06-06-04 17:46
No 511796
why cant sodium hydroxide be used to make the alkoxide salt of an alcohol for use in enolote synthesis?
is it because after evaporation you will end up with a hydrated salt that is no use in enolate synths?
(Hive Addict)
06-06-04 18:37
No 511799
because alkoxides are a stronger base than water?
anyway, if you'd utfse, you'd have found this:
Post 257912 (Antoncho: "Alkali metal alkoxides: finally, OTC!", Novel Discourse)
http://www.animalyawns.com
(Stranger)
06-06-04 21:14
No 511814
ok looks like swim finally has to read up on dissociation
and such..its just that when swim added NH4OH to iso alcohol the mix turned milky white, isnt this the alkoxide?
and wouldnt evaporation of the liquid leave the solid?
or does the statement "alkoxides r stronger bases than water" mean that as u evaperate the the mix and the water concentration increases ure left with alcohol and NaOH?
i think thats right and i thank u for makin me see it..thnx for the link dude
(Hive Addict)
06-06-04 22:19
No 511823
if you dissolve NaOH in alcohol and evaporate the alcohol, then
you'll get .... drumrolls .... NaOH.
if you want to make alkoxides, you need a stronger base than the
alkoxide. NaOH is weaker (not water, what was i thinking?).
http://www.animalyawns.com
(Heavyweight Chempion(eer))
06-07-04 03:18
No 511869
You can make the alkoxides by dissolving e.g. NaOH in EtOH and remove water to push the equilibria to the right. A convinient way is to distil of the EtOH/water azeotrope, preferebly with the aid of toluene.
NaOH + EtOH --> NaOEt + H2O
Severe Aztecoholic and President of Sooty's fanclub - Sooty for President!!
(Hive Bee)
06-07-04 10:32
No 511912
The post hypo referenced is very easy and very OTC.
Post 257912 (Antoncho: "Alkali metal alkoxides: finally, OTC!", Novel Discourse)
NaOH + CaO + EtOH -> NaOEt + Ca(OH)2(s)
The equilibrium is very much favoring the NaOEt.
CaO is very easy to make from limestone (chalk) if someone is bored and has a crucible and a really hot flame source or a kiln.
(Wonderful Personality)
06-07-04 14:50
No 511960
Barium, do you know the composition and bp of the ternary azeotrope formed by EtOH/H2O/toluene? I looked for this some time ago but couldnt find it....
Could the formed water be removed by means of calcium carbide?
(Hive Addict)
06-07-04 16:07
No 511970
> You can make the alkoxides by dissolving e.g. NaOH in EtOH and remove
> water to push the equilibria to the right.
sure, that's how the CaO method works. i just didn't want to bother
the newbee with 2 concepts at once (acid/base-strength and equilibrum)
.but say: wouldn't the azeotrope method need absolute (or > 96%) EtOH to start with?
http://www.animalyawns.com
(Hive Bee)
06-07-04 16:13
No 511973
Is this idea of azeotropic removal of water a proved method?
That would bee a nice method to get NaOEt!
Organikum: I don’t have the data for H2O:EtOH:toluene azeotrope but searching for it I found this table that might bee useful for some other occasion. Nothing here except benzene would come into play for NaOEt production, but we all know that we have to avoid benzene. It is interesting though, that toluene can replace benzene in practically all azeotropes.
A few three components azeotropes:
| A | B | C | boiling point |
| 7.4% H2O | 18.5% EtOH | 74.1% benzene | 64.9°C |
| 7.8% H2O | 9.0% EtOH | 83.2% ethylacetate | 70.3°C |
| 3.5% H2O | 4.0% EtOH | 92.5% CHCl3 | ? |
| 3.4% H2O | 10.4% EtOH | 86.2% CHCl3 | 61.8°C |
| 1.09% H2O | 6.55% EtOH | 92.36%CS2 | 41.34°C |
| 7.5% H2O | 18.7% i-PrOH | 73.7% benzene | 66.51°C |
| 8.6% H2O | 9.0% n-PrOH | 82.4% benzene | 68.48°C |
If you use calcium carbide you would end up with an etanolic solution of NaOEt and acetylene. You would have to boil the EtOH and acetylene off and isolate the solid NaOEt, which is even better. So, I see no reason why it would not work.
“The real drug-problem is that we need more and better drugs.” – J. Ott
(Chief Bee)
06-07-04 16:25
No 511977
If you use calcium carbide you would end up with an etanolic solution of NaOEt and acetylene.
Doesn't CaC2 react with alcohols to give calcium alkoxides and acetylene?
The Hive - Clandestine Chemists Without Borders
(Wonderful Personality)
06-07-04 17:15
No 511982
Patent US2796443 1956 to Dow Chemicals, describes a process for the production of alkali-alkoxides which requires no distillation. I basically works with an excess of hydroxide which saturates the water which can be withdrawn at the bottom, whereas the alcoholic anhydrous alcohol/alkoxide solution is withdrawn at top of a reactor.
Whuups. Alkoxide and anhydrous alcohol in one step. Nice, isnt it?
Rhodium: Drying EtOH with calcium carbide is an established method I thought up to now?
ADDON: Yes it is. Of course calcium alkoxide is formed, but this decomposes into alcohol and calcium hydroxide in the presence of water. Calcium hydroxide itself will NOT react with alcohol to form the alkoxide and so this is finished, the equilibrium shifts in the right direction...
(Heavyweight Chempion(eer))
06-07-04 17:38
No 511985
I am embarresed to say that I don't know the composition or the bp of the water/EtOH/toluene azeotrope.
Slightly off topic
Water removal by azeotropical distillation is overall a great way to dry both solvents and salts. I am surprised that it isn't used more to surpress the need of HCl/ether, HCl/IPA or HCl/toluene to make hydrochlorides in general. Regular 30-35% HCl in water can be used then with no problems if a simple Dean-Stark trap is available. Just neutralise the amine with your OTC hydrochloric acid add a couple of volumes of toluene (or xylene) and distill util no more water comes over. Then you have the hydrochloride suspended in the solvent ready for a recrystallisation. The only exception is if the hydrochloride furiously holds on to the last bit of water.
Perhaps this is worthy of a new thread?..
Severe Aztecoholic and President of Sooty's fanclub - Sooty for President!!
(Hive Bee)
06-07-04 19:12
No 512000
Patent US1978647
PS: good test Nicodem, because I was doing KOH/methanol in the meantime. voluminous, very fine precipitate, some of which goes right through doubled up real filter paper in the buchner, even with repeated passes through the filter cake. yes, the amount of acetone used is huge, there will be some drying experiments i'm sure.
PPS: i better mention the evil word "aldol". i think that is the correct thought here, but haven't looked in to it. the filter cake has to be washed with some solvent fast and well. this is not so bad on the original precipitation (not the best word, because its so fine it doesnt move down very fast) because whatever bad reaction between the base and acetone does not happen very fast. and the crystals come out instantly, as Nicodem says. you have at least 5 minutes before things darken, at least if you're using the same crappy chemicals that i am.
i used xylene, and the residue still had an acetone smell, and started to darken. its hot and humid here today, maybe the cake absorbed water in the short time that it was exposed, and this caused problems with the xylene wash.
http://www.archive.org/audio/etreelistin
(Hive Bee)
06-07-04 19:28
No 512006
Damn, I searched the net and there are tens of pages mentioning the H2O:EtOH:toluene azeotrope and none talks about its composition. Anyway, its b.p. is 74.6°C.
(see http://separationprocesses.com/Distillat
I know this is off topic, but I remember there was a discussion on how to azeotropicaly dry the acetic acid. Here is a method: http://separationprocesses.com/Distillat
EDIT
Gsus and Organikum, the patents you two found are excellent. I performed a preliminary test.
I first checked if concentrated aqueous NaOH is mishelable with ethanol. It is not. This means that the patent Organikum found is not bullshit but quite probably works!
Then I prepared an saturated ethanolic NaOH solution by heating a few grams of NaOH pellets in 15ml of commercial ethanol (96% ?). When cooled I decanted the liquid assuming that most of the water would remain on NaOH pellets like claimed in the Patent US2796443. I then treated the ~12ml of clear solution with 10ml of (not dried) acetone and a white crystalline precipitate immediately formed just as described in Patent US1978647. 10ml more of acetone was added and more precipitate formed.
It seems that quite a lot of acetone is needed for this method as it still forms more precipitate if some more acetone is added. But the patent claims that it can bee done all in one step before even preparing the ethanolic solution, therefore by simply mixing NaOH, EtOH and acetone. This should require less EtOH (as NaOH is only soluble up to ~12% in EtOH), but it should not give a pure product.
Anyway, the precipitate covered the bottom up to 5ml out of the 35ml total so it should not bee such a bad yield, though it looks somewhat fluffy and light. It looks quite crystalline like as opposed to NaOH, so it should bee NaOEt. I would have never thought that it is so easy. And NaOEt is such a precious and useful reagent.
“The real drug-problem is that we need more and better drugs.” – J. Ott
(Moderator)
06-10-04 04:45
No 512525
(Rated as: excellent)
According to CRC Handbook of Physics and Chemistry the boiling point of the ternary azeotrope of ethanol, water and toluene is 74.4 °C.
The percent compositions in the azeotrope are:
Ethanol 37.0
Toluene 51.0
Water 12.0
The composition of the uppper layer:
Ethanol 15.6
Toluene 81.3
Water 3.1
The composition of the lower layer:
Ethanol 54.8
Toluene 24.5
Water 20.7
The relative volume of the layers at 20 °C are
Upper 46.5
Lower 53.5
Specific gravity of layers
Upper 0.849
Lower 0.855
Chemistry is our Covalent Bond
(Hive Bee)
06-18-04 17:24
No 514130
My attempts to prepare some NaOEt as described by Nicodem in Post 512006 (Nicodem: "The patents work", Newbee Forum) failed, but I can't figure out why. Here is an outline of the procedure:
20 pellets of NaOH in 50 mL of EtOH were refluxed for about 2 hours. The mixture was allowed to cool to room temperature and ~20 mL of the solution was decanted into another flask. To this was then added 20 mL of acetone (not dried) and immediately some white, fluffy precipitate formed, but it disolved when the flask was shaken. Then the rest of the acetone was added, precipitate formed, but again it disolved upon shaking the flask. Unfortunately I ran out of acetone so I couldn't add any more.
So, what went wrong? My guess is that the amount of acetone added was to small to precipitate NaOEt, but I would like to hear some thoughts from more experienced bees.
(Hive Bee)
06-18-04 20:29
No 514159
Well, you already answered yourself with the first sentence:
20 pellets of NaOH in 50 mL of EtOH
A saturated ethanolic solution of NaOH is about 12 to 15%(depends on T). 50ml of EtOH can dissolve at least 6g of NaOH. Are you sure that 20 pellets is more than 6g? You need an excess of NaOH - you know this when there remains some that does not dissolve, not even with heating. Why did you reflux it anyway? I used heat just to dissolve NaOH as fast as possible since I was too impatient. Just let it stirr for some time and carefuly decant the saturated solution from the remaining NaOH pellets that will also retain some water on it. You also need at least twice the volume of acetone to precipitate a decent amount of the product.
PS: Don't forget to wash off the acetone after filtration or it will soon turn dark as acetone self condense with the aid of strong bases. I think they used ether in the patent, but you can get away cheaper by using toluene. Dry it in an exicator since water reacts with NaOEt and/or with vacuum.
“The real drug-problem is that we need more and better drugs.” – J. Ott
(Hive Bee)
06-18-04 22:17
No 514168
my favorite method for sodium ethoxide is to place 80 grams (2 moles) sodium hydroxide and 400 cc ethanol into a 1 liter flask and draw a line at the liquid level. then add 100 cc toluene and gently distill untill the liquid reaches the line and add 100 cc more toluene untill all the sodium hydroxide is converted to sodium ethoxide. this will take about 3 or 4 additions of toluene over about 2 or 3 hours. if you let atmoshperic oxygen get in the product will discolor (orange), but it is not neccesary to use an inert atmosphere to get a clean white product. the water (36 grams) is removed as the ternary azeotrope which will form in little bubbles from the sodium hydroxide as it disproportionates to sodium ethoxide. it will be easy to see when all the crystalline white sodium hydroxide is converted to a gelatinous mass of sodium ethoxide. gentle stirring is helpful but not essential. sodium ethoxide is very soluable in ethanol (24%) so don't discard the liquid as it contains substantial product. if you pour 2 moles of ethyl acetate mixed with 2 moles of acetone into this the mixture will immediataly solidify into what is most likely the sodium salt of the enolate of acetylacetone. patent says the process will work with all alcohols except methanol. maybe sodium methoxide could be formed by adding dry sodium ethoxide to methanol, this being driven to completion by sodium methoxide being insoluable in methanol.
(Hive Bee)
06-18-04 23:00
No 514171
my unscientific testing used at least 10X the volume of acetone compared to the unsaturated KOH/MeOH. the only shaking was with the filter cake and xylene. i mentioned huge amounts of acetone, and meant it. just add as much acetone as it takes for the solution to go white, and filter immediately. add more acetone to see if you precipitate any more. very simple if you have a good filter.
http://www.cursor.org