Now theres a bugger. Looks like the synthesis of that diphosphorus tetraiodide is quite easy, by a spontaneous disproportionation reaction of the unstable phosphorus triiodide in dry diethyl ether, to afford a solid, albeit water-sensitive, tractable solid crystalline reagent.
The phosphorus triiodide is easy enough, starting from red phosphorus and iodine. I am a BIT short on iodine, but only in the sense of its getting to be time to buy another couple of kg and bung it in the chemicals fridge, and use up what I have from my last tub full of I2. It isn't stable in the sense of being suitable for preparation of PI3 and keeping it in a bottle on the shelf, rather, its typically made in-situ due to its not being too stable, but its synthesis itself is easy, and in the case of P2I4, we WANT it to be unstable, otherwise it wouldn't disproportionate now, would it
But making it isn't difficult. Its the reagent formed in-situ by meth cooks reducing pseudoephedrine with elemental (red) phosphorus and iodine, kicked off by just a trace of water to allow the reaction to first begin. And preparing it (although I've never done so in an ethereal solvent mind you) is very easy, by simply mixing together elemental iodine and the red allotrope of phosphorus. I've still got most of 2kg of red P, bought at a discount since I took advantage of the opportunity to grab some in bulk and took more than their 1kg minimum quantity order; that I picked up for two reasons, mostly for making other phosphorus-based reagents such as phosphorus trichloride, phosphorus pentachloride and the other halides of that sort and other less well known but still potentially very useful phosphorus-requiring reagents (its probably my favourite chemical element too, due to its A-having such a huge variety of interesting allotropic forms of the element with such widely differing physical and chemical properties, from the flammable, but not acutely particularly toxic red phosphorus, to the deadly-poisonous [about as toxic on a weight basis as potassium cyanide] white phosphorus, a waxy, soft solid which can be cut with a knife like a piece of cheese, and which if not stored under water, or other suitable containment, spontaneously bursts into a blinding white flaring flame with a lurid greenish tinge, due to the fact that it is the source of the word 'phosphorescence' and glows in the dark, in either small quantities too small to, or if in larger amounts, before it has had time to burst into flames, with a green glow that in the dark, one can write on paper with a stick with a blob of white phosphorus on the end and watch the writing appear, before finally igniting and burning the letters through the paper, to the black allotropes, nontoxic, not a flame hazard, difficult and demanding to make, and black, and taking on a layer-structure in sheets of phosphorus atoms, akin to graphite, and like graphite, possessed of electrical conductivity, to violet phosphorus, which isn't very well known, and takes quite some effort from what I've read, to make it, the easiest way, apparently being to sandwich red phosphorus between layers of lead metal, under inert gas, potentially with trace levels of doping chemicals as a catalyst in the phosphorus, hold it for at least 24 hours under molten lead, and then slowly, slowly, a few degrees at a time, recrystallize it from the molten lead before finally dissolving away the lead once cooled using nitric acid..been planning to prepare samples of them all, as display pieces for a periodic table showcase, red phosphorus obviously being first, since that takes no more preparation of a sample than putting some in a vial, under some inert gas then sealing the ampoule. Then white, in its various cubic, monoclinic etc. forms, that I can begin with as the first needing any effort more than pouring some out of a tub of something I already have, by heating red phosphorus under dry inert gas in a retort, using a blowtorch, and distilling it out into a long, deep column filled with ice-cold water topped off with a slurry of salted ice to condense the phosphorus vapors, then finally, cleaning off the oxides that make it white, which, I have read of someone doing, using a dichromate-concentrated sulfuric acid bath, then cleaning away the acid carefully by remelting under water, removing oxidizing agents..I want to see if I can prepare a crystal-clear sample like that and actually have it STAY that way, by doing the whole cleanup in boiled then vacuum-degassed, vacuum-distilled and argon-sparged ultrapure water, then ampouling it, after dessication, by carefully remelting it as many times as needed whilst standing over phosphorus pentoxide, a truly nutty-strong dehydrating agent, capable even of intramolecular dehydration of anhydrous sulfuric acid to form SO3, but without oxidizing properties, and finally sealing the amp under inert gas after repeatedly vacuum-purging a chamber built for the purpose, possibly using electrical heating to melt the glass of the amp neck....it would just be really neat if its possible to have a sample of ultra-pure WP that has been cleaned so thoroughly that the white color disappears and instead what is left, is clear, and have it storable. Using glass with additives to block ultraviolet light if needs be, which contributes seemingly to the normal discoloration of regular-purity white P.
As for my P2I4 synthesis, for dehydration-cyanidation of a carboxylic acid to a nitrile (nitriles are organic cyanides), which is a rather unusual type of reaction, but definitely a very neat one, and all the more so if I need no ionic cyanides at any point, for obvious reasons)....very slick. The one downside...looks like I need to run it in anhydrous carbon disulfide. I should be able to get some, and dry it. BUT...its not easy to obtain, even for me, via buying it. It doesn't seem to come up on ebay either, not for want of looking. Its toxic, it smells foul unless very, very pure due to thiophene impurities, when extremely pure it is said to smell ether-like, although I've no desire to inhale any to find out. And it is the mother of satan when it comes to flammability. Never worked with it, but from what I have read, dipping a glass rod in hot water, and touching the warmed glass rod to some CS2 is sufficient to ignite it. It isn't actually pyrophoric, per se, just has a ludicrously low temperature at which it will catch fire, needing only to be warm, no flames or sparks or static discharge needed, just a warm glass rod, at a temperature which wouldn't even burn human skin and enough oxygen to allow combustion to take place.
Although the dehydration-cyanidation reaction of the diarylalkyl carboxylic acid to form the corresponding nitrile intermediate I have in mind can be run in certain other solvents, most notably carbon tetrachloride (which I'd either have to put some significant effort into making from scratch, probably via chlorinating chloroform, which if I didn't buy or have someone wishing to trade me reagents for some chloroform, benzene and a couple of other things, I'd make by means of the haloform reaction, using sodium hypochlorite and caustic alkali such as lye or caustic potash [NaOH/KOH respectively] on acetone as the substrate. Yields aren't wunderbar, and it takes a large volume of liquid to prepare a decent volume of chloroform that way, and it is quite an exothermic reaction, gets pretty hot whilst its cooking up one's chloroform from scratch, but it could be the ideal baptism for my new 4-neck 5 liter flask
And it isn't like bleach and caustic are expensive, or acetone for that matter. And I already have some acetone, and can easily buy more if I want, got plenty of caustic soda and a kg of caustic potash [I use NaOH a LOT, but relatively little KOH, primarily I keep it around for either occasional use when NaOH isn't quite strong enough to deprotonate something in need of deprotonation but KOH will do so, without having to resort to alkoxides, sodamide, potassium hydride [from weaker to stronger and increasingly dangerously reactive in > order, to say nothing of increasing stepwise in the same order in terms of being difficult to make or buy and more expensive to do either. Generally effort goes up in every sense there*
*actually I have a theory. That there is actually a linear relationship between how useful a chemical is and how expensive, difficult to find or make, and dangerous it is likely to be. The how low-use a given chemical is, being inversely proportional to the summed modalities of difficulty x cost+rarity.
I don't think it'd make for a uni thesis, but I've a distinct hunch that I am in fact, correct there. The more useful it is, the more its going to cost you and the bigger the ache in the bollocks it will be to make any, the lower your yields and the more dangerous the process is going to be, and the more flammable, poisonous, corrosive, difficult to contain, foul-smelling, foul tempered and the greater the likelihood of it being pyrophoric the end product will be.
In the case of CS2..the production process involves passing sulfur in vaporized, gaseous form through a tube furnace packed with coke as a carbon source and heating it to several hundred degrees, accompanied by an input of inert gas to prevent its just igniting, then carefully, meticulously condensing the searing hot carbon disulfide vapor down from red-hot coke temperature to room temperature or preferably below it as much as possible, before distilling it under inert atmosphere with a warm-water bath. Sulfur is a total pain in the arse if you need it in gaseous form, because whilst melting, it gets thick and viscous, like thickened motor oil, and there is bugger all way I'm using any of my lab glass to vaporise it from.
Instead if I have to make some for the solvent in my P2I4 R-COOH>R-C=-N inorganic cyanide free cyanidation reaction. I'll weld up a disposable metal still that I can fill up, torch from the outside or electrically heat, with a thin pipe connection with a one-way valve away from the heat to avoid melting it, that I can hook up to a cylinder of argon and a regulator, since the CS2 is hard to buy (not sure about price, I've never bought carbon disulfide before, or made it, or worked with it.
Only experience of it is reading of its properties and character, it'll be a new one on me, short of having my nose in a chemistry textbook or journal reference. Not a first date I entirely look forward to. But, all the same, it does have its niche, specialist uses, and also it acts as an excellent solvent for sulfur, or for white phosphorus
[although a solution of WP in such a volatile and flammable, rapidly evaporating solvent is also a pretty incendiary kettle of fish to deal with and require the utmost care to be taken in preparation, use and handling of it, not something I'd even make up and keep, but rather, prepare, if ever I need WP in CS2, just the quantity that I am going to require then and there for a specific task at hand, make it and use it, so as to have no leftovers of such a volatile and dangerous mixture of toxic, pyrophoric WP in a toxic solvent with a hell of a low boiling point and that needs very little encouragement whatsoever to catch fire without anything else in it]
After that though it looks alright. Once the CS2 is in hand, and the organocyanide is formed, reportedly within a couple of hours, at room temperature when conducted in carbon disulfide, with yields up to 90% for some substrates and typically at least 80something percent, then distillation and recycling of the carbon disulfide will be a piece of piss, given the insanely low boiling point, and that distillations under inert gas (or vacuum distillation, but I'll do it under inert gas because vac distillation lowers the boiling point of whatever it is thats being distilled, which is often as not, the entire point of doing it under vacuum in the first place) are nothing new to me.
Followed by one of the reductions of nitriles to primary amines in the literature, whichever after some research and digging around seems to be likely to provide the highest yield of the primary amine intermediate. First potential candidate being in-situ formation of STAB (Na triacetoxyborohydride) from sodium borohydride (got plenty NaBH4 so no need to buy any more yet, got it stored under argon, in solid 1g-unit tablet form so less surface area to react with oxygen, the bottle of NaBH4 tablets itself, stored in the same metal outer can it came in from the factory, with the top cut out, and replaced by an improvised air shield consisting of the bubble-wrap pouch that a piece of my glassware came in stretched over the outer rim of the end of the metal can, the can itself, like the bottle, being purged with dry argon) NaBH4 already has a good shelf life too, its a lot more tractable and stable than most hydride reducing agents, to the point that it isn't even pyrophoric, and can even in some cases be used in aqueous or partially aqueous solvent systems! whereas say, sodium hydride, if a spatula-full be thrown at arm's length, whilst wearing a blast shield and goggles etc., into a bucket of water, then the result is an instantaneous decomposition, a sodding great plume of hydrogen and potentially catching fire, taking the hydrogen with it. The 'potentially' being a matter of only a spatula tip being thrown into the water. Larger amounts in contact with water, or atmospheric moisture are going to violently burst into flames and a large evolution of flammable hydrogen gas. Needless to say it needs very cautious storage and handling. Borohydride is pretty damn tame, compared. Although it bucks the trend of my little hypothesis about the linear relationship between price+propensity to bite your face off and crap on your skinless screaming skull afterwards, since its still really, really useful stuff for a large variety of uses. Not the easiest of reagents to buy but easy enough that ebay can often be a viable source
Once the nitrile is reduced to the corresponding primary amine via whatever route is eventually chosen as seeming best after research, the final step is, for the main end target (I've two, possibly three that I consider worth directing research time and resources at), reductive di-methylation to a tertiary amine. Not usually the easiest reaction, to react a primary amine and end up with either secondary or tertiary amines, sec.amines being particularly hard; because they become progressively more nucleophilic as they go from primary through secondary and most of all, tertiary amines, and its really easy, and in most reactions the result is peralkylation all the way to the quaternary ammonium salt. It is possible to effect dequaternization reactions, in some cases at least but thats one more step and ergo, less yield and more cleaning up to do.
But since this is a methylation, for the main target of interest, I plan to form an imine using excess formaldehyde and HCOOH as a hydrogen donor to go direct to the tertiary amine forming an intermediate secondary amine in the process via a subsequent imine or iminium ion, but its transient as the reaction goes on without isolating the 2' amine to afford the methylated tertiary desired. That is known as Eschweiler-Clarke methylation, and ends without quaternization since it relies on the formation of an imine or iminium species and the tertiary amine cannot form one, unlike a primary or secondary amine, so thusly that undesired, and usually significant or complete quaternization of the starting amine. And from then, after the Eschweiler-Clarke, its a matter of cleaning and recrystallizing to the desired standard of purity, and performing the usual analytical tests such as either TLC or paper chromatography and melting point tests of various salts, the freebase etc. on samples of a few milligrams a piece, packed into a microcapillary tube, strapped to a thermometer at the top with a rubber band and immersed in the oil filling of my Thiele tube. Once it passes my tests for purity, then my labors will be complete, and my target compound will be there, finished and sparkling clean as a pretty pile of crystals
And as far as the overall scheme goes, the end compound is known, and data like melting point, TLC RF values etc. are known, but the actual reaction I designed myself.
(
https://en.wikipedia.org/wiki/Thiele_tube)
