Sciencemadness Discussion Board - furfural

furfural

Magpie - 11-3-2011 at 15:20

For those of you who love heterocyclic compounds I will describe my experiment in making furfural. I used the procedure in the forum library in Gattermann (1937).

300g of oat bran was used as substrate. This was steeped in dilute sulfuric acid then steam distilled yielding 700mL of distillate. The residue in the pot was char, easily removed. The distillate was neutralized with Na2CO3 then saturated with salt and distilled, collecting 300mL. This distilllate was then salt saturated again and extracted with 50mL of ether. The ether was removed by simple distillation leaving 1-2mL of crude furfural in the pot, not enough to purify. It gave a strong postive Tollen's test (silver mirror) for aldehyde. It has a subtle and pleasant smell of coffee and almond. If I ever do this again I will use the procedure in OrgSyn, hopefully to get a better yield.

Questions and comments are welcomed.

Paddywhacker - 11-3-2011 at 16:49

That's an interesting comparison with the Orgsyn procedure, Magpie.

The process depends on the dehydration of pentoses, so the the higher the pentose concentration in the raw material the better. Starch and cellulose are hexoses, and don't give any furfural.

So the question becomes "what is the best OTC source of pentoses?"
Bran and corncobs have been used in the past, but is there something better?

DJF90 - 11-3-2011 at 17:21

Xylose, if you can get it. Unfortunately its not a common thing here in the UK...

UnintentionalChaos - 12-3-2011 at 06:37

I had a friend make the brilliant suggestion to use ribose, available as a very questionable bodybuilding upplement, as feedstock. It's another aldopentose and I don't see why it wouldn't work. Not as cheap as bran or corn cob and without the old-timey feel you may be going for, but compact volumes and hopefully higher yield.

[Edited on 3-12-11 by UnintentionalChaos]

Magpie - 12-3-2011 at 09:52

Quote: Originally posted by UnintentionalChaos

I had a friend make the brilliant suggestion to use ribose... It's another aldopentose and I don't see why it wouldn't work.

There are four aldopentoses: arabinose, lyxose, ribose, and xylose. Each has D- and L- configurations.

Are any of these favored in the formation of furfural, aside from availability?

blogfast25 - 15-3-2011 at 14:02

Quote: Originally posted by Magpie

300g of oat bran was used as substrate. This was steeped in dilute sulfuric acid then steam distilled yielding 700mL of distillate. The residue in the pot was char, easily removed. The distillate was neutralized with Na2CO3 then saturated with salt and distilled, collecting 300mL. This distilllate was then salt saturated again and extracted with 50mL of ether. The ether was removed by simple distillation leaving 1-2mL of crude furfural in the pot, not enough to purify. It gave a strong postive Tollen's test (silver mirror) for aldehyde. It has a subtle and pleasant smell of coffee and almond. If I ever do this again I will use the procedure in OrgSyn, hopefully to get a better yield.

Interesting. What were the steeping conditions? Do you simply leave it to stand for some time?

Ribose may (or may not) yield higher yields of furfural but look at these internet prices! Steep (no pun intended)!

[Edited on 15-3-2011 by blogfast25]

Magpie - 15-3-2011 at 14:29

Quote: Originally posted by blogfast25

Interesting. What were the steeping conditions? Do you simply leave it to stand for some time?

Actually, I think "steeping" is not really required here and is my misnomer; it was not called for in the procedure. Steam distillation conditions that are used to separate out the mash are probably all that is required to hydrolyze the pentosans. I let the mix of dilute sulfuric and bran sit overnight merely for my convenience.

I've done some pricing of d-ribose and the best I've seen is about $11/100g. So if you wanted a quantity of furfural that seems like the way to go.

I was surprised how reactive it was in the Tollen's test - put benzaldehyde to shame. No heat was required for either, however.

CORNCOBS r cheap

jimwig - 15-3-2011 at 15:37

CORNCOBS r cheap

UnintentionalChaos - 15-3-2011 at 17:56

Quote: Originally posted by jimwig

CORNCOBS r cheap

Giant bloody flasks and heat sources to hold the volume needed to make comparatively small amounts of furfural with them are not.

[Edited on 3-16-11 by UnintentionalChaos]

blogfast25 - 16-3-2011 at 06:25

Thanks Magpie…

Far more interesting than furfural would be the famous derivatives of THF. I suppose the hydrogenation is outside the capability envelope of most of us here?

The price of Ribose must be somewhat artificially inflated by its primary market. These guys and galls will pay virtually anything!

And how about d-fructose: considerably cheaper than ribose. Wiki:

"DehydrationFructose readily dehydrates to give hydroxymethylfurfural ("HMF"). This process may in the future be part of a low-cost, carbon-neutral system to produce replacements for petrol and diesel from plantations."

Ah... unleaded HMF, super!

[Edited on 16-3-2011 by blogfast25]

Magpie - 16-3-2011 at 09:06

It is interesting that the Gattermann procedure says to expect a yield of 6-7g on 300g of oat bran. This is 0.020-0.023g/g. The OrgSyn procedure, however, says to expect 165-200g/1.5kg of corncobs. This is 0.110-0.133g/g. This a 5-fold yield for the corncobs over the oat bran.

ScienceSquirrel - 16-3-2011 at 09:26

Ribose will form furfural on heating with acid;

http://www.cerlabs.com/experiments/10875404464.pdf

If you wanted a few grams of fufural I think this would be the way to go, 25g of ribose reacting in a 50ml flask to yield maybe 10g grams of furfural sounds way more tempting.

Furfural from Corncobs

gsd - 16-3-2011 at 09:46

A set of 4 articles on this subject appeared in I & EC in 1923-24
by Frederick B. LaForge and Gerald H. Main

I—Factors Influencing the Furfural Yield in the Steam-Digestion Process
II—The Bureau of Chemistry Experimental Plant and Process for Furfural Production
III—Effect of Catalysts on Furfural Yield in the Steam Digestion Process
IV—Economic Aspect of Furfural Production

They are attached below.

Besides this I remember there was an excellent article on comparative study of furfural yields from several pentosan sources such as Oat meal, corn cobs, groundnut husk, rice husk, sugarcane baggase etc. in one old issue of J Chem & Met Engg, which unfortunately is not on the net. I have a photocopy somewhere but it will need lot of digging.

gsd

Attachment: Furfural from Corncobs-I.pdf (158kB)
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Attachment: Furfural from Corncobs-II.pdf (581kB)
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Attachment: Furfural from Corncobs-III.pdf (154kB)
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Attachment: Furfural from Corncobs-IV.pdf (159kB)
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UnintentionalChaos - 16-3-2011 at 11:02

Quote: Originally posted by blogfast25

Thanks Magpie…

Far more interesting than furfural would be the famous derivatives of THF. I suppose the hydrogenation is outside the capability envelope of most of us here?

You never know. Furfural is not a highly aromatic system to the point that strong acid will cleave the ring. It should be much more readily hydrogenated than say, benzene. You probably will not get the aldehyde to a methyl using any easy lab conditions.

IIRC rhodium catalysts can reduce even benzene rings at room temp and 1atm (I may be wrong, don't quote me on it) so they would be great for this.

[Edited on 3-16-11 by UnintentionalChaos]

Magpie - 29-3-2011 at 12:47

For those really into sugar chemistry I see that d-arabinose can be made from calcium gluconate. There is a procedure for this in the forum library that I can't find at the moment. Calcium gluconate is about 1/4 the cost of d-ribose. IIRC arabinose is an aldopentose and should, like ribose, yield furfural upon hydrolysis.

Edit:

Here it is:
http://library.sciencemadness.org/library/books/an_advanced_...

In fact, you can even start with glucose, as the procedures show.

[Edited on 30-3-2011 by Magpie]

[Edited on 30-3-2011 by Magpie]

Magpie - 25-4-2011 at 19:13

Disappointed with the yields of my previous experiments in making furfural, I tried again, this time with fairly good success.

I used a 1/10th scale version of the Org Syn procedure, substituting d-ribose for corn cobs. My pot was a 1000mL RBF with a Hempel column and whatever else I could find to build a long vertical tube. The receiver is a 25mL side-arm test tube. A picture of the assembly is shown below. It uses a Dean Stark mechanism to separate the furfural from the aqueous phase. Density of furfural is 1.159 @13C so it separates nicely from the water. Solubility in water is 9.1g/100, so it is advantageous to use as small a receiver vessel as possible.

I charged the pot with 500mL of 2.17N H2SO4, 200g NaCl, and 32g of food grade d-ribose. This was then set to boiling for 3 hours. As usual the pot contents turned black once boiling temperature was reached. So, all that carbon has to be considered a loss in yield. 8mL, or ~9.3g, of crude furfural was recovered as a translucent yellow liquid. This is a yield of 45.3% based on the d-ribose charged.

Questions, comments, and discussion are welcomed.

ScienceSquirrel - 26-4-2011 at 04:58

I think you might do a little better if you added some salt to the collection vessel. The solubility of organic chemicals in water is affected by the presence of other disssolved materials.
Also extraction with ether would probably get some more of the furfural out of product.
Was there substantial amounts of black material or was it just colouration?
A little black goo goes a long way!

Magpie - 26-4-2011 at 09:47

Quote: Originally posted by ScienceSquirrel

I think you might do a little better if you added some salt to the collection vessel. The solubility of organic chemicals in water is affected by the presence of other disssolved materials.
Also extraction with ether would probably get some more of the furfural out of product.
Was there substantial amounts of black material or was it just colouration?
A little black goo goes a long way!

The small amount of water in the reciver (<20mL) becomes saturated with furfural early in the distillation. From then on the furfural just drops out and settles on the bottom of the test tube. The water in the tube is continually being dribbled back to the pot and refreshed with incoming distillate. I agree that at the end of the distillation I should be able to drive the 8% or so of dissolved furfural out of the water by adding salt.

Yes, ether would be a good solvent but then there is the mess and stink of handling it. On this small scale I don't see it being worth the effort.

As you say, a little black goo goes a long way. I just emptied this flask. Because of the remaining salt it is a little hard to quanitfy the amount of carbon. Several grams is about all I can say.

In August when Mrs Magpie cooks "sweet corn," ie, "corn-on-the-cob," I may give corncobs a try.

GreenD - 26-4-2011 at 12:53

Excuse me, but what is the fuss about furfural?

Are you fellas into biomass and biofuels, or what am I missing here?

ScienceSquirrel - 26-4-2011 at 13:30

I think you are right and there is little more to be gained.
It is a complex condensation reaction and the chance of any one molecule of ribose twisting around to the right conformation, eliminating and condensing in the right reaction order to make furfural or making goo may have a statistical limit.

watson.fawkes - 26-4-2011 at 13:54

Quote: Originally posted by GreenD

Excuse me, but what is the fuss about furfural?

It's feedstock into furan, and from there to tetrahydrofuran (THF) and others.

Magpie - 26-4-2011 at 14:24

Quote: Originally posted by ScienceSquirrel

...
It is a complex condensation reaction and the chance of any one molecule of ribose twisting around to the right conformation, eliminating and condensing in the right reaction order to make furfural or making goo may have a statistical limit.

That is an interesting way to look at it. Indeed, each ribose molecule must lose 3 molecules of water to form furfural. I too was wondering why so much of the ribose ends up as carbon. At first I was using a much stronger acid, even sulfuric, which is known for its tendency to carbonize. But this last batch was only 2.17N in H2SO4, or HCl, however you want to look at it. OrgSyn, however claims a very high yield when using corncobs. We'll see how I do with those in August.

@GreenD: I'm making furfural just for the heck of it. It's an interesting looking aldehyde, and being able to make it from corncobs, straw, oat hulls, etc, just adds to the intrigue.

Arthur Dent - 27-4-2011 at 04:03

@ Magpie: Quick question, what do you do to the corn cobs to prepare them into a primordial soup? Just dilute sulfuric acid? How long does it take to boil off? Corn cobs are pretty sturdy things, so I figure it might be a long process to digest those...

- Robert

Magpie - 27-4-2011 at 07:45

Robert, here's the procedure as found in OrgSyn. For those who don't know, this cornocopia (no pun intended) is freely available to the public.

http://www.orgsyn.org/orgsyn/default.asp?formgroup=basenpe_f...

Yes, the cobs apparently can take 5-10 hrs to digest.

blogfast25 - 27-4-2011 at 07:49

A very interesting experiment, Magpie, look forward to the details on the corn-on-the-cob run.

If only there was an easy way to convert to THF. Or is there?

How much did the ribose set you back?

Magpie - 27-4-2011 at 08:12

Quote: Originally posted by blogfast25

How much did the ribose set you back?

I paid $20/100g at my local health food store. I've seen it on the internet as cheap as $11/100g.

---------------------------------------------------------------------
According to OrgSyn furan can be made easily by the decarboxylation of 2-furoic acid. OrgSyn also shows how to make this acid from furfural. It looks simple enough.

[Edited on 27-4-2011 by Magpie]

blogfast25 - 27-4-2011 at 11:57

Wow. $110/kg. Cheap it ain't!

aliced25 - 2-6-2011 at 19:02

Here's a few papers on the production of furfural from pentoses. They cover producing useful pentoses from the oxidation of hexoses and the formation of furfuryl from pentoses (the biphasic systems look awfully promising).

Attachment: Fullmer.etal.The.Production.of.Furfural.from.Xylose.Solutions.by.Means.of.Hydrochloric.Acid.Sodium.Solutions.pdf (488kB)
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Attachment: Heines.Microdetermination.of.Pentoses.by.the.Bisulphite.Method.pdf (81kB)
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Attachment: Hockett.Hudson.Improvements.in.the.Preparation.of.d.Arabinose.from.Calcium.Gluconate.pdf (246kB)
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Attachment: Hudson.Harding.The.Preparation.of.Xylose.from.Corn.Cobs.pdf (151kB)
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Attachment: Hurd.Isenhour.Pentose.Reactions.I.Furfural.Formation.pdf (881kB)
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Attachment: Isbell.Holt.Frush.Preparation.of.D.Arabinose.5C14.from.D.Glucose.6C14.pdf (61kB)
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Attachment: Matsushima.D.Arabinose.Hypochlorite.Glucosamine.pdf (258kB)
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Attachment: Weingarten.Kinetics.of.Furfural.Productioni.by.Dehydration.of.Xylose.in.a.Biphasic.Reactor.with.MW.Heating.pdf (348kB)
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asilentbob - 8-6-2011 at 22:46

Xylitol is readily available OTC from health stores, grocery stores, etc as a sugar substitute... I have wondered if it could participate similarly to xylose, except losing 4 moles water per mole of xylitol, instead of 3.

Its been entirely too long since I took Ochem.

Magpie - 13-8-2011 at 16:19

I have been drying some corncobs for making furfural per the method in OrgSyn. I'm getting them as they are received from the dinner table. I crushed 4 of them up yielding 114.4g for a 0.076 scale batch.

Dried corn cobs are a bitch to granulate. I eventually settled on using a pair of channel locks but it still took me 2 hours of tough going. The kernel hulls are fragile but the center core is very tough, much like wood. If I ever do this again I will try making them into sawdust using my table saw.

I made up enough H2SO4/NaCl solution for a 0.10 scale batch and since the cob granule slurry looked too dry I added it all. Tomorrow I will set up for steam distillation using a 1000mL RBF, column, and Dean Stark trap, as before.

Here's some pictures:

blogfast25 - 14-8-2011 at 05:26

Someone should contemplate recycling these things into baseball or cricket bats...

Look forward to reading about the rest of this synthesis!

Ozone - 14-8-2011 at 09:49

Many seed hulls, particularly those from sunflower seeds, are especially rich in hemicellulose (primarily arabinoxylan with almost no cellulose). I expect these to be excellent feedstock for a process like this. I might give it a shot after I get a kg or two of seed hulls.

Cheers,

O3

Magpie - 14-8-2011 at 20:57

Quote: Originally posted by Ozone

... sunflower seeds, are especially rich in hemicellulose (primarily arabinoxylan with almost no cellulose). I expect these to be excellent feedstock for a process like this.

If this converts to arabinose it indeed ought to be a good feedstock & interesting to compare to the oat bran, corn cobs, and d-ribose that I have used.

The steam distillation of the corncob hydrolysis was completed today. I ran it for 4 hours but it was pretty much finished after 3 hours. OrgSyn's preparation says it will take 5-10 hours for their 1.5kg batch.

My yield was 7.5g. Scaled on OrgSyn's expected yield I should have obtained ~15.2 g. But my vastly smaller scale (0.076X) is likely a major factor in my smaller yield.

Again the mash turned black after it started boiling. Pictures are shown below.

This completes my investigation of natural products for the preparation of furfural. If I want any more I'll use d-ribose as available from my neighborhood health food store.

[Edited on 15-8-2011 by Magpie]

Magpie - 2-9-2011 at 14:17

Wanting to do some chemistry this week, but nothing too challenging, I decided to purify my crude furfural and then make a derivative of same.

I took the combined lots of furfural that I had made from the various sugar and pentosans, which amounted to about 25mL of straw colored translucent liquid, and vacuum distilled it. Pressure was 50mmHg using an aspirator with the resulting bp at 76C. Being a bit lazy I did not at first set up an ebulliator and a Claisen extension. This proved to be a big mistake due to bumping and carryover so shutdown and reconfigured the right way. Yield was 20mL of clear product with a pleasant aroma - I would call it that of "benzaldehyde light."

Using 1g of homemade semicarbazide, some Na acetate buffer, and 1.5mL of furfural I made the derivative furfural semicarbazone (an imine) according to the method in Brewster. This crystallized out without any help from scratching or cooling. I recrystallized it from 95% ethanol, washing it with same. A melting point was taken of the dried crystals (see picture); it melted at the literature (Wiki) value of 202C.

I find it interesting that furfural is aromatic. Also it is interesting that the terminal nitrogen of the semicarbazide is the only one (of 3) capable of nucleophillic attack due to resonance.

[Edited on 2-9-2011 by Magpie]

Random - 2-9-2011 at 21:47

Well, I tried dry distillation of sucrose before, until it carbonized. I obtained very small amount of liquid with the color just like this crude furfural you made, though it had some oily caramel colored dot floating on that yellow liquid. The liquid smelled like burning sugar and caramel (and I wonder why

). My distillation apparatus was made from aluminium foil so it was really bad one, a lot of fumes escaped. Maybe that liquid contained furfural too?

Nicodem - 3-9-2011 at 12:13

Good work Magpie!

Quote: Originally posted by Magpie

I find it interesting that furfural is aromatic.

Aromatic, but not much. If you think furane is much of an aromatic system, then you might be surprised at how easy it undergoes nucleophilic additions. Particularly the reactions with amines and anilines are interesting as they give the corresponding pyrrole compounds from the furanes. For example, furfural itself reacts with anilines such as p-nitroaniline to give 1-(4-nitrophenyl)-1H-pyrrole-2-carbaldehyde. This is a nice looking heterocyclic product which can be further functionalized at the aldehyde group. References:

See DOI: 10.1071/CH9850953

Also, from CA 92:180923

Quote:

Synthesis of 1-arylpyrrole-2-aldehydes from furfural and substituted aromatic amines.
Burmistrov, S. I.; Sannikova, V. M.
Voprosy Khimii i Khimicheskoi Tekhnologii (1979), 54 20-4.

Abstract: Pyrrolecarboxaldehydes I (R = 4-H2NSO2C6H4, Q, 4-nitro-1-naphthyl, 2,5- and 2,4-HO(O2N)C6H3, 2,3,5-HO(Cl)(O2N)C6H2) were prepd. in 23.2-87.6% yield by reaction of furfural with the resp. arom. amine. The semicarbazones, phenylhydrazones, 4-nitrophenylhydrazones, 2,4-dinitrophenylhydrazones, and azines of some I were also prepd.

...and from CA 95:203666

Quote:

Synthesis of 1-(4-nitrophenyl)pyrrole-2-aldehyde from furfural.
Baum, E.; Goldovskaya, T. E.; Kul'nevich, V. G.; Maiorova, O. V.
Khimiya Geterotsiklicheskikh Soedinenii (1981), (8), 1062-6.

Abstract: The condensation of furfural with p-O2NC6H4NH2 in different solvents (e.g., MeOH, EtOH, PrOH, DMF, or HOAc) contg. HCl gave 55% pyrrolealdehyde I and 27% 2,3-bis[(4-nitrophenyl)amino]-4-cyclopentenone. Yields of up to 70% were obtained using methods described earlier (e.g., Liipke, 1939).

...and briefly described in DOI: 10.1007/BF01042479

aliced25 - 3-9-2011 at 15:16

Bagasse is going to be far easier to work with than corn cobs (given it is already shredded and readily available in most garden stores - it is used as mulch). Rice husk is another easily (and cheaply) acquired source of xylose, there is a paper (here) on the extraction of xylose from Rice Husk/Hulls using 1N H2SO4. Making furfural from the sugar is going to be way easier given the lack of bulk and the reduction in the amount of acid needed.

Magpie - 3-9-2011 at 17:48

I agree that it is good to reduce the bulk of the precursor as much as possible. Although expensive, I did this using OTC d-ribose. However, even using this pure sugar the best yield I could get was 45%. When I tried it again I got exactly the same yield. A great deal of the precursor is just turned to carbon.

Ozone - 4-9-2011 at 07:41

Just some notes on your alternative feedstocks:

Yes, but bagasse contains 50% w/w water and 2-4% residual cane juice; it is only 20-24% hemicellulose (most of which is arabinoxylan). It is also recalcitrant. I would go for cellulosic ethanol then concentrate and work on the stillage (which contains all sorts of interesting things like aconitic acid, your xylan, etc.)

NIST sugarcane bagasse (from my lab % w/w dry solids):

extractables: 4.4
Cellulose: 40.2
Hemicellulose: Xylan 21.8, Arabinan 1.8 and mannan 0.4
Lignin: Klason 22.3, AS 2.0
Ash: 4.0

Rice hulls come nice and dry, which is a plus for storage and compositionally simple. But, again, these are a rich cellulose source with a composition (La. rice hulls, results from my lab) similar to:

extractables: 2.2
Cellulose: 33.0
Hemicellulose: Xylan 15.8, Arabinan 1.3 and mannan 0.0
Lignin: Klason 24.0, AS 2.7
Ash: 19.0

It should be mentioned that rice hulls are flame retardant (I had a hard time getting them to combust in a Parr bomb under 19 atm O2) and that the huge amount of ash is part of the plant structure; it is at least 94 % silica.

Cheers,

O3

[Edited on 4-9-2011 by Ozone]

blogfast25 - 5-9-2011 at 07:38

Very interesting data, O3. Also that point on > 94 % silica in ash, I wonder how that compares to most plant ashes...

Ozone - 5-9-2011 at 20:13

Yes, I thought so, too. When totally combusted to ash, you get a *fine* pure-white silica. I have thought about trying it out (as a stationary phase) in a column.

It would be cool if we could source relatively high-grade silica from rice hulls.

Cheers,

O3

watson.fawkes - 7-9-2011 at 04:00

Quote: Originally posted by Ozone

It would be cool if we could source relatively high-grade silica from rice hulls.

Certain species of horsetail are known as "scouring rushes" because of the high content of silicates; they're a naturally occurring plant abrasive. I would be curious to know what happens when you ash these, but not curious enough to acquire the gear just for this one experiment.

aliced25 - 12-3-2012 at 01:38

Here is some more - interestingly enough HCl or H3PO4 are the acids of choice for this procedure - with steam distillation being the preferred way of isolating the product from the 'strong' acid before it degrades too much (I suspect your choice of acid would be responsible for much of the charring).

What would be nice is a decent, completely otc route to THF, pyrrole, porphyrins, etc.

[Edited on 12-3-2012 by aliced25]

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niertap - 14-3-2012 at 21:19

Fructose will give one of the best yields. Acid catalyzed hydrolysis of sucrose should give a good supply of it. I don't really think anyone knows why frustose will give a 75% yield or something like that.

You may have to add a little silica jell, though. It seems to facilitate reactions with diols or more ols. When put through GCMS the polyols will kind of rip little bits of the column out.

however if you put any fructose containing mixture(ex. fruit juice) through it, the fructose will read as furfural.

I believe some organization was trying to find a great way to make it for use as an alternative fuel source. Fructose all the way.

Fructose

all the way

bbartlog - 15-3-2012 at 03:21

Quote:

Acid catalyzed hydrolysis of sucrose should give a good supply of it.

Under what conditions, using what acid? One possible outcome of such hydrolysis is levulinic and formic acids (and plenty of black gunk in an insoluble cake), per Organic Syntheses: http://www.orgsyn.org/orgsyn/prep.asp?prep=CV1P0335
Now maybe with less water, or a dehydrating acid (such as sulfuric acid), or other conditions... do you have a reference?

Boffis - 31-12-2020 at 05:42

This is a long dormant thread but I think it is worth reviving. Over the last few years, each spring, a flowering cherry tree in our garden weeps a clear liquid that quickly turns rubbery and finally turns into a hard glassy gum. The soft material swells in water but once hard it is surprisingly resistant to cold water. Some digging around on the internet shows that this type of gum is rich in pentose sugars. I initially tried to extract the arabinose but it is very difficult to isolate it as a crystalline solid so I decided to see if I could recover any furfural from it by distillation with acid. The result was 5.5g of pale straw coloured furfural from 58g of gum. I suspect a better yield could be obtained directly from the gum but I did a lot of acid hydrolysis and processing on the material before I tried to recover the furfural. I estimate that the final syrup contained about 38g of solids. I will try again if we get another crop this coming spring.

After this modest success I tried the same process on 25g of xylose and then the same weight of ribose. With xylose I got about 8.9g which is about 55% yield and with D-ribose I got 63% yield. Looking at the literature these are good yields.

I am currently investigating the possibility of using other sources such a sodium gluconate which can be oxidized to arabinose with H2O2 and hypochlorite oxidation of glucosamine which also yields arabinose.

I am in the process of writing a detailed article for the prebulication section; maybe get it out today.

DraconicAcid - 31-12-2020 at 12:00

Nice! (Now oxidize it to an acid and make some esters!)

Boffis - 31-12-2020 at 12:31

Ethyl furoate, what does that smell like

DraconicAcid - 31-12-2020 at 12:38

Only one way to find out.....

Fery - 31-12-2020 at 21:56

Definitely worth trying it! I do not know why the same substance has 2 different CAS numbers and contradictory scent information:

http://www.thegoodscentscompany.com/data/rw1433881.html
Name: ethyl furan-2-carboxylate
CAS Number: 1335-40-6
Recommendation for ethyl furoate usage levels up to: not for fragrance use
Melting Point: 33.00 to 36.00 °C. @ 760.00 mm Hg
Boiling Point: 196.00 °C. @ 760.00 mm Hg

http://www.thegoodscentscompany.com/data/rw1022631.html
Name: ethyl furan-2-carboxylate
CAS Number: 614-99-3
Odor Type: balsamic fruity floral orchid
Melting Point: 35.00 to 37.00 °C. @ 760.00 mm Hg
Boiling Point: 196.00 °C. @ 760.00 mm Hg

Sigma-Aldrich catalogue uses only the second CAS number and the first one is not present there.

Fery - 31-12-2020 at 23:39

Boffis thx for reviving this thread. I have hundreds of wild cherry trees in my forest (yet small, I planted them there only 10 years ago). I grow sweet corn every year in my garden and there are plenty of huge agricultural fields with common corn around (to feed cattle with fermented plants = silage during winter) - no problem with corncobs.
I've bought d-ribose 100 g for 119 CZK which is 4,5 EUR... I guess it was sale-out of pharma grade compound near to its expiration date as it is not available there anymore and strange low price:
https://fichema.cz/241-d-riboza
When I find something very cheap I just buy it for possible future use even without actual ideas what to do with it. Now I know

Boffis - 1-1-2021 at 03:28

Hi Fery, I hope to get my prepub posting up today. But yes the price of D-ribose in the UK now is as low as £25 per Kg (about 29 euros), xylose was even cheaper but the company that sold it has disappeared. Prunus sps. gums look like an ideal source for small scale production though if you have a ready source. If you do try it let us know how you get on using it as a source directly.

Another possible source that has just occurred to me is xylitol. I don't think this pentol will give furfural directly but I was wondering if it can be oxidised to a pentose with say hypochlorite or H2O2/Fe. There would be no need to isolate the sugar. I may try this as xylitol is cheap in our local supermarket.

[Edited on 1-1-2021 by Boffis]

Fery - 1-1-2021 at 10:53

Hi Boffis, good and cheap source!
xylitol costs here cca 10 EUR per 1 kg pharma/food grade
https://fichema.cz/265-xylitol-brezovy-cukr

I found an information about methyl furoate:
https://sci-hub.st/10.1002/14356007.t11_t02
methyl 2-furoate [611-13-2]: fruity, mushroom-like odor

and the furfural = 2-furaldehyde [98-01-1]: freshly baked bread odor
wow! I love bread, it is substantial portion of my food! Looking forward the synthesis...

valeg96 - 1-1-2021 at 11:23

Fichem.cz only ships and sells within CZ and SK. Sad, because they have some really good chemicals and prices.

Boffis - 2-1-2021 at 01:15

OK I've posted my full write-up on the preparation of furfural from various source over in the "Prepublication" section.

Yesterday I also ran a larger scale preparation from xylose using 150g with 440g of salt in 1.5 litres of solution and over 7 hours recovered 51.5g of crude furfural which is about 53.5% so almost exactly the same recovery as before in spite of the increased ratio of salt to xylose and the larger scale.

Anyone any ideas on the oxidation of xylitol to a pentose?

Boffis - 4-1-2021 at 01:53

I have now repeated the larger scale preparation using 150g of D-ribose in stead of xylose. I used exactly the same procedure as above but the yield was only 25.2g and no further furfural passed over after 3 hours. It seems that ribose is not a good source for large scale furfural preparations by this route.

Fery - 4-1-2021 at 04:10

Hi Boffis, you used 25 g ribose in your first synthesis which yielded 10,2g of fural and now 150g of ribose which is 6x more and yield 25,2g. Did the distillation last the same time in both preparations? If this second synthesis lasted approx 2x longer (because of bigger flask) then perhaps it is a hint that fural has to be distilled out of the reaction mixture as quickly as possible... just guessing... if this is true then even returning water saturated with fural back into the distillation flask is contraproductive, perhaps collecting distilled water with fural and then put this into dean stark trap apparatus with a hope that without acid the fural won't decompose on the second distillation? During the reaction instead of returning water saturated with fural from the condensate back into the distillation flask just dripping there clear water from dropping funnel as a lazy solution or steam as an advanced solution?

Boffis - 4-1-2021 at 10:41

Hi Fery, Yes. In both cases with xylose I had to run the reaction for about 7 hours to get to a point where no more furfural droplets formed. I have discovered that it is important to keep the reflux rate as low as possible. I think that this is because furfural is slightly soluble in warm water and the higher the reflux rates it is simply carried back into the boiling flask. I have thought about using external steam injection (ie true steam distillation) to increase the rate of extraction but this then gets back to the old problem of recovering the furfural from a large volume of aqueous distillate. The replenishment of the water with fresh water and collecting all of the distillate clearly has the same problem.

With ribose at the 25g scale distillation lasted 5 hours but at the 150g scale distillation was over in only 3 hours and the yield was lower (26 as against 60+%). The problem may be that as U235 commented, ribose reacts more quickly and can't be removed fast enough so ends up being decomposed. Reducing the reflux rate makes this worse but conversely increasing the reflux rate simply returns more to the reaction flask and hence decomposition.

I am currently setting up an experiment to carry out tomorrow using 100g of very strong ribose solution and add it slowly to boiling salt and acid. I'll let you know how I get on

.

One final thought. Does anyone know of a use for the black humic material?

[Edited on 4-1-2021 by Boffis]

Boffis - 11-1-2021 at 15:11

While emptying out the flask from one of the reaction I found these beautiful hopper salt crystals in the black residue. They are about 9mm on edge, there were larger ones but they were not so cute.

[Edited on 11-1-2021 by Boffis]

Boffis - 16-1-2021 at 13:02

I have now run two attempts at Fenton oxidation of xylitol (Fe2+ catalyzed H2O2 oxidation) and then distilled the product without isolation of the xylose. The first experiment used a 1:1 Molar ratio of xylitol to H2O2 and 50g of xylitol gave just 3.37g, I was expecting 15-18g. The next run I used a ration of 1:2 but the yield fell to zero.

I then tried Fe3+ catalyzed H2O2 oxidation of sodium gluconate to arabinose followed by acidification and distillation; again the yield was practically zero. (aniline test was strongly positive on the aqueous distillate but no oil separated).

Then I tried oxidising glucosamine HCl with hypochlorite solution to give arabinose and then distill this with salt and HCl. Again the yield was zero though the aqueous phase gave a positive test for furfural.

I am currently following a published procedure to oxidize 187g of sodium gluconate to the letter and then intend to isolate the arabinose as a solid. I will try then to distill this material.

At present it still looks like d-ribose, available in the UK for 3 to 4 pounds sterling per 100g which gives about 30-35g of furfural if distilled in small batches is the best amateur route. Xylose is a better source on a larger scale because its cheaper but it is less readily available OTC.

Fery - 15-3-2021 at 10:12

Quote: Originally posted by Boffis

Ethyl furoate, what does that smell like

Hi Boffis, I've bought something else but from this family - furfuryl acetate, the ester of furfuryl alcohol and acetic acid.

From here:
https://shop.es-drei.de/ester/694/essigsaeurefurfurylester-m...

here info about its scent:
http://www.thegoodscentscompany.com/data/rw1017931.html
sweet fruity banana horseradish

For me it scents like horseradish, but the scent is not unpleasant, I would rather say neutral. I do not recognize sweet / fruity / banana in it. I was unable to identify the scent for the first time, I only remembered that I already scented it sometimes. Only after reading the scent description I suddenly remembered. My father grated horseradish from his garden a lot of times, it was especially served with ham and meat around Easter. I'm growing horseradish in my garden too since previous year, but I did not yet dug its roots out of the soil, maybe I'll try in few weeks. Strange that I remembered the scent but was unable to assign the source from which I knew it. And only after reading info I remembered. We have memory for images, sounds, touches (body map + type of sensation like touch/cold/warm/pain/vibration etc), tastes and scents.

Boffis - 17-3-2021 at 03:26

Mmmm I'm trying to imagine the smell of horseradish. I don't find it has a smell as much as a mustard like sensation in the nose!

I am preparing bromine at present to prepare some mucobromic acid from my furfural. I now have about 300ml so I should have plenty left (I'm going to use the Org. Synth. route half scale.). One of the things I might try is the oxidation to furoic acid. I have already prepared furoin and furil and posted the preparation of them somewhere on SM; so ethyl furoate shoul;d be a possibility.

Fery - 17-3-2021 at 07:05

Hi Boffis, grated horseradish has quite unpleasant effect in copious secretion from nose and flood of tears. Furylacetate has only the scent without the lachrymator allyl isothiocyanate present in horseradish. When you buy ready to eat grated horseradish in a jar, it is too weak, but when you try to grate fresh root, its power is demonstrated meters faraway.
When you have 2-furaldehyde, Cannizzaro reaction produces alcohol + acid, you can separate 2-furfurylalcohol by extraction into organic solvent while 2-furoic acid stays in water phase in a form of Na salt. But that you know much better than me, you already posted nice Cannizzaro reaction experiment.

Boffis - 17-3-2021 at 12:02

I have thought about Cannizzaro's reaction but its not very efficient with furfural because furfurol tends to resinify. Since I am more interested in the acid I may try oxidation of furfural.

zed - 17-3-2021 at 15:28

Good prices on sugars. Nice clean starting material. Me? I'm in the land of "Corn on the Cob". At the right 4th of July picnic, I could salvage maybe 50 gallons of Corn Cobs. According to Org. Syn., that's a lot of Furfural.

Cannizaro is a good start. 50% yield of the acid, right from the get go. Then, you can oxidize the Alcohol to the Acid. Though, as the Wicked Witch Said: "These things must be done delicately" "So as to not spoil the magic!"

Conjugated system. And, the problem with oxidizing agents, is reining them in. Need to be wary of those double bonds.

I'm gonna go back and study this whole thread.

[Edited on 17-3-2021 by zed]

[Edited on 17-3-2021 by zed]

Texium - 17-3-2021 at 16:52

Marginally related: here’s an old paper on the preparation of furfuryl furoate.

Attachment: ja01682a035.pdf (150kB)
This file has been downloaded 294 times

zed - 17-3-2021 at 19:00

Well, I checked back a decade or so, and this is an old thread.

It no longer seems to contain an active link to this Corn Cob procedure.

Said procedure, containing pointers on how gently you've got to handle Furfural.

It seems to "remember" abuse, and avenge itself later.

http://www.orgsyn.org/demo.aspx?prep=CV1P0280

http://www.orgsyn.org/demo.aspx?prep=CV1P0276

[Edited on 18-3-2021 by zed]

clearly_not_atara - 12-9-2024 at 18:59

Quote: Originally posted by Boffis

At present it still looks like d-ribose, available in the UK for 3 to 4 pounds sterling per 100g which gives about 30-35g of furfural if distilled in small batches is the best amateur route. Xylose is a better source on a larger scale because its cheaper but it is less readily available OTC.

I believed this too, until about five minutes ago. It is certainly true that xylose is not sold at the grocer. But it turns out that polymers of xylose are not nearly as rare. The popular supplement psyllium (Metamucil) consists primarily of arabinoxylans (60% w/w), polymers of primarily xylose with some arabinose, these both being pentoses. And here we are as OTC as it gets! Available in the UK from at least one retailer for £21/kg and cheaper in the US.

EDIT: Furfural is effectively oxidized by oxygen in the presence of a copper manganate (CuMn2O5) and NaOH:

https://www.sciencedirect.com/science/article/pii/S246802572...

Rxn conditions were 120 C, 1 Mpa O2 with a low catalyst loading (0.05 wt% of furfural) but a higher catalyst loading and a longer rxn time could allow avoiding the autoclave. Nonetheless, the pressure and temperature were relatively mild for an aerobic oxidation.

In theory the inclusion of stoichiometric MnO2 with a Canizzarro drives the rxn to the right:

2RCHO >> RCH2OH + RCO2H

RCH2OH + MnO2 >> RCHO + Mn2O3

This likely explains the rxn above, with Cu as an oxygen activator as it is also used in the Wacker process.

The catalyst is prepared by the thermal decomposition of copper (II) permanganate, which is achieved by autoclaving a solution in the paper, but might be effectively replaced by isolating the salt.

[Edited on 13-9-2024 by clearly_not_atara]

Boffis - 14-9-2024 at 13:12

Hi clearly_not_atara; this is an interesting find psyllium ground seeds are as you say readily available. I am coming back to my work on furfural, I have been somewhat distracted by other things. So I will probably give it a go in the near future. Have you tried working with this stuff? I can imagine that it will form a gloopy mess to start with. Do you think it would be best to hydrolyse it first with say 1-2% acid first and then add more HCl and salt for the dehydration of the pentoses?

I wonder if you could isolate the xylose and arabinose from the hydrolysate?

Added comment: have just spotted xylose on ebay for under £9 per kg, less than I can buy psyllium for!

[Edited on 15-9-2024 by Boffis]

clearly_not_atara - 16-9-2024 at 09:50

Quote: Originally posted by Boffis

Hi clearly_not_atara; this is an interesting find psyllium ground seeds are as you say readily available. I am coming back to my work on furfural, I have been somewhat distracted by other things. So I will probably give it a go in the near future. Have you tried working with this stuff? I can imagine that it will form a gloopy mess to start with. Do you think it would be best to hydrolyse it first with say 1-2% acid first and then add more HCl and salt for the dehydration of the pentoses?

No experience with psyllium, as I said, I posted about it as soon as I found out. I agree it would probably be gloopy. That is its, er, intended function

Hydrolysing it first seems like it could help, but it should also hydrolyse in situ. The disadvantage would be in going from the dilute acid to the strong acid: you either have to add a huge amount of azeotropic HCl, use fuming HCl, or use HCl gas. Neither possibility seems attractive.

Nice find on the xylose. Who would have thought?