Klute
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Rongalite (Sodium Formaldehyde Sulfoxylate) preparation
Is anyone familar with this coumpound? Apparently it is made by reacting formaldehyde with sodium dithionite:
Na2S2O4 + 2 CH2O + H2O --> NaHOCH2SO3 + NaHOCH2SO2
Apparently, the reaction quantitative , so this a way of titrating dithionite (wikipedia). I haven't found much on it's manufacture though. I'm
asking myself how it could be seperayed from the sodium formaldehyde sulfonate (?).
Apparently it decomposes at 80°C, emmiting H2S, formates, sulfites and methanol
http://www.ramkishore.com/rongalite.htm
I was thinking of mixing dithionite with 30% formaldehyde, evaporating part of the water under vacuum, and crashing the salt out with, say ethanol
(i guess acetone would be reduced). Apparently this paper reduces diselenides with SFS in aq ethanolic solution, so i can't be sure how soluble it is in ethanol (page 6,
bis(phenylseleno)methane 7a).
Also, i can't find any solubility data on the sulfonic salt, so i don't know how to seperate both.
I plan on using this reducing agent to reduce disulfides to thiophenols insitu. Apparently this can be done with dithionite or thiosulfates, albeit
in lower yields. And i don't want to purchase the minimum 250g for only small scale reactions, i prefer trying to make it out of cheapish dithionite.
Any advice or comments are welcome.
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smuv
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This may help. From Merk Index 14th ed.
Monograph Number: 0008620
Title: Sodium Formaldehydesulfoxylate
CAS Registry Number: 149-44-0
CAS Name: Hydroxymethanesulfinic acid sodium salt
Additional Names: formaldehyde sodium sulfoxylate; formaldehydesulfoxylic acid sodium salt; sodium hydroxymethanesulfinate;
sodium methanalsulfoxylate
Trademarks: Aldanil; Rongalite; Rongalite C
Molecular Formula: CH3NaO3S
Molecular Weight: 118.09
Percent Composition: C 10.17%, H 2.56%, Na 19.47%, O 40.65%, S 27.15%
Line Formula: Na[HOCH2SO2]
Literature References: Prepn: Heyl, Greer, Am. J. Pharm. 94, 80 (1922); Binns, US 2013125 (1935 to Virginia Smelting); Postnikov,
Kunin, J. Appl. Chem. USSR 13, 185 (1940). Structure of dihydrate: Truter, J. Chem. Soc. 1955, 3064; 1962, 3400. Of limited value in treatment of
mercuric chloride poisoning: Modell et al., J. Pharmacol. Exp. Ther. 61, 66 (1937).
Derivative Type: Dihydrate
Properties: Crystals, mp 63-64°, dec at higher temp. Odorless when freshly prepd, but quickly develops a characteristic (garlic)
odor. Freely sol in water; practically insol in abs alcohol, ether, benzene. Readily dec by dil acids. Aq soln is practically neutral. Keep well
closed in a cool place. LD s.c. in mice, 4.0 g/kg: Rosenthal, Public Health Rep. 49, 908 (1934).
Melting point: mp 63-64°
Toxicity data: LD s.c. in mice, 4.0 g/kg: Rosenthal, Public Health Rep. 49, 908 (1934)
Use: In vat color printing pastes: Borstelmann, Fordemwalt, US 2597281 (1952 to Am. Cyanamid). In polymerization of ethylenic
compds: GB 816252; GB 852593 (1959 to Hercules Powder; 1960 to Air Reduction). In manuf of arsphenamines: Krumwiede, J. Am. Pharm. Assoc. 8, 795
(1919); Heyl, Miller, ibid. 11, 432 (1922).
Therap-Cat: Treatment of mercury poisoning.
EDIT: Judging by the above US patent and what was written in the mentioned J. Chem. Soc. articles, Rongalite is most commonly perepared from
dithionite generated in situ from zinc dust and a source of sulfite. The only useful portion of J. Chem soc. 1965, p.3043, was 'When a mixture of
sodium hydrogen sulphite and formaldehyde is reduced by zinc dust in alkaline aqueous solution, a strongly reducing compound can be salted out. This
compound is generally known as " Rongalite C " or " Formosul,"'
[Edited on 29-3-2008 by smuv]
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Klute
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Thanks alot for your help.
The problem is that i wanted to use Rongalite to avoid using Zn powder in the first place, even though it (Rongalite) can lead to a one pot reaction
(disulfide-->thiophenol-->thiolate-->thioether) when adding rongalite to a mixture of disulfide, alkyl halide and K2CO3 in DMF, avoiding the
usual stench of thiophenols. I want to try a similar scheme for the formylation of thiophenols, generating it just before the reaction, in a closed
system. If i directly use Zn/HCl, i have to isolate the thiophenol before either alkylating it or formylating it.
I will have to compare the amount of Zn used, i really would be pissed to buy 250g when i only need 10-20g.
I guess that during the reduction, the sulfite is reduced to dithionite, which combines with formaldehyde according to the reaction above, and that
the sulfonate genetated is either reduced directlyt, or dissociates to sulfite and formaldehyde, and the cycle starts again. I don't understand how
the formaldehyde could stand the Zn without being reduced to methanol though.
Thanks again Smuv
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smuv
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I'm just thinking out loud. Maybe the formaldehyde is protected by the bisulfite adduct, or maybe it is reduced to some extent, but it really doesn't
matter as methanol is easy to separate from the product.
Regarding your wishes to avoid the zinc reduction, you could try making Rongalite from sodium dithionite and formaldehyde and try to purify it via
crystallization (although I can't find much solubility data about either rongalite or the formaldehyde bisulfite adduct). On the other hand you could
just try your target reaction with the formaldehyde bisulfite impurity, as I am pretty sure that the bisulfite adduct is either a product or
intermediate of any rongalite reduction.
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Klute
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After several hours of searching, i have found little information.
This article suggests that any aldehyde react with dithionite to form sulfoxylates. GarageChemist has kindly accepted translating the refrenced
procedure under 22 a and b.
Now it's unclear if 2 mols of aldehyde reacts with one mole of dithionite and gives 2 moles of sulfoxylate, or if only one mol of sulfoxylate is
formed, accoring to the reaction i posted above. We will see what the article says. Even if the reaction doesn't produce equimolar amounts of
bisulfite adduct, some amount should be formed from the side reaction:
S2O42- + H2O --> SO2 2- + HSO3 2-
Maybe both can de effectively seperated by recristallization, or perhaps stirring in a somewhat basic medium could reverse the bisulfite-adduct
formation, the rongalite is said to be stable at relatively high pH. K2CO3 is used in the procedure i plan on using, so residual carbonate won't be a
problem.
I plan on using it for the direct synthesis of thioethers from disulfides with alkyl halides. Although sodium dithionite is said to work albeit in
lower yields (40-60%), the formation of the disulfide is already pretty low-yielding (40-50%) so i want to maximise yields on that reaction.
[Edited on 30-3-2008 by Klute]
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Klute
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Here is the translation very generously done by GarageChemist of the first article mentionned above, dealing with preparation of Rongalite. Thanks
alot GC, i would have been clueless on the way of isolating this salt without your help!
| Quote: | Translation of the german article by GarageChemist
I acquired both references.
The first one contains a simple preparation of formaldehyde sulfoxylate, the second one only of benzaldehyde sulfoxylate.
You only want the preparation of formaldehyde sulfoxylate, right?
So here's an english version of the relevant parts:
There are previous claims to the action of formaldehyde upon hydrosulfurous acid in the english patent 5867 1903. It claims the action of formaldehyde
upon sodium hydrosulfite in neutral and acidic solution in order to achieve a preservation of the hydrosulfites for etching purposes. It has been said
that such a preservation occurs when sodium hydrosulfite (= dithionite, I think) with such an amount of formaldehyde as can be bound. The claimed
product has the formula 2 CH2O*Na2S2O4, crystal water disregarded.
I (meaning the author of the german paper) have now found that a very different reaction occurs when 1 mol formaldehyde acts upon 1 mol hydrosulfite
in the presence of NaOH.
If 1 mol sodium hydrosulfite-solution is shaken with 1 mol NaOH-solution and 1 mol formaldehyde, an exothermic reaction occurs, and the reduction
potential of the solution towards indigo carmine solution in the cold disappears after some time.
If this solution is now mixed with an equal volume of alcohol under cooling, neutral sodium sulfite precipitates.
The alcoholic solution gives a syrup upon evaporation in vacuum which solidifies to an often slightly yellow mass upon standing for some time.
The product such obtained has been recrystallized from water, in which it is extremely soluble, as well as from hot ethanol. In the first case
prismatic crystals are obtained, in the second case large silvery leafs.
The analysis of those gave values fitting for the formula NaSCO3H3* 2 H2O.
This compound is therefore identical to the "formaldehyde- sodium sulfoxylate" isolated in a different way by Reinking, Dehnel and Labhardt (2) from
BASF and Baumann, Thesmar and Frossard (3).
The reaction proceeds according to the equation
CH2O + Na2S2O4 + NaOH ----> NaSCO3H3 + Na2SO3.
(blah blah)
It is resistant against alkali and melts at 62°C.
Its solution gives no precipitate with barium chloride or calcium chloride, contrary to hydrosulfite or formaldehyde bisulfite, but sparingly soluble
salts with barium hydroxide or calcium hydroxide.
With NaOH, a double salt seems to form which has a higher solubility than the monosodium salt.
It is obtained as a syrup form the solid monosodium salt by addition of NaOH solution, or when more than 1 mol NaOH is used in the preparation of the
latter.
(some stuff about the barium salt)
With bisulfite, formaldehyde sulfoxylate forms sodium hydrosulfite (1).
In crystalline form, the latter is obtained by dissolving 1 part of the formaldehyde sulfoxylate in 1 part water and adding 3 parts sodium bisulfite
solution at 38- 40°C. After standing for 0,5-1 hour, sodium hydrosulfite begins to crystallize as the dihydrate:
NaSCO3H3 + 2 NaHSO3 -----> Na2S2O4 + NaHSO3*CH2O + H2O
With CaCl2, the solution of this regenerated salt forms the characteristic calcium salt.
(blah blah)
Analogous to the formaldehyde derivative, the other aldehyde-sodium sulfoxylates are obtained.
While the derivatives of the fatty aldehydes are easily soluble in water, the benzaldehyde derivative is sparingly soluble.
It crystallizes out if a 40°C warm sodium hydrosulfite solution is shaken with 1 mol NaOH and 1 mol benzaldehyde.
The analysis gives values fitting for the formula NaSO3C7H7.
The benzaldehyde derivative is not decomposed by NaOH at room temperature, contrary to the benzaldehyde bisulfite adduct.
In 2 mol NaOH it dissolves and can be reprecipitated by addition of acid.
Please post this version in the appropriate thread so that the whole community profits from it.
I can post the german article from which I translated this there if you wish.
Regards, Stefan |
So it seems simple enough!
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garage chemist
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So the necessary usage of NaOH was the missing information, right?
There was no mention of formaldehyde sulfonate at all in the article, it seems like this is not formed with NaOH.
Also, the NaOH stops the formaldehyde from forming the bisulfite adduct, right?
I don't really understand all the possible reactions here.
Anyway, I attached the german paper from which I translated this.
Attachment: Ber. 38, 1057.pdf (567kB)
This file has been downloaded 901 times
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Klute
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Yes, i think this is it.
As mentionned, dithionite hydrolyzes according to:
S2O42- + H2O --> SO2 2- + HSO3 2-
The sulfoxylate reacts with formaldehyde to form Rongalite, and in neutral conditions, the bisulfite forms the adduct. Adding enough NaOH semmingly
prevents this. Maybe K2CO3 would also do this, traces of K2CO3 would be less annoying for the reaction i plan on using it for than NaOH, so i might
try it out to compare.
The EtOH precipitation of the bisulfite is clever, apparently the differences in solubilities is big enough for this to effectively seperate the two
compounds.
I'm going to try this out a soon as i get my dithionite. Will give details.
Again, thanks alot GarageChemist, you cracked the case here! 
Danke!
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newme
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Hallo Klute
I am wondering if this method for the preparation of rongalite had worked with you.. sorry I know it is almost 4 years now but i am in need for this
compound . I have tried the method in a small scale but did not work with me..could not remove the bisulfite by addition of ethanol under cooling. I
know I am missing something but I do not know what exactly!
appreciate ur reply
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