Bromosafrole Made Easy

[smiley_boy]

'Fuck stick' as a term of endearment? Must be some sort of regional colloquialism. It takes all kinds to make a world, I guess.

I'm glad to see we're all focused again on chemistry. If this HBr/HI gas generation works as well as you claim it to, I really think you have something here. I see that you brought it up once before, but I'm surprised there hasn't been more interest, especially when it comes to HI. I'm also surprised that this method isn't mentioned more often in the literature. This is really something exceptional. Well done; I really appreciate this.

Still, I have to disagree to your treatment of pKa's and their importance. The definition of 'pKa' is the negative natural logarithm of the ionic dissociation constant for a compound, and is not limited necessarily to dilute aqueous solutions; that's why whenever a pKa value is given in the literature, it usually comes with a few caveats (pKa measured at so-and-so degrees Celcius, in solvent X, in molar amounts of Y, etc.) You're absolutely right that there are many different ways of defining acids and bases, and different properties can be used to rank their strength.

Admittedly, the pKa's I used described their respective acid's activity in 1 M aqueous solutions at 25 C. And I stand steadfastly by my original statement -- under those conditions, HBr is hands-down more acidic than H₂SO₄. That's the quality by which I'm measuring relative acidity, its a perfectly reasonable and valid one, and by that standard, there is no other possible conclusion other than HBr is stronger than H₂SO₄. Period. If you truly believe that H₂SO₄ is stronger than HBr, I'm sure you'll be able to find hard numbers to back that statement up, and explain under which conditions this would be applicable.

I'm really not sure what you were trying to say with that quotation regarding superacids. What was that exactly supposed to prove? Sure, there are other systems by which to measure acids, but you haven't put forth anything specific, and you haven't provided any numbers. Sure, the acids' ranksing may be different using other measurements under other conditions, but without actual values to back that up, why should we believe it? Nope, the burden of proof rests on the side of the affirmative in any arguement, and if you truly believe you're right, then you'll have to give some hard evidense to back yourself if you want to convince people.

Now, moving on to bigger, better, and more practical things, like taking advantage of this new information you've given us. I think its important not to limit yourself with the idea of TSP as your only source of OTC phosphoric acid, especially due to its limited availability in many parts of the world. We must always "think outside of the box". Phosphoric acid itself is cheap and plentiful; its used as a food preservative, as well as a cleaning agent in the dairy industry. The local farm supply places sell phosphoric acid and polyphsophoric acid by the gallon, and its cheap. Buying it this way certainly beats trying to liberate it from a salt, that's for sure!

Still, if you don't have that available to you (which may be the case if you live in a non-dairy part of the world, like the modern urban jungle), you can always go the fertilizer route. Again, at many local farm supply places, a person can buy calcium hydrogen triphosphate and other related salts in big, huge sacks. This is where almost all phosphorous that is mined in the world ends up.

I have to say, this new HI/HBr preparative procedure is quite exciting. Do you have any experimental details available, or know where to find them? Somewhere in there, I imagine there's a solvent of some sort being used to whet the reagents, but what?

Anxiously awaiting more details,

- Smiley_Boy

[Bwiti]

"So at this point, we still have no procedure set out that we can point at and say: this is what everybody should use if gaseous HBr is what they want to make"

  I guess that the DMSO method is the safest way to go, but that kinda sucks for cheap bastards like me, because 1 gallon of DMSO + shipping costs about $45. Oh well, at least there's no fucking haz-mat fee!
 
  Here are some excuses to buy trisodium phosphate:

http://vm.cfsan.fda.gov/~dms/prodguid.html

"Ozone has been used to sanitize wash and flume water in packinghouse operations. Ultraviolet radiation may also be used to disinfect processing water. Chlorine dioxide, trisodium phosphate, and organic acids (such as lactic and acetic acids) have been studied for use as antimicrobial agents in produce wash water, although more research needs to be done. Operators should consider options for water sanitation most appropriate for their individual operations."

Check out Custom Building Products http://www.custombuildingproducts.com/onlyproducts/TSP%20DS.htm

Other uses:
Photographic Beveloper Ingredient
Denture Cleaner Formulations
Emulsifier And Neutralizer For Food



  I'm going to help all of you cleanse this diseased planet.

[Osmium]

> I guess that the DMSO method is the safest way to go, but
> that kinda sucks for cheap bastards like me, because 1
> gallon of DMSO + shipping costs about $45. Oh well, at
> least there's no fucking haz-mat fee!

Check the serious chemistry board. A few months ago I posted a much better way to bromosafrole there.

[foxy2]

Smiley
I am surprised by the lack of interest too, but who knows?
You want a procedure?
Well you should look at "THE MAN's Site" more often.

http://rhodium.lycaeum.org/chemistry/hydriodic.txt

Thanks Again Rhodium

 

Do Your Part To Win The War

[goiterjoe]

couldn't HBr gas be produced from an aqueous solution if the aqueous solution were saturated with HBr at extremely cold temperatures, and then heated to just below its boiling point?  I believe that HBr, as with most other haloacids, has a higher saturation concentration at lower temperatures than it does at higher temperatures.

If pacman influenced us, we'd glide around dark rooms eating pills and listen to repetitive music.

[lugh]

For those who are interested in knowing the time tested methods from "Inorganic Laboratory Preparations":
Hydrobromic Acid
Of the six methods given here, the first three may be used for the production of gaseous hydrogen bromide as well as for aqueous solutions of the gas; IV, V, and VI can be employed only for making the constant-boiling acid.

(I)
H2 + Br2 --> 2HBr
The following apparatus is assembled in order:
1. A gas-washing bottle filled with water.
2. A distilling flask filled with 50 ml of bromine cooled in ice with the inlet tube leading almost to the bottom of the flask.
3. A Pyrex tube, 50 cm long, packed with about 80 cm of activated charcoal which is held in place with glass wool plugs.
4. A U-tube filled with glass beads or porcelain chips coated with moist red phosphorus.
5. Two wash bottles in series filled with 100ml and 50ml of water, respectively; if constant-boiling acid is desired, the second bottle should contain 100ml of water. Both bottles are surrounded by an ice-salt bath. The reaction train is set up in the hood.
A steady flow of hydrogen is started through the apparatus to displace the air. This operation requires about thirty minutes, during which time the bromine is kept in the cooling bath.
The furnace is now slowly warmed to 350-375' C and the flow of hydrogen is increased to a point where the bubbles are just too rapid to count. A bath of water at 40-45' C is now placed under the vessel containing the bromine; under
these conditions, conversion to hydrogen bromide is complete in about 20 minutes. No vapors of bromine should be visible at the outlet of the reaction tube; otherwise the bromine must be cooled somewhat in water.
At the end of the experiment the two wash bottles are removed and the hydrobromic acid absorbed is determined from the gain in weight; if the smaller volume of water was used, the concentration of acid should be 60-65% by weight. If constant-boiling acid is desjred, the solution should be distilled and the fraction boiling at 122-127' C collected as 47-48% hydrobromic acid. A rapid method for determining the concentration of the solution produced is by a rough determination of specific gravity. 65%, 1.78; 60%, 1.68; 55%, 1.60; 50%, 1.52; 45%, 1.44.

(II)
2P + 3Br2 --> 3HBr + H3PO4
In a distilling flask fitted with a dropping funnel are placed 25 g of clean sand and, over this, a mixture of 25g of red phosphorus and l00 g of sand. The mass is moistened with 40-45ml of water, and 50 ml of bromine are introduced into the funnel. A U-tube and absorption bottles as described under (I) are connected to the flask. The reaction flask is cooled in ice while the bromine is added dropwise at a very slow rate; the phosphorus may glow with each addition of halogen. In order to avoid a suck-back of the water in the absorption flasks, it is advisable to place an empty safety trap between the U-tube and the water traps. As the reaction proceeds, the evolution of gas is more readily controlled and the cooling bath may be removed. When all the bromine has been added, the distilling flask is gently warmed to drive off the remaining acid vapors. The working-up of the hydrobromic acid solutions is the same as previously described.
Yield in I and II is over 90% of theory

(III)
C10H12 + 4Br3 ---> 4HBr + C10H8Br4
If anhydrous hydrogen bromide is desired, the procedure is carried out in the absence of water, using dry reagents. The apparatus of method II is used.
Thirty-five grams of tetrahydronaphthalene are placed in the flask with either 150 or 200ml of water, depending on the desired concentration of the acid. At first the flask is cooled in ice while 50ml of bromine are slowly added dropwise; about one gram of iron filings catalyzes the bromination. As the reaction proceeds, the flask may be allowed to warm up to room temperature. After all the bromine has been added the flask should be shaken for some time; the aqueous layer should be colorless. The acid layer is then separated from the organic material and worked up as in I.
Yield about 90%

(IV)
H2SO4 + KBr ---> HBr + KHSO4
A mixture of 120g of potassium bromide and 200ml of water is cooled in ice while 90ml of concentrated sulfuric acid is slowly added. The temperature must not rise over 75' C during this addition; otherwise free bromine may be formed, causing a loss in yield. The reaction mixture is cooled to room temperature and the potassium bisulfate is filtered off by suction through a fritted funnel or a hardened filter paper. The filtrate is then fractionated and the material boiling from 122-127' C is collected as constant-boiling acid.
Yield = 85%
In all cases where a mixture of sulfuric and hydrobromic acids is obtained, a redistillation is necessary to remove about 0.01% of sulfate in the first fractionation; only the acid with a steady boiling point is retained. This operation entails a loss of about 15% in yield.

(V)
Br2 + SO2 + 2H2O --> 2HBr + H2SO4
Fifty milliliters of bromine are covered with 200ml of water and sulfur dioxide is passed into the mixture, under the hood, until a straw-colored liquid results. Fractionation yields about 300g of 47-48 % acid, which is an almost theoretical yield.
As this reaction proceeds, the bromine dissolves in the hydrobromic acid that is formed, yielding a homogeneous liquid into which the sulfur dioxide may be more rapidly introduced.
HBr+Br2 <==> HBr2

(VI)
2S + Br2 --> S2Br3
S2Br3 + 5Br2 +8H2O -->12HBr + 2H2SO4
One hundred and fifty grams of bromine are weighed into a glass-stoppered bottle in the hood and l0g of powdered sulfur are quickly introduced. The bottle is then agitated and the sulfur rapidly dissolves to yield a red oily liquid.
Two hundred grams of ice are placed in a 500ml glass-stoppered bottle and the vessel is immersed in ice. About one-third of the sulfur-bromine mixture is added; over the course of about one hour the red oil disappears. Cooling is maintained throughout the hydrolysis. The second third of the sulfur-bromine compound is now  added, followed by the last portion about 30 minutes later. When all the material has dissolved and reacted, a pale yellow liquid remains which is fractionally distilled as usual; b.p. 122-127' C.
Yield about 300g of acid
Hydrobromic acid may be kept colorless for long periods of time by storage in a dark bottle in the refrigerator.
References:   
(I)  1. I, vol. 1:152.
(II) 2. FILETI AND CROSA, Gazz. chim. ital., 21:64 (1891); B:71
(III)3. I, vol. 1:151; footnote, p. 152.
(IV) 4. I, vol. 1:155.
(V)  5. Organic Syntheses, Collective Vol. 1, p. 23, Wiley, 1936.
(VI) 6. FARKAS et oL, J. Soc. Chem. Ind., 66:116 (1947).
     7. P:464.

[Agent_Smith]

Just to update on my ghetto experiment, oil has passed the foamy phase and is now back to dark colored oil/ no foam.  The oil layer isn't being absorbded as quickly as I'd hoped, however I've been quite lazy and left it off the swirler for most of Sun. and Mon.  The oil is brown / red, but not dark, still fully transparent.  The HBr layer (more appropriately the ion soup layer) is cloudy white (started off clear).

I'm convinced a reaction with 48% HBr will work (references are numerous), although the purity and concentration of mine might cause my attempt to fail.



blah blah blah something clever blah blah blah

[smiley_boy]

Foxy2,

Thanks for bringing that reference on Rhodium's page to my attention. Curiouser and curiouser. There are a couple peculiar things about the procedure as it is written. The first thing that caught my attention was that there's no reference; knowing where this came from would certainly be helpful (but beggars can't be choosers, I guess.) The second thing that I thought was strange is that there's no solvent, and though the reaction is run at 60 C, sodium dihydrogen phosphate has a mp of 95, meaning that as the phosphoric acid is used up, there'd be a mess of crystals, and reaction would have a difficult time going to completion, though maybe the mixture of salts causes a lowering in the melting point. But the thing that really made me wonder was the fact that they recommend using either 100 g NaI or KI, even though there is a considerable difference in the molar mass of these two salts, meaning a fairly large difference in the amount of final product.

This really has caught my attention. I'm going to do a little searching on my own, and see what I can find as far as where this idea originally came from (or at least, where published experimental details of this can be found.) There's a lot of ground to cover here, so I think it'll take a little time...

[lugh]

One reference you should check out is Ber. 23, 1642 (1890).

[Agent_Smith]

R.e. the lack of interest:  I knew about the phosphoric acid + NaBr stuff long ago, I just tried to work around it cuz phosphoric wasn't easy to get.  I found some TSP today, kudos to foxy for shownin me that one, I think I'll be making my own phosphoric now.

Hate to be a pest, but does the lack of comments on the experiment I have in progress mean that people don't know?

blah blah blah something clever blah blah blah

[lugh]

It turns out that the reaction of bromine with tetrahydronapthalene producing hydrogen bromide gas is an example of bromine reacting with many other hydrocarbons such as benzene, napthalene, anthracene or paraffin, as found in Anleitung zur Darstellung chemischer Praeparate by H. Erdmann (1890):

Pour 100 g of dry benzene into a flaks containing a few grams of anhydrous ferrous bromide, or fine iron powder, or aluminum powder. Run 135 cc of bromine very gradually into the flaks be means of separating funnel with the tube drawn out into a fine point. The flask should be put into cold water to prevent bromine or benzene from distilling over. When about half the bromine has been added, the reaction runs so quietly that the cooling is no longer necessary. The reaction is: C6H6 + 2Br2 --> C6H4Br2 + 2 HBr. To scrub the gas from the benzene and bromine vapors, pass the gas through a large U-tube, one leg which is filled with ferric bromide and the other with anthracene.

If one were to double the amount of benzene, one would have the same reaction for producing bromobenzene that is in Vogel's, which obviously produces hydrogen bromide gas along with bromobenzene.

As far the experiment, good luck, SWIM never had any with this route. If SWIM ever tries again, it will be using dry HBr gas in DCM as Osmium suggests.

[jim]

The only conclusion that I ever came to about the HBr/Safrole production of bromosafrole was that it needed to be done at low temperatures, room temperature being the ceiling for this one. 

The higher the temp. the greater the ether fission;  the lower the temp. the slower the bromination of the double bond...

You get the point.  I also don't beleive that the HBr method gets wonderful yields, I venture a guess of 75% tops...

[hmx777]

SWIM think this is the best bromo-addition method SWIM have seen:
(OCRed from J. Org. Chem. 1980, 45, 3527-3529)

Addition of Hydrohalogenic Acids to alkenes in Aqueous-Organic, 2-phase systems in
the presence of Catalytic amounts of onium Salts.
Experimental Section
The general procedure for the preparation of 2-bromododecane is as follows. A mixture of 16.8 g of 1-docecene (0.1 mol), 55.5 mL of 48% hydrobromic acid (0.5 mol), and 5.1 g of hexadecyltributylphosphonium bromide (0.01 mol) is heated at 115 °C (bath temperature) with magnetic stirring for 2 h. After this time, NMR analysis shows a 94% conversion into 2-bromododecane. The organic layer is separated, the aqueous phase is extracted with dichloromethane, and the solvent is evaporated. The resulting oil is distilled to give 21.4 g (86.0%) of pure 2-bromododecane: by 125-126 °C (9 mm); n22 D 1.4594 [lit .5 by 125-130 °C (10 mm); n2lD 1.4600]. By treatment of the distillation residue with petroleum ether 4.8 g (94.0%) of phosphonium bromide [mp 52-54 °C (lit.' mp 54 °C)] is recovered, which can be reused without further purification.

SWIM is sure other PTCs can also be tried.

[Rhodium]

Yes, this procedure has been tried on safrole (see halosafrole.txt on my page) with Aliquat 336, and was found to work satisfactorily with 37% HCl, but not with 48% HBr, in the latter case the methylenedioxy bridge was cleaved.

http://rhodium.lycaeum.org