plastics
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Methyl thiocyanate
I am attempting the synthesis of methyl thiocyanate as a precursor for cyanuric chloride (TCT).
There are many references to the thiocyanate on this board and its subsequent chlorination to TCT (especially by Sauron) but no detailed synthesis
http://www.sciencemadness.org/talk/viewthread.php?tid=8866&a...
http://www.sciencemadness.org/whisper/viewthread.php?tid=833...
I chose the addition of methyl iodide to potassium thiocyanate in ethanol. I have access to
potassium thiocyanate and have synthesised a fair quantity of methyl iodide from potassium
iodide, methanol and phosphoric acid (ref http://www.sciencemadness.org/talk/viewthread.php?
tid=12475). Potassium iodide is formed during the synthesis of methyl thiocyanate and can be
conveniently recycled.
Vogel 3rd edition describes cognate preparation of n-propyl thiocyanate by addition of n-propyl
bromide to potassium thiocyanate in hot ethanol. The propyl thiocyanate being isolated by
distilling off most of the ethanol and then adding water (pp305 - 306)
Addition of methyl iodide to potassium thiocyanate results in immediate precipitation of
potassium iodide, even at room temperature, with the supernatent acquiring a yellow colour and a
smell of decaying onions. My problem now is separating off the methyl thiocyanate. Addition of
water to a small aliquot of the reaction mixture does not produce a phase separation. I am
assuming I have to reduce the volume of ethanol by distilling it off. Unfortunately various
online references describe the thermal instability of methyl thiocyanate with the formation of
methyl isothiocyanate (not something I want)
http://en.wikipedia.org/wiki/Methyl_isothiocyanate
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV3...
My question is can I safely distil off the ethanol without forming methyl isothiocyanate at the
boiling point of ethanol. I would prefer not to use vacuum distillation as I have no means of
measuring or controlling the vacuum. Any other suggestions regarding the synthesis or isolation
would be gratefully appreciated
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Chemosynthesis
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I hate to bring a thread back from so long ago, but no one answered this. Ullman's Fine Chemicals Vol. 1 claims that isomerization of methyl
thiocyanate occurs above 100 degrees Celsius, so the OP should have been fine with standard laboratory pressure distillation.
Since you still appear to be an active member, what did you end up doing?
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Scr0t
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I'm interested in how far you got with this too as I hope to attempt this in few months time but with MeBr instead en route to TCT.
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jock88
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IMO
There is absolutely nothing wrong with bringing up an old thread.
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plastics
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Exactly. Three years to have a reply posted to one of my threads is pretty good going!
At the time I was looking to synthesise methyl thiocyanate as a precursor to TCT and then oxalyl chloride and other acyl chlorides.
I didn't get much past the stage described above ie methyl iodide + potassium thiocyanate = something smelling of rotting onions/garlic.
Times have moved on and I managed to get hold of TCT and oxalyl chloride, so the need to synthesise methyl thiocyanate passed
Interested to know if anyone else has attempted it however.
[Edited on 12-7-2014 by plastics]
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