Sciencemadness Discussion Board - Solvent choice for Phenyl Isocyanide synthesis, and polymerization inhibitor

Solvent choice for Phenyl Isocyanide synthesis, and polymerization inhibitor

Rhodanide - 22-1-2018 at 10:33

Hi all,
I've been looking more and more into refining the synthesis of Phenyl Isocyanide/Isonitrile/Carbylamine. (Hereon out I will refer to this compound as PhNC.) I have the process and it works well, but I've run into a few things. From what I've read, PhNC decomposes in the presence of water (To form what, I haven't found out. Ideas are welcomed). The problem is, the reaction that I carry out is both Aniline and Chloroform dissolved in either a 90/10 or 80/20 mixture of Denatured EtOH and water. I've found that, if water is not present, nothing is formed. Are there any alternative solvents, which are commonly available (this includes purchasing it online through a source which does NOT exclusively cater to registered businesses or labs)?
Are there any other ways to minimize decomposition upon formation, and subsequent yield loss?

Secondly, I've noticed that it seems to darken, which I think is it slowly polymerizing. How would I stop this? What are some common inhibitors? I'm not experienced in that field.

Admins and/or Mods, feel free to move this to Organic Chemistry if you feel it is more suited to that thread.

Thanks,
-R/T

LearnedAmateur - 22-1-2018 at 13:20

Isocyanides react with nucleophiles to form imines, so that’s what’s happening with the water. Also means you can’t use alcohols as the solvent either since they’ll react in the same way. What about cyclohexane, toluene, or xylene? I’m new to isocyanide chemistry, but from what I understand, the reaction is at the triple bond so aromatic systems should be unaffected..

Tsjerk - 23-1-2018 at 01:18

It sounds like water is a catalyst/solvent here, so maybe use water saturated chloroform as solvent for aniline and let this stir with baked KOH?

KOH usually is 85% with the remaining 15% being water, but you can get rid of the water by baking it.

Rhodanide - 23-1-2018 at 13:40

Quote: Originally posted by LearnedAmateur

Isocyanides react with nucleophiles to form imines, so that’s what’s happening with the water. Also means you can’t use alcohols as the solvent either since they’ll react in the same way. What about cyclohexane, toluene, or xylene? I’m new to isocyanide chemistry, but from what I understand, the reaction is at the triple bond so aromatic systems should be unaffected..

I'm not so sure about the alcohol part as you said it, because the Carbylamine reaction/Hoffman's Isocyanide test requires "alcoholic Potassium Hydroxide and Chloroform" (which react with the "analyte").
Also, I don't think that using Toluene/Xylene/Cyclohexane would be a good idea, seeing as there seems to be a need for the presence of a small amount of water as a catalyst.

LearnedAmateur - 24-1-2018 at 07:16

My bad, I was just going off this document I found: http://gbdong.cm.utexas.edu/seminar/old/Isocyanide%20Chemist...

KOH reacts with alcohols to form the alkoxide, and smaller alkoxides are great nucleophiles so I must be mistaken by my assumptions.