemistry and Uses" (p. 11)
Fresh commercial Cyanamid or better, the unhydrated lime-nitrogen, is extracted with cold water (solubility about .9 grams nitrogen in 100 cc
water). The calcium is removed either with oxalic acid or aluminum sulphate, but preferably with the latter. After removal of the calcium sulphate
and alumina by filtration, the filtrate is evaporated in vacuo below 40 and the residue extracted with ether. It can be purified by recrystallization
from ether.
First of all, I had hoped that there would be a good extraction protocol that didn't involve ether, since it is expensive, smelly, and not my favorite
thing to work with, but I'm thinking now that there's not. Cyanamide is soluble in virtually everything except the typical hydrocarbons (hexane, etc)
and there's probably going to be so much junk/particulates at the bottom of the jar unamenable to regular old filtration that it might be difficult to
purify without ether.
Second of all, how much of the filtrate should be evacuated? 90% of it? How dangerous is cyanamide either in water &/or by itself? I've read
reports that it's "dangerous' when it comes in contact with water but in light of aforementioned procedure and the fact it's sold commercially as a
50% aqueous blend I'm not sure if I'm just being overly paranoid or not.
Basically, I've got a good mol each of aluminum sulfate and calcium cyanamide swimming around in this jar, and I'm wondering if I should continue this
endeavor or just start over from scratch. Thing is, I haven't seen any other procedures that seem much better (and yes, I've looked through all of
the threads here.) Would I be better off ditching this and attempting to go for guanadine nitrate, as it is a suitable substitute?
I appreciate any advice that anyone might be able to provide!
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Zan Divine
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Mood: Wishing all the worst that life has to offer to that SOB Wayne Lapierre
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I'd give this a serious look. It's the method I'd explore first.
An efficient one-pot method for the synthesis of cyanamides from dithiocarbamate salts via a double desulfurization strategy using molecular iodine is
disclosed. Dithiocarbamates, by the action of iodine yield isothiocyanates in situ, which on treatment with aqueous NH3 give thioureas. The thioureas
so generated undergo further oxidative desulfurization with I2 giving corresponding cyanamides in good yields. Environmental benignity, cost
effectiveness and high yields are the important attributes of this one pot procedure.
The only reagents needed are iodine, Et3N and NH3(aq.).
A one-pot preparation of cyanamide from dithiocarbamate using molecular iodine
Jayashree Nath , Bhisma K. Patel , Latonglila Jamir , Upasana Bora Sinha and K. V. V. V. Satyanarayana
Green Chem., 2009,11, 1503-1506
DOI: 10.1039/B914283P
Sorry, but I don't have the full article.
Much easier than dealing with those white solids.
[Edited on 21-5-2012 by Zan Divine]
He who makes a beast of himself gets rid of some of the pain of being a man. --HST
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aaparatuss
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I hope you read Rosco Bodine comments in the
TCCA, Na-DCCA and cyanuric acid thread
if you have Calcium Cyanamide then i do have the refs that show bubbling CO2 or maybe dry ice into the aqueous solution will precipitate the Ca
Carbonate.
Vacuum evaporation should get you the molecular cyanamide.
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Digital Hepatitis
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Thanks for the response, ya'll. Actually going to go for the ether extraction of calcium cyanamide + aluminum sulfate and will let everyone know how
it goes, will post results in another week or two when this is done.
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