Ok...so, the title compound is what is beeing worked on at the moment.

Just a few questions.

Toady is using the route of refluxing IPA and conc. HCl., with a lewis acid.
In this case, the most available one is ferric chloride. Since this decomposes in aq. solution, will it be requisite to form an alcoholic solution containing the correct molar quantity of HCl (g), or will anhydrous FeCl3 tolerate concentrated HCl (aq) without decomposition?

It is necessary to use the anhydrous salt, is it not? to the best of Toady's knowledge this is indeed the case. He needs to dry the hydrate (or does he....this is electronics-grade ferric chloride used for etching PCBs. Is this typically the hydrate, or the anhydrous salt?

(he doesn't know which he has, because it isn't actually his; he begged some from somebody else, and there is no information on the container, other than the name of the title compound)

Drying the hydrate using distillation from thionyl chloride is a known route, although producing SOCl2 could be a bit of a bugger. sulfur monochloride, or disulfur dichloride would be MUCH more accessible, although buying SOCl2 is an option if not.

Although any of those are reagents that he would far rather keep for more interesting syntheses. Is azeotropic distillation using something like an ether, or toluene/xylene an option?

Yes, thanks wizard X. Toady had already read the wikipedia article, it was the first place he looked.

He just assumed that the anhydrous salt would be required, rather than the hydrate that would come from using conc. HCl.  Every time he has read examples of lewis acids being used for such reactions, its always been the anhydrous salt.

Or is this not the case in this instance?

ZnCl2 can be dried by heating in a current of dry HCl (g) can it not?

ZnCl2 can be dried by heating in a current of dry HCl (g) can it not?

Maybe, but it's hard to say.

Perhaps you could just pitch Zn (or Fe) into dry HCl in isopropanol.

It's a bit pointless to use SOCl2 to dry ZnCl2 in this case, as SOCl2 will react directly with alcohols to give alkyl chlorides. SO2Cl2 will do the same. SOCl2 is preferred as it produces volatile SO2 and HCl, as opposed to SO3 and HCl. SO3 will react with your alcohol and provide alkyl sulfates, which complicates the workup, particularly because they are so toxic and carcinogenic - they should not be handled outside of a proper fumehood.

Contrary to what is commonly believed, SOCl2 is a little more unwieldy in the lab than SO2Cl2, despite being less electrophilic. The reason is all the products are gasses: SO2 and HCl. The primary hazard of an exothermic reaction is the conversion of the solution to a gas - explosion or splattering - so it should be clear why this deserves consideration.

Both are still seriously nasty things to work with however.

Regarding S2Cl2 and SCl2 and drying ZnCl2, it sounds like a mess. For chlorination of alcohols, Assyl would guess that, if it works at all, the workup is tedious and messy compared to the other reagents available. It also seems possible that some quantity of a sulfur mustard could be produced attempting this. Mustard gas was originally produced by the reaction of ethylene with SCl2 (believe it can be done with S2Cl2 as well, just by heating the product to eject a sulfur atom). Any dehydration of the alcohol would lead to similar chemistry. The toxicity of mustards is fairly general - so it's probably best not to attempt this, if you'd like to avoid ending up in the burn unit sprouting tumors like a sick, pink broccoli.

There's information pertinent to the synthesis query attached in:

https://the-collective.ws/forum/index.php?topic=16311.msg100110#msg100110

along with various attempts at humor    As far as preparing anhydrous Lewis Acid salts, there's attachments and other useful text posted in:

https://the-collective.ws/forum/index.php?topic=11013.msg49031#msg49031

and

https://the-collective.ws/forum/index.php?topic=10629.msg85478#msg85478

which would be enlightening if studied  The end results from the effort applied