06-06-02 15:34
No 318233
pretreatment of wood meal(with acetone) followed
by oxidaions with nitrobenzene or CuO are
described in detail (with NaOH in pressure bomb,
then NaOH followed by continuous extraction
with chloroform)
as syringaldehyde sources are named:
birch wood, aspen wood (populus tremuloides)
and others.
obtained is a mixture of oxidation compunds:
yield of syringaldehyde via the nitrobenzene
route is 30% and 20% with CuO oxidation.
the main byproduct is vanillin.
the separation sounds complicated and
it looks like chromatography can't be avoided.
page 301-321("nitrobenzene and cupric oxide oxidations")
"methods in lignin chemistry"
springer series in wood science, 1992
stephen y lin, carlton w dence
ISBN 3-540-50295-5 springer (berlin)
ISBN 0-387-50295-5 springer (new york)
(Stoni's sexual toy)
06-06-02 17:00
No 318258
I've done nitrobenzene oxidations of certain lignins for analytical purposes. Yields are low unless you do this under pressure.
I'm not fat just horizontally disproportionate.
(Official Hive Translator)
06-06-02 18:38
No 318276
I like the CuO idea. It just sounds promising. I remember me posting recently a procedure for splitting double bonds into aldehydes w/it - not exactly the same, but in the patent they say that CuO is especially good since its oxidation potential is just fit to carry it to the aldehyde stage and not more.
Can you (or somebee else) give us more details on using CuO in that rxn? Does it proceed well at atm. pressure?
BTW, 3base, i find the amount and quality of the procs you recently submitted to the Hive very impressive, my deep respects to you
Antoncho
(Old P2P Cook)
06-06-02 19:54
No 318290
Post 214730 (halfapint: "The Hibbert Ketones of Lignin", Novel Discourse)
Post 190600 (halfapint: "Lignin Syringaldehyde Again", Novel Discourse)
Post 190973 (not existing)
Post 165712 (drone 342: "Need full article - anyone?", Chemistry Discourse)
(Hive Bee)
06-07-02 11:00
No 318521
> BTW, 3base, i find the amount and quality of the procs you recently
> submitted to the Hive very impressive, my deep respects to you
3base enjoys a lot these pleasant words of laud, thank you Antoncho
(Ubiquitous Precursor Medal Winner)
06-12-02 17:23
No 320254
Terbium's ref to Post 190973 (not existing) and also Rhodium's link to which it points, are now sadly invalid. College teachers move away, and their webs vanish. This is most unfortunate in this case, since Prof. Elder's work was the first plain description I saw to point me through the complex maze of lignin chemistry. In fact, I saved substantial portions of it. This is still helpful to me, for I still need a road map in that particular maze: I'm not out of the woods yet.
The syringaldehyde/vanillin production project from wood lignin turned out to bee over my head, under the conditions I was working: no analytical capability, and only a vague comprehension of what had to get done. Not that I gave up, but the brute force experimental methods I used just weren't producing. I would just have needed to get extremely lucky in selecting a particular technique, in order to give a repeatable method worth reporting and standardizing on. Well I keep plugging away on this problem sporadically, because I think it's my most important potential contribution to the Hive.
Just last night, I was rereading some of Prof. Elder's work I saved locally, and came up with a new approach which may bee worth trying: alkaline oxidation with KMnO4. This has given me aldehydes from piperine, asarone, etc., though not in boastful yields. In fact, nowadays I have a whole slew of oxidation methods I haven't tried on lignin. One of them is going to put out a clean and easily separated product, to reward my early collaboration with Antoncho in this matter, and then we're gonna kick some ass.
a half a pints a half a pound a half a world a half a round
Sidearm n. Flask neck tube.
(LabChamp)
06-17-02 11:57
No 322395
A few years ago a project was tried to obtaine aldehydes by oxidation of Lignin by CuO/NaOH. Powdered bagas lignin (technical product obtained by acid hydrolysis of sugar cane waste) is known to produce mixture of syringaldehyde, vanillin and p-hydroxybenzaldehyde upon partial oxidation. This reaction was tried by refluxing alkaline solution of lignin with CuO under atmospheric pressure. After acidification and extrationwas obtained a small amount of residue with vanilla smell. The residue was analysed and was confirmed that contains mainly cca 11% p-OHB, 16% vanillin, 42% Syr. But the total amount of aldehydes was so small that the project was considered not suitable for a kitchen production and abandonied. May bee interesting (but allready quite on industrial scale) would be oxidation of alkaline craft liquors by air/O2 in an oxidation tower (under atmospheric pressure, countercurrent flow of liquors and air) Have some patents available for this approach if somebody is interested.
(Stranger)
06-18-02 05:20
No 322621
Wouldn't it be much cheaper and faster to buy vanillin? I know, I know: "but where is the sport in that?". But wouldn't your limited energies and resources be better spent converting already chemically pure vanillin into more interesting things, rather than wasting huge amounts of chemicals, time, energy, and brain cells tring to turn a pile of woodchips into the world's most ubiquitous flavoring agent -- something that's sold by the metric ton on an hourly basis? I mean, come on: it's not like the stuff is really hard to get, people! We're talking about cheaper-than-dirt vanillin here, not plutonium or ergotamine (yes, in bulk it is literally cheaper than dirt.) Just plain vanillin (pun intended.) Why are you handicapping yourself? Where is the sense in all of this busywork?!
Save yourself a huge amount of time and energy, buy the stuff, and then investigate reactions where vanillin is the starting material: such pursuits are far more rewarding, and a lot closer to whatever final product you're interested in (and no doubt, there are several products that immediately spring to mind.)
Please, just think it over.
-anton_berg
(Old P2P Cook)
06-18-02 05:39
No 322623
Wouldn't it be much cheaper and faster to buy vanillin?
Ummm, wasn't this thread about syringealdehyde? So what are you ranting about?
(Stranger)
06-19-02 13:05
No 323031
Yes, syringaldehyde is the topic, and I guess I didn't make myself clear.
What's being proposed is taking a big pile of saw dust or wood chips or whatever, soaking it with acetone, then pressure cooking it with lye, nitrobenzene, etc. (incidentally, every pressure cooker I've seen has been made from aluminum; if anybody attempted to fill it with nitrobenzene and lye and heat it under pressure, imagine the mess created when the lye corrodes the walls of the pressure cooker and hot, semi-explosive nitrobenzene comes shooting out all over the place.) When the reaction is complete, you're left with a great big stinking mess (don't forget that aniline is generated in the reaction, since nitrobenzne is both the solvent and the reagent) that you'll need to do a work-up on, first to extract the aldehydes, and then you'll need find a way to efficiently separate vanillin and syringaldehyde. In the end, which would be a long time from when you started, under ideal conditions, you'll be left with a huge pile of waste to deal with, and hopefully a tiny pile of your final product. This seems entirely too messy and too complicated, especially considering the amounts of syringealdehyde that may be needed later on, depending on how ambitious a person is.
What I'm suggesting is this:
Vanillin -> 5-bromo- or 5-chlorovanillin -> syringealdehyde.
I believe this to be the more sensible alternative. Vanillin is brominated or chorinated using hydrogen peroxide, acid, and an appropriate bromide or chloride salt. 5-halovanillin is methoxylated using sodium methoxide and copper salt catalyst in ethyl acetate. Yields are good, details can be found on Rhodium's chemistry page.
Yes, it's not purely OTC, but then again I haven't found a OTC source for nitrobenzene or chloroform around where I live either. In any case, the chemicals for the vanillin->->syringaldehyde route are not especially unobtainable. The reaction volume is going to be much, much smaller, far less waste is generated, it will cost less time and money, and it doesn't involve anything like heating a caustic slurry of sawdust and quasi-rocket fuel under pressure...
But hey, if that's your thing, don't let me limit you. If you really, really want to challenge yourself (all the while endangering yourself, your lab, and any of your closest neighbors), don't let me take away your dream. Just be careful; that's all I ask. Yes, be careful, and don't do it anywhere near me.
(Hive Bee)
06-19-02 23:56
No 323149
keep looking -Presto makes stainless models
OTEECEE & meeeee!!!!
(Stranger)
06-20-02 13:48
No 323326
Presto, you say? Huh. You learn something new everyday. I guess I haven't looked especially hard for one of these, but it's nice to know they're available. Thanks.
Still, and please don't be mad at me for saying this 3base, but if I live the rest of my life having never tried such an impractical, unwieldy, and pointlessly archaic synthesis, I think I'll die a happy chemist. I must admit that in a former life (about two or three years ago), I was deeply infatuated with this very synthesis too. I just knew that lignin was the future, especially considering the price of the raw material - cheaper than free, from some sources. In fact, I still believe that if this reaction were done on perhaps a multi-ton scale with the proper facilities and technology, this method would make sense. But for bench/prep/pilot plant scale, considering the amount of byproducts, the work-up, and the amount of waste generated, and the fact that isn't even OTC, I think its a challenge to justify. Yes, the suggested vanillin->->syringealdehyde route isn't quite OTC either, but gram-for-gram, you'll be buying a lot less chemicals, both in price and volume, if you use the latter route. This is one case where I think "modern" synthetic methods really are unquestionably better.
If you use nitrobenzene, you're going to have to purchase it from a chemical supply house in significant quantities not to mention the chloroform, etc. If you use CuO, you'll still need chloroform, plus you'll be making a whole lot of green, ugly, poisonous heavy metal waste that will be very hard to dispose of ethically (no, this should not go down the drain. It will cause some serious problems down at the local sewage treatment center when the concentration of aerobic bacteria drops rapidly and unexpectedly.)
(Chief Bee)
10-07-03 23:43
No 463264
(Rated as: good read)
Improved Alkaline Oxidation Process for the Production of Aldehydes (Vanillin and Syringaldehyde) from Steam-Explosion Hardwood Lignin
Guoxiong Wu, Michele Heitz, and Esteban Chornet
Ind. Eng. Chern. Res. 33, 718-723 (1994) (../rhodium/pdf /syringaldehy
Abstract
The production of aldehydes from a steam-explosion hardwood lignin is the main objective of this paper. It is demonstrated that the combined aldehydes yield (vanillin + syringaldehyde + hydroxybenzaldehyde) can reach 14.6 wt% of the lignin isolated from the steam-explosion process. This represents 12.2 wt% of the Klason lignin present in the initial hardwood (Populus tremuloides) and 2.5 wt% of the dry wood. The process steps are relatively simple: aqueous alkaline (13.5 wt% NaOH) oxidation (pure O2) of lignin in the presence of Cu2+ and Fe3+ as catalysts, at 170°C and with 10 min as reaction time. The high yields of aldehydes observed in our work far exceed those obtained in the conventional alkaline air oxidation of spent sulfite liquors. Our results support the concept that biomass-derived oxyaromatic chemicals via improved process strategies may soon challenge existing petroleum-derived routes (vanillin is currently produced via the sequence benzene
cumene phenol guaiacol vanillin).