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unionised
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Praseodym,
If you had read my post you would know that I don't have sodium, that's why I'm playing this game.
Also, if you read the title of the thread, you would realise that the solubillity of metal alkoxides in water is of rather limited relevance.
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bio2
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.......solubillity of metal alkoxides in water is of rather limited relevance............
I'll say; the shit decomposes back to the starting alcohol.
With Al methoxide it is not instant but can be observed occuring over a few minutes at test tube scale. Solubility is said for PhMe, benzene etc. but
it ain't much. Even at the boiling point of toluene very little of the methoxide dissolves.
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Dr.Muto
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sodium ethoxide//metallic sodium
Thanks 2 all 4 all the comentary on this topic. Not as positive as I would have liked, but much better than I thought it would be. Mostly sounds like
a viable pain in the ass. Viable none the less.
......................................................................................................... Any tricks to the electrolysis of Naoh
anyone can enlighten me to?
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neutrino
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There are a number of threads about sodium production in technochemistry.
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Rosco Bodine
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Hmmmm , I keep having this thought that *possibly*
simply dissolving NaOH in ethanol and subjecting
to electrolysis should produce sodium ethoxide .
At first , all that would be occuring is elimination of any
water which is present , but after that , the product
should be sodium ethoxide content increasing as NaOH content decreases in the alcohol , with H2 evolving at the cathode and O2 at the anode .
A simple cell design like a jar having a plastic lid with
two parallel carbon rods , one for the cathode and one for the anode , is possibly all that would be required .
The cell resistance could be high so it might lead to needing a cooled cell or reflux condenser to prevent
excessive evaporation of the alcohol . Compared with
the simplicity of the method which Organikum has
posted here , there seems no advantage to an electrolytic
method , though it may be a valid alternative .
Anyway , attached here is the patent mentioned by Organikum at the beginning of the thread .
[Edited on 1-9-2006 by Rosco Bodine]
Attachment: US2796443 Sodium Ethoxide.pdf (279kB)
This file has been downloaded 1679 times
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Marvin
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As much as I hate to be a stickler for scientific accuracy. Hmm, thats a lie, it is my reason d'entre, but lets pretend I do for the moment....
"Compared with the simplicity of the method which Organikum has
posted here"
Which there is no evidence works for alkoxide. The description is heavily simplified from the patent, which is counter current based.
I suspect electrolysis would probably not yeild oxygen, but rather oxidise the ethanol to produce aldehyde, which would then condense in the strong
base to produce more water and unhelpful products.
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Rosco Bodine
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Yes it is likely that Organikum simply cannot be trusted 
However , setting aside the political credibility issue in the interest of science  , ........
After all *if* it is a simple solubility driven equilibrium reaction as the patent states , the reaction should proceed to the right according to the
greater affinity of the solid hydroxide for water . The hydroxide in excess wins the battle for the water . If this holds true , then the counter
current scheme is simply a means of continuous production convenient on an industrial scale , as an efficent method , and keeping the apparatus
compact in size . But for a laboratory method , the same reaction should be accomplished simply by long stirring of an excess of what NaOH will be
dissolved in
ethanol heated to near its boiling point . Over time the
same equilibrium will be reached . The liquid portions
should separate on standing and the upper layer of
ethoxide in alcohol could be pipetted or decanted ,
or the whole of the liquids decanted from the solids
into a separatory funnel . Perhaps some sort of color indicator could be used to distinguish the phases if needed , but I am going to guess that the
ethoxide layer will likely have a slightly yellowish cast and the interface
should be visible .
Dow is a huge chemical company , so it seems unlikely that one of their patents would be total bullshit .
The experiment to examine this is as simple as I have described , and I will get around to it myself unless
someone else beats me to it first .
As for the electrolysis oxidizing the alcohol , perhaps
and that may depend upon the anode material alone ,
or it may require a partitioned cell ....I do not know ,
and I would bet good money that you don't know either .
Until experimental results are found , then my theory , hypothesis , guess or speculation , is as good as yours
and so is Organikums .
Azeotropic removal of water from a non-excess of NaOH in ethanol by using a benzene additive to the mixture to create a ternary system of
ethanol-benzene-water , which distills away and from which the water can be separated in a Barrett water trap , leads to a solution of sodium ethoxide
in the dried ethanol in the distillation flask . See the patent attached . This is simply another way of shifting the same
reaction equilibrium to the right , correct ?
In another thread someone mentioned having experimented with toluene as an alternative to benzene
described in an even older patent .
Attachment: GB377631 Sodium Ethoxide via Azeotroping.pdf (169kB)
This file has been downloaded 1631 times
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not_important
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The azeotropic method is used commercially. Petroleum ether can be used instead of benzene, even though it's a mix you'll still get an azeotrope
effect.
The earlier patent depends of the counterflow to drive the reaction to completion. As the solution moves up the column, there's less and less water
for the right hand side of the equilibrium. To do the same thing in a beaker or flask, you would need to repeatedly remove the aqueous layer to change
the conditions, or dump in a huge amount of hydroxide. The patent explicitly talks about batch mode, where no replacement hydroxide is added. The
system is almost like a reactive column, giving products that seem out of equilibrium with the expected result from the ratios of reactants.
An alternative to third component azeotropic distillation is to dry the water-alcohol azeotrope vapour with cornmeal, then condense the dry alcohol
for return to the reaction vessel :
http://journeytoforever.org/biofuel_library/ethanol_grits.ht...
I had the same idea as you regarding electrolysis of a hydroxide-alcohol mix some time ago, and tried it. Started with 95% ethanol, the current did
drop off as the water was removed and eventually effectively stopped; the power supply I was using couldn't put out much voltage. There were some
non-alcohol oders, discolouring of the solution, and gunk on the electrode. Given that alcohols can be oxidised by air/O2 in the presence of strong
base, I believe that was what was happening. However it did not appear to be the primary reaction path. The concept may be practical using a low
current density and anode with low oxygen overvoltage. Even if not practica on its own, it might work to remove the last of the water from the
hydroxide column method.
For real production one could possibly use pervaporation to pull the remaining water and some alcohol out of the alcohol-alcoholate, run that takeoff
through a second higher temperature pervaporater to concentrate the water phase, and use hot xylene to azeotrope off the water from the
water-hydroxide phase to recover the hydroxide for reuse. Larger scale than a lab needs, but a nice system. Like reactive columns, it's one of those
processes that are on the edge of being too big for lab use.
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Rosco Bodine
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*If * the NaOH formed a series of solid crystalline hydrates having higher and higher vapor pressures of water , instead of simply dissolving directly
and separating as an aqueous phase descending , then I could better believe in that idea that the reaction is
dependant on a progressing reaction zone which is dependant upon a more and more anhydrous condition higher and higher in the column being supplied
from the bottom . But the way I see this reaction is that it is a *simple equilibrium* between saturated aqueous NaOH
and the alcohol solution of sodium ethoxide .
The reaction column is only supplied from the bottom in order to provide for gravity separation of the reaction products in the reaction vessel , to
avoid requirement of a second vessel for performing the separation of the phases , and allow for the process to be operated continuously ......it is a
matter of mechanical design for
convenience of manipulation of materials and economy , not for necessity of the reaction conditions . The reaction should proceed to the exact same
equilibrium with everything mixed together in a single reaction zone ,
since there is no chemical difference at the surface of the solid hydroxide anywhere in the column , other than the thickness of the adherent * film *
layer of saturated
* aqueous * solution on the pellets or granules of sodium hydroxide .
What seems to be the debate here is semantics about
whether the patents column of hydroxide is a counter current reactor in the classical sense ( which it is not ) ,
from my impression of it anyway , it is a simple reactor
separator . If you consider the case where the pellets
of hydroxide used would be the potassium salt , it is
already the case that perhaps 12-15% water is present
in the fresh pellets which would be unreacted material
at the top of the column at the very start , because of
the virtual impossibility of securing the potassium hydroxide as the anhydrous material . The tenacity of
the fused hydroxide for that much water content even
at fusion temperatures prevents its further dehydration
in common manufacture ......so it isn't a matter of having
any requirement for the absolutely anhydrous material to be at the top of the column , because that condition would not be the case anyway .
Therefore , is further
evidence that the equilibrium is related to physical
* film chemistry * of the aqueous layer of hydroxide
accumulation on the solid particles of hydroxide , which
grows in thickness and coalesces into droplets which
precipitate , settling out at the bottom .
It is a simple " salting out " driven equilibrium analogous to what would happen happen if 70% isopropanol was
shaken together with an excess of solid sodium chloride ,
which would result in a phase separation , having something 92% or higher isopropanol in a dehydrated
upper phase , where the salt has won the battle for the water and separated as a brine in the lower phase .
This could also be be done in a column like the patent ,
but the same equilibrium would be reached , and the same result on separation .
[Edited on 1-9-2006 by Rosco Bodine]
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Rosco Bodine
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We have here Organikum and Rosco sitting side by side
on the trick board over the dunk tank , mercilessly ridiculing the crowd of novice baseball pitchers .....
Todays " two for the price of one special "
Could it be they will stay dry , or is it bath time
for the reaction dynamic duo ?
Okay all you physical chemistry apprentices
it's three balls for a dollar , so step right up
and take your best shot
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Marvin
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This is why there is so much shit on the internet. Someone takes a possibly good method they don't completely understand and takes out the parts they
don't think are needed to make it easier. I'm not blaming Organikum, its more likley to have been a hive modification anyway, but I will certainly
blame him for passing on an incomplete method as 'Tried and true' which he later climbs down from as far as "I thought I read somebody doing it with
success" for production of methoxide. There is also a gap in the claims made by the patent for the ethanol/ethoxide varient that suggest a problem,
either of loss of ethanol in the effluent at the base of the column, a higher than it would be advisable to brag about level of hydroxide in the
product, or both, and this is when the patent method is followed to the letter.
"Yes it is likely that Organikum simply cannot be trusted"
Organikum has said "I want to point out that I posted the method mainly for making anhydrous alcohol, not ethoxide".
This could well be successful.
He has also said "The working principle is solubility, density and salting out - counterflow makes it continous,"
This is WRONG and contradicts the explanation in the patent.
You have said "After all *if* it is a simple solubility driven equilibrium reaction as the patent states"
Show me where.
"The hydroxide in excess wins the battle for the water . If this holds true , then the counter current scheme is simply a means of continuous
production"
This does not hold true for any reasonable excess, and the patent explanation is clear on why the counter current system is not just a means of
continuous production but integral to the invention. Looking at the crude batch interpretation at the top of the thread, you have a single
equilibrium between the water, alcohol, alkoxide and hydroxide, and the hope this will be enough to drive it mostly to alkoxide. Even in the batch
method of the patent it is still a counter current method and is not the same. While the drawing suggests a tall vat, it isn't, its a column and this
is made very clear in the text.
Lets take 2 mins to think about the properties of, for example freshly fused KOH as a dehydrating agent. Initially it's very powerful, that is to say
it has one of the lowest partial pressures of water of anything in common use, but its capacity at this level is very low. As it has to absorb more
and more water the partial pressure rises sharply. As it dissolves in its own water this is a fairly high capacity drying agent, but it is not very
powerful. The dilemma, is that in drying a substance you get these properties in the wrong order. The initial powerful drying action occurs when the
compound being dried is very wet, and a high capacity drying agent is needed to remove the bulk of the water, while the last stages of drying, when
the most powerful drying action is needed occurs when the drying agent is saturated with all the water previously soaked up. The question is, can you
reverse this order, to achieve an ultimate water content close to the fused KOH point, and yet still use the full capacity it ends up dissolving in
the water.
Quoting from the patent "In operation the reaction equilibrium will be progressivly shifted throughout the column'. This is why it works. The
hydroxide and alcohol are put through the column in counter current. The equilbrium at the bottom is wet/liquid hydroxide contacting the alcohol as
added and ending up mainly as a dried alcohol/hydroxide and a seperate layer of mainly hydroxide and water.
As you move higher up the column, the rising hydroxide/alcohol solution meets progressivly drier falling solid hydroxide, water is removed and the
equilibrium between hydroxide in solution and alkoxide is shifted a little bit more towards alkoxide.
At the top you have a solution of hydroxide and alkoxide in anhydrous alcohol contacting solid anhydrous hydroxide freshly as it is added, driving the
conversion to alkoxide as far as it can go, before the liquid at the top is removed as the product.
The very powerful drying action of anhydrous hydroxide is being used where it is needed, at the top to shift the equilibrium as far as possible
towards alkoxide. As it moves down the column it progressivly absorbs more water and becomes a weaker dehydrating agent. This is not a problem as it
is constantly contacting rising alcohol/hydroxide/alkoxide/water equilibriums with less alkoxide and more water that is easier to remove, until at the
bottom at its weakest it is in contact with fresh alcohol being added. If the level of water at the point is enough to alow the hydroxide to form a
seperate layer it will and the effluent is a solution containing mainly hydroxide and water with hopefully only a small amount of alcohol.
As another example of a counter current method, and the difference in the results by using it, production of liquid air by venturi expansion
(Regenerative process). Depending on the degree of compression, with no counter current you end up with 5 or maybe as much as 20 degrees cooling
which is produced by the nozzel and when the aperatus has cooled to this temperature it is spat out the exhaust. Add counter current exchange between
the incoming compressed air and the exhaust however and you get an exhaust neer inlet temperature, and the core goes down as much as 300 degrees below
inlet at which point the air liquifies. Counter current is a way to push things up the entropy slope. 20 degrees without, 300 degrees with. The
energy of course is still the same, but the degree of completion is so much higher.
"Dow is a huge chemical company , so it seems unlikely that one of their patents would be total bullshit ."
While that logic is flawed, it certainly helps if you read and understand the patent.
You can taunt the novice pitchers all you like, but while new to baseball some may turn out to be already rather good at cricket.
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Rosco Bodine
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You are basically declaring that the hydroxide itself
has different levels of hydration according to its height
in the column , wetter at the bottom and drier at the top ,
when this simply is not true .
Only the ethanol with its dissolved components is
wetter at the bottom and drier at the top due to time
of contact with the dehydrating agent , the composition of which is constant , except for the thickness of the aqueous film on its surface .....and
the thickness of
that film hasn't any bearing whatsoever on its vapor pressure , but only upon the surface tension which
when exceeded by gravity allows that film to coalesce into droplets .
The thinner film of aqueous hydroxide solution on the hydroxide pellets at the top of the column has no greater dehydrating property than the thicker
film of hydroxide
solution on the pellets low in the column , which is actually coalescing and sloughing off .
The dehydrating power of the pellets is *constant* regardless of their height in the column , it is only
the ethanol solution of hydroxide itself that is being
gradually dehydrated over time of passage through
the dessicant .
The hydroxide dessicant in this case is not functioning
in the manner of of a dehydrated salt which would
be absorbing water to arrive at a specified hydration
state for " crystal water " being held in a solid . Fused
pellets of hydroxide are not like sponges , not capable
of physically trapping water , but their dessicant property
is due to a surface reaction of deliquescence . The
affinty for water is to form a saturated solution , which
has a uniform vapor pressure and a constant water
content . So great is the affinity for water that the
solid hydroxide will attract even water vapor from gases ,
or salt out the water from solvents to form an aqueous brine which separates as it does in this case .
This desssicant system is based upon the vapor pressure
of the saturated aqueous solution of hydroxide in contact
with undissolved solid hydroxide which maintains the saturated condition of that liquid solution , whether it
is a pool at the bottom of the column , or a film of varying thickness residing on the surface of the solid hydroxide ,
the vapor pressure remaining the same , and the solid hydroxide dissolving as needed to regulate that vapor pressure .
The alcohol phase is simply stripped of more and more water from time of contact with that dessicant system .
Heat is what makes this thing go , like most reactions .
At 70C , the deliquescence is augmented greatly over what
it is at room temperature , in contact with solution water
available in a solvent like alcohol , because the already great solubility of NaOH in water is driven even higher , and proportionally the NaOH has an
even greater affinity for
the water , than for the alcohol , as the solubility curves should confirm .
[Edited on 3-9-2006 by Rosco Bodine]
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Nicodem
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There is a lot of confusion regarding this patent, a confusion which was mainly created from wild speculation reasonably originating from the distrust
that sodium or potassium ethoxide and their higher alkoxydes can be prepared so simply when in every lab in the world they are either acquired or
prepared from sodium and potassium metal.
I have not followed the whole thread, only its beginnings and even that I mostly forgot, so I apologize if I declare something that was thoroughly
discussed and is not an issue anymore. My goal is only to bring back some confidence in the patent. Otherwise the beginners will be repulsed from
using it and remain without alkoxydes for the rest of their lives. I personally don’t care for myself as I have reagent grade NaOEt, but I do know
how it fells being without it when so many reactions call for this very useful reagent.
So I though to only add these observations and claims to the discussion:
The comprehension that the equation EtOH + OH(-) <=> EtO(-) + H2O lies strongly to the left is generally misunderstood. All you need to
check are the relevant pKa's of EtOH and H2O to see that they differ very little. If one makes a solution of NaOH in absolute EtOH, the value of
[EtOH] will always be much higher than [H2O] and if this is considered in the reaction constant equation you can see that even though ethoxyde is a
little more basic than hydroxide the concentration of the other two reaction components compensate in the opposite direction: K = ([EtO(-)][H2O]) /
([EtOH][OH(-)]).
Conclusion: Ethanolic solution of NaOH contain a lot of ethoxide ions in relation with the hydroxide ions.
The prejudice that sodium ethoxyde and similar alkoxydes are exceedingly difficult to prepare by a hobby chemist is based only on the
awareness of how this is done in the professional labs. But what our dear hobby chemists don’t take into account is that it is done so because
sodium metal is cheap, available in nearly every lab and due to the awareness that this method is simple and reliable in its performance (unlike
various other methods more adapted to be industrial processes as the patent in question is).
Conclusion: Producing alkoxydes higher than methoxyde, without resorting to sodium or potassium metal, is no big deal.
The assuredness that H2O created in the hydroxide/ethoxide is difficult to remove from the NaOH/KOH ethanolic solutions is in appearance based
on the false or even unconscious belief that an equilibrium component of a reaction can not be “kidnapped” out of the reaction just like this. Its
participation in the equilibrium has no importance whatsoever in how difficult it is to abstract, the only thing that matters is the concentration of
its free form and this is the only link with the equilibrium. Thus H2O can be taken out of NaOH/KOH ethanolic solutions since its concentration can be
considerable. And for each amount of H2O that is taken out, a new, just slightly lower amount (by the rules of the equilibrium constant) is formed.
Check Vogel’s section on drying ethanol where it nicely explains why ethanol can not be dried with alkali hydroxides (because the ethoxyde is left
in the distillation flask and the azeotrope is obtained in the receiving flask!). Even more, according to US1978647 one can precipitate NaOEt from
NaOH ethanolic solution by simply diluting with acetone which reduces its solubility!
Conclusion: The H2O in NaOH/KOH alcoholic solutions is not mysteriously bound, only its concentration is bound to the reaction equilibrium.
Water can be easily physically taken away from the alkoxyde (by azeotropic removal or salting out, for example) and correspondingly can the alkoxyde
be physically separated (by precipitating with acetone, for example).
The confusion that if you would get an ethanolic solution, for example 90% NaOEt : 10% NaOH or even worse, would mean you failed in obtaining
the pure sodium ethoxyde. This resulted in claims that Organikum’s modification of the patent procedure is faulty. Too soon! This is not yet pure
NaOEt but its solution. One needs to get rid of the ethanol first and this is generally done by distillation (later on a vacuum distillation should be
applied in the last stage of drying NaOEt). As the previously said, the hydroxide will be transformed to the ethoxyde in the drying process by means
of azeotropic removal of the equilibrium formed H2O. If one is unsure if there is enough ethanol to entrain all the formed H2O, he can still add a
little toluene to form the more efficient ternary azeotrope and make the process full proof.
Conclusion: Organikum’s modification can only be considered faulty as a method of preparing truly and absolutely dry ethanol, but as a method
of NaOEt production there is no reason to believe it does not work. Even the so obtained dried ethanol is dry enough for many uses. Therefore, one has
to consider his concept of “anhydrous” before calling Organikum’s method of drying ethanol faulty.
[Edited on 3-9-2006 by Nicodem]
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Rosco Bodine
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So what about Rosco's modification ?
The patent you mentioned is attached and bears out what I have been saying .
Thank You
Just to be clear , this reaction should proceed towards the right without any counter current scheme
at all , simply by having * solid * NaOH always present
in excess in the reaction mixture maintained for awhile near the bp of the ethanol .
When the hot mixture reaches equilibrium , the alcohol phase will contain predominately the ethoxide as its dissolved sodium compound .
[Edited on 3-9-2006 by Rosco Bodine]
Attachment: US1978647 Acetone Precipitation of Sodium Ethoxide.pdf (201kB)
This file has been downloaded 1645 times
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Marvin
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"After all *if* it is a simple solubility driven equilibrium reaction as the patent states"
I am guessing that since you did not substantiate this in either of the two posts following my request that it is simply untrue.
"The thinner film of aqueous hydroxide solution on the hydroxide pellets at the top of the column has no greater dehydrating property than the...."
I would agree that I also do not consider mechanical reasons to be worth arguing for the performance of the column, or kinetic ones. If reaction rate
is the issue a home chemist can always wait longer.
I would state that such possible effects as K2O produced by heating the KOH isn't worth thinking about, to all real intents and purposes it doesn't
happen.
I would insist that KOH and NaOH as powders have surface absorbtion properties that are very strong, but I concede that these effects are probably not
important on the molar scales in the context of this thread and would not by themselves prove my argument.
"their desiccant property is due to a surface reaction of deliquescence . The affinity for water is to form a saturated solution , which has a uniform
vapor pressure "
You are stating that the deliquescence is the basis of the dehydrating power, and that while solid KOH (for example) is in contact with the resulting
saturated solution a change in the overhead vapour pressure of water would cause more or less KOH to dissolve until equilibrium is again reached.
Since the composition of the solid, and that of the solution don't change only their amounts do, the vapour pressure of water must be constant while
both exist. I can't fault the logic. The bad news is that the chemistry is wrong. At RTP solid anhydrous KOH will absorb water, neglecting surface
kinetic effects it will continue to do so until it is entirely converted into the monohydrate, which is solid. KOH.H2O will continue to absorb water
with slightly less enthusiasm until it is converted entirely to the dihydrate which is...... solid. KOH.2H2O will continue to absorb water with
slightly less enthusiasm still until entirely converted to KOH.4H2O which is a liquid. I say liquid and not solution, because it really is a molten
hydrated salt, if you cool it you get KOH.4H2O as crystals. The behavior of the solution then gets more complicated, but is outside the required
scope for this thread and beyond any reference material in my home library anyway. Sodium, rubidium and Caesium hydroxide have at least 1 solid
hydrate each at RTP in addition to the solid 'anhydrous' forms. I use the term with care as in very old textbooks the anhydrous XOH are themselves
considered to be hydrates of X2O, so to be clear an XOH and at least one XOH.nH2O both solid at RTP. In the case of sodium there are in total about a
half dozen individually distinct hydrates mostly liquid at RTP. Returning to KOH and the patent, at the temperature of the column the anhydrous form
and monohydrated forms are solid, the dihydrate and tetrahydrate are miscible liquids, being a changing mixture the dehydrating power is continuously
variable depending on its composition. So depending on the point in the column you are looking at you have anhydrous/monohydrate desiccant or
monohydrate (solid)/dihydrate (liquid eventually, there is no requirement for a sharp change in melting point) or a liquid consisting of varied
proportions of the dihydrate and the tetrahydrate, and with a desiccating power that depends on the ratio in the active phase.
"You are basically declaring that the hydroxide itself has different levels of hydration according to its height in the column , wetter at the bottom
and drier at the top "
Yes, that is exactly what I'm stating.
Nicodem,
There is no one here that is challenging the claims in the patent, which renders most of your post a cheerleading chant for a nonexistent cause. The
question in the thread is on exactly how the process in the patent works, and if the modification proposed at the top of this thread is equivalent.
You do also provide a number of important facts.
"Conclusion: Ethanolic solution of NaOH contain a lot of ethoxide ions in relation with the hydroxide ions."
This is certainly true, and a dilute solution of sodium hydroxide in absolute ethanol can be nearly 100% ethoxide. Ethoxide is the stronger base
though, and simply adding an acid, ethanol, to a base, sodium hydroxide, cannot result in a solution that is more strongly basic unless something is
doing work. These reactions must be pushed up hill. Of course required purity and solvent is strongly dependant on what the ethoxide is going to be
used for. A second point, is that with hydroxide and ethoxide (and water) in the same mix, if the hydroxide is kinetically better than the ethoxide,
even a small amount may do a disproportionate amount of damage, as the hydroxide is used up more will be created as ethoxide is destroyed by water to
maintain the equilibrium. While your conclusion can well be true, on its own it doesn't mean anything.
"The prejudice that sodium ethoxyde and similar alkoxydes are exceedingly difficult to prepare by a hobby chemist ...."
"Conclusion: Producing alkoxydes higher than methoxyde, without resorting to sodium or potassium metal, is no big deal."
Your conclusion does not follow by any logical or chemical means. This is just rhetoric.
"The H2O in NaOH/KOH alcoholic solutions is not mysteriously bound, only its concentration is bound... "
This may be a useful conclusion, had someone actually assumed this. No one has.
"Conclusion: Organikum’s modification can only be considered faulty as a method of preparing truly and absolutely dry ethanol, but as a method of
NaOEt production there is no reason to believe it does not work"
I find it interesting that Organikum's method as an absolute alcohol process is flawed, this passed me by completely, much thanks for bringing the
Vogel information to our attention. The second part to your conclusion does not follow logically unless two conditions are met, firstly that the
distillation is done slowly with a fractionating column, when azeotropic distillation would dehydrate the remaining hydroxide/ethoxide mixture, a
simple or rapid distillation could well fail to further conversion. Secondly it relies on the degree of dehydration of the alcohol used to exceed the
water produced by the conversion of hydroxide to ethoxide. Otherwise alcohol will be exhausted as azeotrope before all the hydroxide is gone. Since
the alcohol Organikum is using is wet, and no directions on distilling are given neither of these conditions are automatically met and there is
considerable question as to how successful it is as a complete method. With modifications though, it could well be made to work with more complicated
means and equipment. If the amount of dehydration of the wet alcohol below azeotropic by the sodium hydroxide removed exceeds the amount required to
dehydrate the sodium hydroxide that remains dissolved in it, then following fractionation substantial conversion to ethoxide should occur. There are
a lot of variables though and the conditions are a long way from being automatically satisfied.
In other words there is every reason to believe it does not simply work as stated.
In addition to previously discussed trinary azeotropic methods, sodium alkoxides can be produced using magnesium metal as detailed elsewhere and in
Fieser as a method for making very dry alcohol (Magnesium hydroxide being insoluble in the mixture, the ethanol is decanted and distilled off from
remaining magnesium ethoxide).
The acetone method is new to me, and I find it suspect. Not because the production of sodium ethoxide by precipitation seems so unusual, but because
acetone is well known for being incompatible with strong bases.
Rosco,
"At 70C , the deliquescence is augmented greatly over what it is at room temperature , in contact with solution water "
Having shown the mechanism of dehydration to be different to that assumed this no longer makes sense either. While hydroxide will be more soluble in
the water the real question is the vapour pressure over a hydrates salt, which generally increases somewhat with increasing temperature. Heat will
certainly reach equilibrium faster, but it may turn out to be better to let the system cool after and crystalise more of the hydroxide as a hydrate.
"Just to be clear , this reaction should proceed towards the right without any counter current scheme at all , simply by having * solid * NaOH always
present in excess in the reaction mixture maintained for awhile near the bp of the ethanol "
There are no claims in the patent regarding sodium ethoxide, so just the use of sodium hydroxide and ethanol in the full process may produce
unacceptable results and stretches the patent as evidence beyond its breaking point. At best had the yield been higher they would have listed this
instead. At worst it does nothing useful at all. This is why I've concentrated my examples on KOH, which the patent can be considered fair evidence
for success in the column.
I think it is now clear why a counter current is so important, as put forward and explained by not_important and myself.
Modifying the method may be feasible, much larger excess of hydroxide, fractional distillation of the remaining ethanol, but this is something that
would have to be done experimentally. Its not about the potential of a method to do well by our limited understanding of the chemistry, it's about
evidence and reliability.
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Nicodem
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| Quote: | Originally posted by Marvin
Nicodem,
There is no one here that is challenging the claims in the patent, which renders most of your post a cheerleading chant for a nonexistent cause.
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But that is exactly what I wanted it to be. 
I believe there are still a bunch of hobby chemists who question the patent and there are still many others who don’t even realize that producing
NaOEt from NaOH is possible. I did not want to intrude in the “Marvin vs. Rosco debate” about the mechanism behind the NaOEt formation by that
process, since it is obvious to me that it is a dehydration process where the ethoxyde/hydroxide ratio exponentially raises with the distance up the
column. This is already evident from the equilibrium constant equation and the partition theory of extractions. Furthermore, since the increase of the
ratio is exponential with an already good starting point, I would say that one or two Organikum’s partitioning of H2O among conc. NaOH(aq) and conc.
NaOH/NaOEt(EtOH) gives a relatively satisfactory resulting purity for the NaOEt produced after distilling off the solvent. Its purity should be enough
for most uses (meaning >90%).
As for the other details of the current debate, I’m not really interested enough nor am I competent enough, but I see it mostly as another annoyance
that may deter experimenters to use this method or its variants. If you two are working together to find out an optimization then that is just great,
but unfortunately it does not look like this at all.
| Quote: | | The acetone method is new to me, and I find it suspect. Not because the production of sodium ethoxide by precipitation seems so unusual, but because
acetone is well known for being incompatible with strong bases. |
But at least it was verified by me and another Hive member that I currently don’t remember the name. The link to The Hive at the beginning of this
thread points to the particular discussion on NaOEt where this and many other useful things were mentioned.
Acetone slowly self condense to diacetone alcohol in the presence of ethoxyde or hydroxide. This is however not very relevant as the exposure of
acetone lasts only a couple of minutes, the time it takes to filter the precipitate which must be washed with a volatile aprotic non polar solvent
(petroleum ether, ether, toluene etc.) to remove acetone remains and any side products thereof. This is explicitly mentioned in the patent. Higher
condensation products from acetone exposed to strong bases only occur after prolonged exposure or heating which is irrelevant to this method.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Rosco Bodine
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The patent states that the operative requirement for
the amount of excess alkali hydroxide , is a minimum of
0.1 mole to a maximum of 0.4 mole beyond the theoretical
amount required for the alkali which will be bound chemically in the ethoxide . Having less than 10% molar
excess of alkali hydroxide , the equilibrium for the reaction
will drift back towards the left . This small amount of
10% excess beyond the theoretical requirement is very pertinent to my " making the leap " in proposing that
this reaction shouldn't require any column at all , and
should proceed in a similar way as a batch process
although the minimum excess of theory might be tripled
without a column , to keep the time of reaction reasonably short .
Concerning the hydrates of alkali hydroxides which you have mentioned , I had already thought about the possibility of a series of such possible
hydrates which are formed from evaporation from hot melts being concentrated , where in *liquid* form there well may
be a stepwise dehydration marking distinct hydrates ,
which have identifiable melting/solidification points as
distinct hydrates . But those distinct stages of hydration
would only come into consideration for the entire mass in
the molten condition , and have no bearing for the dessicant properties of the material after it has cooled and solidified . After solidification ,
the absorptive properties of the *solid* are virtually gone with regards to any practical reaction rates and the solid does not
behave the same as would say for example a liquid
hydrate of sulfuric acid , which as a liquid is free to
seek different levels of hydration for the mass ,
as if swelling like a sponge . When you have the
hydration status of a melt * locked * in place upon
solidification and cooling which effectively seals the
interior of the solid from exposure to external moisture ,
then its dessicant properties is not absorptive en masse
but is shifted by the physical limitation of the solid to
become a surface reaction manifested by deliquesence ,
forming an aqueous solution as a film wetting the surface
of a structure beneath which does not change , but
is like an ice cube sitting in liquid water so cold that
the ice cube does not melt further nor further freeze
until the properties of the liquid in contact is changed .
When handling solid prilled alkali hydroxides , you may notice that when the " dry " solid granular material
is exposed to the humidity of the air , during weighing operations for example , it does not gradually swell in volume as a still solid material
passing through stages of higher and higher yet still solid hydrates and then sudddenly liquify en masse . But what does happen is an almost instant
formation of a film of liquid on the surface of the prills which makes them adhere to each other .
Even if it is aknowledged that different stages of dehydration do occur in a melt which is being concentrated at higher and higher temperatures of
fusion , this does not necessarily mean that the
reverse sequence of rehydration occurs in like stages
for the cooled and solidified melt exposed to moisture
upon its surface . It is not the same case or mechanism
as would be for a porous silica gel which physically
absorbs water . Nor is it the same case as for a
porous material like drierite , or for a liquid dessicant
like sulfuric acid . A deliquescent material operates
according to a distinctly different process .
Many of the deliquescent nitrates behave exactly the same way , calcium nitrate and magnesium nitrate are
two which come to mind .
Anyway , for the 10% molar excess to be the lower limit
for driving this reaction *completely * to the right , in a vertical columnar reaction zone having a 24:1 height to diameter ratio in ( inches ) for
the reactant is a very mild
contrast of conditions , in my opinion , over what would be the effect in a " one pot " batch reaction , compensating for any absence of the reaction
zone gradient which may be the benefit of the column simply by using a greater excess of solid alkali hydroxide in the one pot process .
As an integral part of my contemplated one pot variation , what I had fully intended was to add a fair amount of toluene to the ethanol solution over
dissolving and excess undissolved solid hydroxide , *during* the boil , lettting the added effect of the azeotropic
dehydration augment the dessicant property of the alkali hydroxide , and shorten the time required as well as
produce an even more complete conversion .
Rosco's good old country recipe for sodium ethoxide
would marry the salting out effect of Organikums column reactor with the concurrent azeotropic removal of water applied as the " kicker " to eliminate
the entire issue of debate concerning the column .
Anybody got a ternary mixture data chart handy for
toluene /ethanol/ water ?
Basically all you would need to do is place your weighed
quantity of NaOH prills and a stirbar into a stoppered flask with the measured amount of ethanol , bring it
up to a boil until you have a saturated solution over
the excess of undissolved solid NaOH . Allow the mixture to cool down a bit and add your toluene . Return the mixture to a boil and let it sit there
boiling away like a whistling teakettle . There would probably be so little
of this added azeotropic removal of water needed that
on a lab scale it would be sacrificial solvent loss here ,
and little point in using a reflux condenser , water trap
and solvent return as would be used for economy with
large batches .
There could be worked out some optimum proportions
which would make this straightforward , and a standard
method .
The only point of uncertainty about this proposed method
is whether or not separation of the phases might have to be done before adding the toluene for the Azeotroping , and
if any fresh sodium hydroxide being added with the toluene
might also be beneficial to the yield from that point .
CRC lists the ternary azeotrope : bp 74.4
ethanol 37
toluene 51
water 12
The boiling point with decreasing water
should gradually rise towards the binary azeotrope: bp76.7
ethanol 68
toluene 32
Absent any toluene ,
The ethanol water binary azeotrope : bp 78.2
ethanol 95.6
water 4.4
And for pure ethanol the bp is 78.5 C .
It may be practical to follow the course of the reaction
simply by watching a thermometer observing for the cessation of gradual elevation in boiling point and the appearance of precipitated solid sodium
ethoxide as the solvent is boiled away . At this point the product
is available as its saturated solution in the supernatant ethanol .
[Edited on 4-9-2006 by Rosco Bodine]
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hinz
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I've just tried to make aluminium isopropylate or Al isopropoxide and it works quite nice without CCl4 or CHCl3, only with HgCl2 and some iodine. I
cooked it originally just for fun to get the reagent for the Meerwein-Ponndorf reaction, but it works that nice that it would be probalbly also
possible to get sodium ethoxide from it, if you exchange isopropanol by ehanol. Like:
Al(OEt)3 + NaOH ==> NaOEt + Al(OH)3
AlOH3 is insolule, so the reaction is quantitive
For Al(OIpr)3:
I took Al foil and Al turnings put it in a 2l RBF and added 1,3l isopropanol and a few grams of I2. I heated it, but nothing happened, so I added a
bit NaOH , I thought it could complex the oxide layer, but nothing happened too, so I took my last bit of HgCl2, made from a small mercury switch, it
was something like 0,25-0,5g and added this and the reaction worked quite vigorous. I could place my hand on the top end of the condensor and felt the
pressure of the hydrogen evolved.
The isopropanol was technical, 95% or so.
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trilobite
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After reading the thread alcoholic KOH & experiment suggestions I remembered that there were some reasons to revive this topic. Usually it is assumed that ethoxide is
a stronger base than hydroxide. Needless to say, properties of the solvent affect the properties of a solute, so one should be careful when making
conclusions based on measurements in one solvent only. I still managed to find the reference that says that ethoxide is the weaker base in ethanol,
while the opposite is true in water. While the conclusion is based on extrapolation it makes a good argument. I didn't bother to get the article from
the library and scan it, but luckily the abstract is like they used to be.
<b>The equilibrium between ethoxide and hydroxide ions in ethanol and in ethanol-water mixtures.</b>
Caldin, E. F.; Long, G.
Journal of the Chemical Society, , 3737-42 (1954).
CAN 49:18704 ISSN 0368-1769
<u>Abstract</u>
Equil. consts. (K') for the reaction, OEt- + H2O = EtOH + OH-, in EtOH and in EtOH-H2O mixts. were detd. by use of a colorimetric method. The
indicator was 2,4,6-trinitrotoluene, which ionizes in EtOH in the presence of a strong base to give a purple soln. K' is defined as [OH-]aa/[OEt-]aw,
where brackets indicate molar concns. and aw and aa are activities of H2O and alc. with respect to the pure liqs. K' varied between 1.0 and 3.1 for
solns. contg. between 12.6 and 47.0% H2O. Extrapolation of the values gave K' = 0.5 for pure EtOH, in good agreement with the results of Hine and
Hine (C.A. 47, 1473a) for iso-PrOH. It is concluded that solns. of alkali hydroxides in EtOH contain mostly OEt- ions rather than OH-. Thus, in 0.1M
solns. of NaOH in 100 and 99% EtOH the total base present as OEt- is 99.2 and 95.9%, resp. Similar conclusions can be made for MeOH solns. Solns.
made by dissolving Na in EtOH contg. a small amt. of H2O also contain mainly OEt- rather than OH- ions; only a small fraction of the H2O is removed by
this means. The values of K' furnish an approx. measure of the relative acid dissocn. consts. of H2O and EtOH. In the solvent EtOH, H2O is a
somewhat weaker acid than EtOH, whereas in the solvent H2O, EtOH is weaker.
The problem with using toluene azeotropes is, according to literature, that it takes a lot of time and a good column to drive the reaction to
completion. For us the heat economy may not be such a big issue as for the industrialists but reliability is. You'd either have to analyze your
product or have a really consistent method. Following water evolution isn't going to help much when you are distilling it with ethanol and toluene.
There are some situations where it is desirable to have as little water present as possible. For example, to avoid the use of diethyl malonate one can
prepare organic acids by alkylating ethyl acetoacetate in the traditional way. The product is then boiled with NaOH in ethanol (called acid hydrolysis
because the product is an acid). Much better yields are achieved if the reaction is performed with EtONa in ethanol, distilling off the ethyl acetate
that forms in the reaction as ethanol azeotrope. The outcome pretty much depends on how little water you have in the mixture, and if I recall
correctly, the problem is worse with single-alkylated than double-alkylated acetoacetates. To my knowledge the copper-catalyzed conversion of
bromobenzenes to methoxybenzenes with MeONa doesn't like water either, but that's a different story as you cannot use EtONa in the same way, and I
think you cannot use toluene for making the MeONa either.
Here's an abstract of a study of EtONa production with azeotropic distillation with benzene. I think the interesting parts are their method for
estimating the completion of the reaction, also the boiling points and yield.
<b>The application of a fractional distillation method in the preparation of sodium ethoxide from caustic soda.</b>
Walker, T. Kennedy.
Journal of the Society of Chemical Industry, London, 40, 172-3T (1921).
CAN 15:19359 ISSN 0368-4075
<u>Abstract</u>
EtOH, H2O, and C6H6 form a const. boiling ternary mixt., and with a perfect stillhead any sample of moist EtOH could theoretically be dehydrated by
distn. with C6H6 (Young, J. Chem. Soc. 81, 707(1902)). W. employed this method to remove the water from the system NaOH + EtOH <=> NaOEt + H2O.
The chief difficulty in the sepn. lies in the fact that the b. p. of the ternary mixt. is only a few degrees lower than that of the binary mixt. of
EtOH and C6H6 or of the pure substances; complete conversion of the NaOH cannot be expected since the effective proportion of volatile matter toward
the end of the process is small. The proportion of EtONa formed was detd. as follows: 10 cc. of liquid were titrated with 0.1 N HCl to det. the total
alkali (NaOH + EtONa). Another sample of 10 cc. was boiled with 12.5 cc. AcOEt and 50 cc. EtOH, when the following reaction took place: xNaOH + yEtOH
+ zH2O + wEtONa + uAcOEt = (x + z) AcONa + (w - z) EtONa + (u - x - z) AcOEt + (y +x + 2z) EtOH. The whole was then titrated with standard benzoic
acid in EtOH. A diminution in alkalinity was thus observed as compared with the previous titration against 0.1 N alkali; this diminution in alkali
gave (x + z), the max. quantity of H2O that would be obtained by evapg. 10 cc. of alk. fluid from the still to dryness without loss of water. The
total alkali gives (x + w), while (w - z) was the minimum quantity of EtONa to be obtained by evapg. to dryness. The number 100 (w - z)/(x + w) is
the "mol. percentage yield" of EtONa. Blanks indicated that the method gave results 4% low. The C6H6 used was purified, dried, and redistd.
Anhydrous EtOH was prepd. from com. 96% alc, by dehydration with CaO and metallic Ca. The solns. before distn. were made up by mixing weighed
quantities of EtOH, Na, and H2O. Preliminary expts., in which the distn. was carried out through a Vigreaux column 40 in. long and 0.75 in. in diam.,
gave a 25% yield, which by redistn. with fresh alc. and C6H6 was raised to 28.1%. By distn. through a Dufton stillhead (C. A. 13, 917) 1.5 m. long
with an annular space 1.5 mm. wide, the yield was increased to 33.8%. About a 57% yield was obtained with a column 6 ft. high and 1.6 in. in diam.,
filled with 4000 Raschig rings of sheet iron; 40 g. NaOH (23 g. Na and 18 g. H2O), 1012 g. alc., and 600 g. C6H6 were distd. at 1 drop per sec.; 149
g.distd. over up to 66.55 Deg; the distn. was stopped at 68.2 Deg, leaving a flask residue of 785 cc. Analysis of this residue showed a 54.2% yield,
while from the quantity of ternary mixt. obtained the value 61.2% was found.
Here are some patents on alkoxides and dehydration of alcohols, some of them are mentioned already in this thread. The dichloromethane-water azeotrope
used to dehydrate allyl alcohol is often overlooked as OTC substitute for carbon tetrachloride.
GB304585 BuOH + NaOH -> BuONa
US1681600 ethylene glycol + NaOH -> Na-glycolyloxides
US1712830 EtONa by azeotropic distillation with benzene
US1816843 aka GB334388 EtOH + NaOH in paraffin oil
US1907834 drying of ethanol with Na-glycolyloxides
US1910331 aka GB377631 EtONa by extractive distillation with benzene
US2179059 dehydration of allyl alcohol by H2O-DCM azeotrope
US2278550 miscellaneous alkoxides
GB698282 and DE628023 MeONa by distillation of methanol with NaOH, recirculation of methanol
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LSD25
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| Quote: | Originally posted by Organikum
A sep-funnel or anything else with an outlet (faucet) at the bottom is filled to 1/3rd with NaOH pellets and filled full with EtOH of 92% or of higher
concentration (preferred). This sits for at least half an hour and then about 1/4th of the liquid at the bottom is withdraw very slowly. Then the rest
is withdraw. This rest consists of EtOH which contains sodium ethoxide. Distilled to yield anhydrous EtOH, sodium ethoxide is left back which can be
used to dry more EtOH so desired.
If the alcohol is pre-dried with anhydrous CuSO4 which was dehydrated at 300°C+ much less NaOH is needed. This pre-drying takes time though, the
longer the better in special if no stirring is applied.
If the ethoxide is whats desired the alcohol should be left in the vessel for longer time, if bigger amounts are wanted it is favorable to withdraw
alcohol/ethoxide from top and water/NaOH/alc from bottom and to refill alcohol. This is an almost continous process then.
Tried and true. |
Yup, and if someone who has access to 'Nature Journal' could get this letter and if possible to follow the research trail it starts, we may even have
some proof to support Organikum's suggestion:
Caldin & Long, Equilibrium between Ethoxide and Hydroxide Ions in Ethanol, Letters to Nature, Nature 172, 583-584 (26 September 1953) |
doi:10.1038/172583b0: http://www.nature.com/nature/journal/v172/n4378/pdf/172583b0...
It is not that I doubt Org, it is simply that I would like to know how this works and what sort of yield one could expect.
Whhhoooppps, that sure didn't work
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solo
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Reference Information
The Equilibrium between Ethoxide and Hydroxide Ions in Ethanol
and in Ethanol- Water Mixtures.
E. F. CALDIN and G. LONG.
J. Chem. Soc, 1954. 4, pp.3737
Abstract
The equilibrium constant for the reaction
OEt- + H, OSEt OH + OH-
in ethanol-water at 25" has been determined. In mixtures containing a few
per cent. of water, and in pure ethanol, the equilibrium favours ethoxide ion.
It is deduced that solutions made by dissolving alkali hydroxides in ethanol
will contain mainly ethoxide ion rather than hydroxide. For instance, in a
0-lM-solution of sodium hydroxide in 99% ethanol, 96% of the total base is
ethoxide. Solutions made by dissolving sodium in ethanol or aqueous
ethanol are also considered. The relative acid dissociation constants of
ethanol and water, in (a) ethanol, and (b) water, are estimated; in each
solvent they differ by less than a power of 10.
Note: the Nature citation is also included here for comparison,
http://mihd.net/nkluf2
Attachment: Equilibrium between Ethoxide and Hydroxide Ions in Ethanol.pdf (1.2MB)
This file has been downloaded 2539 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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LSD25
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That first article kicks shit out of the Nature letter.
Thanks Solo
Perhaps, given the importance of Sauron to this forum, it is time to shift this stuff over to WD? I mean, I ain't allowed to irritate the fuck and
much of my contribution irritates it. QED, the majority of my contributions are not welcome on this site.
PS This fits in well with the suggestion made elsewhere too, don't it?
[Edited on 24-2-2008 by LSD25]
Whhhoooppps, that sure didn't work
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Siddy
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Ok, so practically when 1/3rd of a sep funnel is filled with NaOH anhydrous pellet and then the rest of the fulled is filled with 95% EtOH (with the
remaining 5% MeOH and Water), the HIGH majority of NaOH does not dissolve.
Is this correct? Or should the NaOH all dissolve?
Has anyone tested to see if the 3/4 that supposedly cotains EtOH, Na(+) and (-)OEt is actually water free?
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The_Davster
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| Quote: | Originally posted by Siddy
Has anyone tested to see if the 3/4 that supposedly cotains EtOH, Na(+) and (-)OEt is actually water free? |
Any water will react with ethoxide producing more hydroxide.
It is impossible for it to contain water.
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Siddy
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| Quote: | Originally posted by The_Davster
Any water will react with ethoxide producing more hydroxide.
It is impossible for it to contain water. |
Can that be used to test if it is water free?
Ie, if water is added to the proposed EtOH and Ethoxide, will a notable reaction take place? Will the pH lower?
Are there any other methods for testing? I thought of adding CaCl2 chips but they will dissolve in alcohol just as well as water...
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