The Vespiary

The Hive => Chemistry Discourse => Topic started by: Antoncho on April 19, 2002, 08:06:00 PM

Title: Methoxides from CaC2 - experiences and questions
Post by: Antoncho on April 19, 2002, 08:06:00 PM
Oh my beeloved ones!

Will anyone lend SWIM a hand? As he needs one.

That's what he did: placed 62g of tech grade CaC2 in 200 ml absolute (dried over CaO for 4 days and distilled) MeOH and refluxed for ~40 hours. Naturally, an exhaust tube from the condenser's top was stuck out of the window. By the end of that time gas production almost (not quite) ceased, the said gas being at that point almost entirely H2S, judging by the odor.

Oh, yeah - theĀ  %age of the actual CaC2 in the shit was measured prior to that w/an improvised gasimeter (acetylene is 1:1 soluble in water, so 1st dissolve some carbide in your water in a closed vessel, shake till the liquid saturates w/acetylene and then use it for your gasimeter - you'll need a somewhat precise figure to know how much alkali to add later). It was found to bee 80% - which fits precisely w/the literature data, courtesy of Mountain_Girl.

The methanolic mixture w a lot of white undissolved solids in it was mixed with 77 g (~90% counting on the actual CaC2) KOH in 200 ml abs. MeOH

SWIM thought that Ca(OMe)2 will bee at least to some extent soluble in MeOH, so it would readily xchange its metoxide ion for OH-, giving insoluble Ca(OH)2 precipitate and KOMe. But...... It appeared that the shit was not soluble in methanol to a significant degree or something - at least, a quick test of the liquor, mixing it with some unh. CuCl2 in abs. MeOH, gave a blue precipitate.

SWIM dissappointedly left it in the corner, took another similar test in 24 hours - same result. HOWEVER, after standing for a week a sample of liquor produced a dark-brown precipitate. Which upon addition of water turned blue, just like a normal Cu(OH)2 should bee.

Now SWIM's in a sort of confusion - he wants to fucken know what he's got there bee4 he attempts a work-up. So, his question is:COULD ANYBODY, PLEASE, SUGGEST HIM A GOOD RELIABLE TEST for telling apart KOH from KOMe and determining the %age of each in the mixture? It would bee very preferrrable to have such a test made in methanolic solution (i.e., w/out evaporating MeOH off).

And - could anyone at least confirm that Cu(OMe)2 is actually brown (maybee, somebee w/access to Na or NaOMe and some unh. cupric salt can just check it out, please?)

As you may guess, SWIM's particular goal with this method is to get methylate substantially free from hydroxide impurities - the advantage, that the other closely related processes - namely, w/K2CO3 and NaOH/CaO, don't have.

Of course, the ultimate goal is to reanimate someday methoxylation of bromovanillin - luckily, SWIM has access to all DMF he could possibly want.

Please, help!

Title: aluminium?
Post by: element109 on April 23, 2002, 05:54:00 PM
Antoncho:This is not a direct response to you question, but I believe that the separation from hydroxide impurities is probably very difficult.

But, has anyone thought about using aluminium methoxide ?
Washing the necessary amount of Al with a Hg salt and a crystal of iodine in anhydr. MeOH, decant, wash with MeOH and let dissolve in the methanol like one does with sodium.

As soon as SWIM gets his hands on a litre of ethyl acetate he will try this.

Title: The answer.
Post by: Antoncho on April 23, 2002, 06:08:00 PM
No, i am 100% positive that it isn't possible.

See, Al(OMe)3 is principally different from the alkali or alkali earth alkoxides. It isn't ionic. Which makes it an acid - which means the alkoxies hanging from it don't have that extra electron charge, which attracts methoxy ions to the halogenated carbon at the ring and make them take away that "positron" from the bromine and through it out and take its place. The difference is roughly the same as beetween NaOH and Al(OH)3

BTW, although it is said in a patent or two that i've seen that alkali earth methoxides can bee used, i highly doubt that they will work well. at least Ca(OMe)2. It's rather insoluble and they will form even more insoluble salts w/bromovanillin.