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Keras
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Quote: Originally posted by Jenks  | | Phosphoric acid seems to be the obvious alternative to prevent reduction of the acid from being a problem. |
I already tried 75% phosphoric acid, but ethanol just boils unchanged from it.
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Jenks
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I'm surprised. This is useful to know. Maybe the dehydrating ability of sulfuric acid is driving the reaction. But Diachrynic wrote, "It can also be
seen that the dilution of water is not limiting the reaction, as it distills off alongside the ether and alcohol in more or less a stable equilibrium,
if it is allowed to do so." If the water is removed by distilling it as the azeotrope, the sulfuric acid is not needed for this. Maybe the ester
intermediates are the key, and the mechanism is not as simple as protonation of ethanol.
[Edited on 20-5-2024 by Jenks]
[Edited on 20-5-2024 by Jenks]
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Keras
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| Quote: Originally posted by Jenks |
I'm surprised. This is useful to know. Maybe the dehydrating ability of sulfuric acid is driving the reaction. But Diachrynic wrote, "It can also be
seen that the dilution of water is not limiting the reaction, as it distills off alongside the ether and alcohol in more or less a stable equilibrium,
if it is allowed to do so." If the water is removed by distilling it as the azeotrope, the sulfuric acid is not needed for this. Maybe the ester
intermediates are the key, and the mechanism is not as simple as protonation of ethanol. |
Yeah, there is obviously something specific about sulphuric acid.
I will try again in the following days and keep you posted.
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bnull
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| Quote: Originally posted by Jenks | | If the water is removed by distilling it as the azeotrope, the sulfuric acid is not needed for this. Maybe the ester intermediates are the key, and
the mechanism is not as simple as protonation of ethanol. |
Protonation of ethanol is the crucial step (see, for example, https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Or...); otherwise there is no reaction. Sulfuric acid is needed because it is a strong
acid and consequently a good proton donor, and is also non-volatile. Other common strong acids (HCl, HNO3) are volatile and boil off well
before the reaction temperature. Phosphoric acid is fixed but weak.
There are no ester intermediates. If that were indeed the case, phosphoric acid would work. Even boric acid would do.
[Edited on 20-5-2024 by bnull]
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chornedsnorkack
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Indeed. Compare the boiling point of 85% phosphoric and 85% sulphuric acid. They have the same molar mass - both are 50% by mole. The boiling point of
85% H3PO4 is quoted as 158 degrees - cannot quickly find a quote for 85% H2SO4 boiling point but from
graphs looks around 215 degrees. Equimolar amount of sulphuric acid protonates water much more fully that phosphoric acid.
Strong monobasic acids like HClO4, CF3SO3H, ClSO3H and FSO3H are more volatile themselves
because they have less bonds for hydrogen bond network. (And ClSO3H and FSO3H hydrolyze in water anyway). The one acid whose
strength is close (slightly lower) and volatility similarly small is H2SeO4, and it is more oxidizing.
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RU_KLO
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I want to test the ether "pipe" procedure.
This is the main idea:
For this Im going to use a 1 inch threaded gas pipe (its used for Home gas instalation)
(check picture)
96º EtOH + Fe2SO4 will be poured inside the pipe, screwed (with teflon tape).
An then put in a oil bath at 150ºC (it will be put at ambient temperature and then heated)
after 8 hours, it will be removed from the bath, cooled (ice water), filtered and meassured.
Now the problems:
(I dont want to have a solvent granade in hot oil....)
1) the pipe:
I meassured 1mm thickness at the thread root. (from the rust I think they are made of iron, but regulations states: it should be form steel and test
are 50 bars at room temp for 5 s. and for 1 inch pipe, thickness 2.9mm)
The thread is another problem. Checked without teflon tape (for volume with water) and it was like a wathering can.
From what I read Teflon will hold on 150C. Also maybe I will use high temp silicon seal (up to 240ºC)
Could the pressure be calculated? 150ºC + 70 ml EtOH (some converted to ether - lets hope - maybe some ethylene
Here Im in a field I dont know, so if mistakes are made, please correct.
form this calculator:
http://ddbonline.ddbst.com/AntoineCalculation/AntoineCalcula...
Temperature [°C] Pressure(1) [mmHg] Pressure(2) [mmHg]
150 T > Tmax 7355.67
from google:
7355 mmHg -> 9.8 Bar
so if this should pass a 50 bar test (although 5 s), I think its safe.
Will it hold?
If there is a leak because bubbles are seen from the thread.(because of pressure)
How will react ether/ethanol gas to 150C vegetable oil? (ignite? boil off? dissolve?)
Does someone could share broken glassware - high flamable solvent(if ether better) - oil bath experience, to expect the worst?
How it is mitigated?
thanks
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bnull
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| Quote: Originally posted by RU_KLO | I want to test the ether "pipe" procedure.
This is the main idea:
For this Im going to use a 1 inch threaded gas pipe (its used for Home gas instalation)
(check picture)
96º EtOH + Fe2SO4 will be poured inside the pipe, screwed (with teflon tape).
An then put in a oil bath at 150ºC (it will be put at ambient temperature and then heated)
after 8 hours, it will be removed from the bath, cooled (ice water), filtered and meassured. |
Good Lord! I'm glad you asked before proceeding. Ferric sulfate (Fe2(SO4)3) will corrode the steel pipe. The
reaction, as far as I can see, is $$Fe_2(SO_4)_3+Fe^0\rightarrow3FeSO_4.$$ There's a big chance the threads will corrode from the inside to the end
and you know what happens. Also, the sealed or closed tube is a glass tube with thick walls into which the substances are poured and the open
end is sealed in the same manner as an ampoule. Then the tube is put inside a steel pipe or something similar to contain an eventual explosion.
Consult references on the sealed tube or Carius tube or the pipe bomb technique before actually trying. It seems there are plenty in the old books in
the Library; selaed tube techniques are older than Quantum Physics.
As I wrote somewhere else, you can always buy new equipment but can't buy new fingers. I may be--and probably am--overestimating the risks. But safety
is safety.
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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RU_KLO
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| Quote: Originally posted by bnull |
Good Lord! I'm glad you asked before proceeding. Ferric sulfate (Fe2(SO4)3) will corrode the steel pipe.
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Do you think that 10 gr Fe2(SO4)3 in 70ml EtOH will make a hole (or compromise seal) in a 1mm steel pipe 8hs 150C?
Go SAFE, because stupidity and bad Luck exist.
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bnull
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Yep.
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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Keras
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So I decided to give a go at the standard procedure using a less concentrated sulphuric acid. I took a bottle of 37% battery sulphuric acid, distilled
it at the max temp. of my hot plate/stirrer (280 °C, but I suppose the liquid was not that hot), got about half the water out. So that should’ve
left me with 74% acid. Let's say 65% is more reasonable.
I used that ~ 15 mL to try get ether from 10 mL of ethanol. Definitely I got ether, judging by the smell. But the distillation took forever and what I
collected was ether in water, not water in ether. Nothing useable. Re-distillation of the product yielded nothing, no 36 °C perceptible stop, barely
a small notch around 50 °C.
So, what seems to happen when you don’t use concentrated acid able to pull out water from the mix is that you have to face Le Châtelier's law.
Since ether creation also makes one molecule of water, any water present drives the reaction backwards. Concentrated sulphuric acid both serves as a
source of proton for protonating ethanol AND as a water absorbant. Once its dehydrating properties are lost (~85% ???) the reaction is much less
vigorous.
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Rainwater
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When doing the pipe bomb method with other experiments i install a small brazed tube with lots of length, . I like the 1/8ID soft copper tubing.
Connected to one of the caps, it allows you to have a pressure gauge and valve to collect products and monitor the reaction.
Forming a gas product inside a sealed reaction vessel makes a positive feedback loop,
increase in pressure, which increases temperature, which increases reaction speed, which increases pressure which goes boom. This process can also be
illegal in some states without a license and the reactor may also require state certification. A 1in tube can pack a serious punch, you may wish to
start on a smaller scale. The conversion from liquid water to steam will be in the ball park of 1mlliquid = 1700mlgas not sure
how to calculate what your numbers will be, google the ideal gas laws if you want to figure out the pressure. It will be a lot.
Once you have accurate numbers, factor in a 80-120% safety margin and you can safely build a reactor.
Edit:
If all else fails, do your experiments in a hole in the ground. Ensure it is deep enough so the top of your appratus forms an angle of inclination
that will limit the fallout to an acceptable area.
[Edited on 23-5-2024 by Rainwater]
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clearly_not_atara
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If you want to use a phosphoric-based catalyst for this rxn you should dehydrate the phosphoric acid to polyphosphoric acid first and then add
ethanol, clearly 85% H3PO4 will not work but 100% H4P2O7 just might.
ding ding ding
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Keras
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I’ll try to make 100% phosphoric acid with, say, 25 mL of my 75% bottle and add phosphorus pentoxide.
If I’m not mistaken: 3 H₂O + P₂O₅ → 2 H₃PO₄.
So, d = 1.58. 25 mL are therefore ca. 40 g. So 10 g of water, M = 18, 0.67 mol / 3 = 0.222 mol of phosphorus pentoxide, M = 142 g/mol, that makes 31.5
g.
Still quite a lot into a measly 25 mL.
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clearly_not_atara
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| Quote: Originally posted by Keras | I’ll try to make 100% phosphoric acid with, say, 25 mL of my 75% bottle and add phosphorus pentoxide.
If I’m not mistaken: 3 H₂O + P₂O₅ → 2 H₃PO₄.
So, d = 1.58. 25 mL are therefore ca. 40 g. So 10 g of water, M = 18, 0.67 mol / 3 = 0.222 mol of phosphorus pentoxide, M = 142 g/mol, that makes 31.5
g.
Still quite a lot into a measly 25 mL.
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I don't think this will be nearly strong enough! The diphosphoric acid H4P2O7 is an interesting reference point because it forms a pure crystal with a
relatively high mp while solutions of polyphosphoric acids which are more or less concentrated tend to form thick gels at rt. Pure H3PO4 essentially
does not exist; it disproportionates into a mixture of water, phosphoric acid and polyphosphoric acids (though the majority of this solution is
H3PO4). 85% is the highest concentration of H3PO4 which can be achieved that does not contain significant amounts of H4P2O7. See e.g.:
https://pubs.acs.org/doi/pdf/10.1021/i260053a014
"high-purity, crystalline, free-flowing pyrophosphoric acid" sounds much nicer than the usual sticky crap
[Edited on 23-5-2024 by clearly_not_atara]
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chornedsnorkack
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| Quote: Originally posted by clearly_not_atara | | Quote: Originally posted by Keras | I’ll try to make 100% phosphoric acid with, say, 25 mL of my 75% bottle and add phosphorus pentoxide.
If I’m not mistaken: 3 H₂O + P₂O₅ → 2 H₃PO₄.
So, d = 1.58. 25 mL are therefore ca. 40 g. So 10 g of water, M = 18, 0.67 mol / 3 = 0.222 mol of phosphorus pentoxide, M = 142 g/mol, that makes 31.5
g.
Still quite a lot into a measly 25 mL.
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I don't think this will be nearly strong enough! The diphosphoric acid H4P2O7 is an interesting reference point because it forms a pure crystal with a
relatively high mp while solutions of polyphosphoric acids which are more or less concentrated tend to form thick gels at rt. Pure H3PO4 essentially
does not exist; it disproportionates into a mixture of water, phosphoric acid and polyphosphoric acids (though the majority of this solution is
H3PO4). 85% is the highest concentration of H3PO4 which can be achieved that does not contain significant amounts of H4P2O7. See e.g.:
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I gather that pure H3PO4 does exist, because the disproportionation you mention is kinetically slow. This is why
H3PO4, like S, has two melting points, too...
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clearly_not_atara
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I see you've put in time in the Central Bureaucracy 
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Mateo_swe
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According to the included paper alcohol + anhydrous ferric sulphate is most effective with a yield of 75% of ether.
"Three cm3 alcohol and 13 cm3 ether were obtained from 4 g ferric sulphate and 20 cm3 alcohol (96 %). The yield was 75 %."
Its an old but intresting paper.
Only problem is the procedure,
"the reaction mixture was heated for eight hours in a closed tube in a Carius oven at a temperature of
155°C- 160°C. When cooled down, the tube was opened, the mixture fractionated by means of a Vigreux column."
Will this work in a non closed vessel like ordinary glassware with reflux condenser?
Attachment: J. van Alphen - The formation of ether from alcohol.pdf (428kB)
This file has been downloaded 130 times
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Rainwater
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Likely but controlling the losses do to evaporation will be harder, the difference in pressure will have an effect of the reaction kinetics.
A simple pressure estimate for a closed vessel.
Couldnt find a one stop source for these values https://www.engineeringtoolbox.com/
Ethanol at 160c 10-15bar or 217psi
https://en.m.wikipedia.org/wiki/Diethyl_ether_(data_page)
Diethyl ether @ 156c 15200 mmHg or 295psi
So the regular black steel pipe will hold that pressure at that temperature(7500psi 1" sch 40). But as you noted before the caps are the weak point. A
welded fitting would exceed the pipe rating.
A threaded fitting, standard at best will be 300psi at room temperature, then downgraded 5% per 10c so your looking at
150c-30c = 120
Every 10 degrees derate 5%, so thats 12 derateings
So 300start pressure * (0.95derated factor^(12# of deratings)) drum roll.... 162psi before applying a safety factor
which would knock it down to abou 130psi.
Im going to go ahead and say this can not be safelydone with standard fittings from the hardware store. You can order high pressure/tempature
fittings what will easily handle 1000+psi. They cost about 4x as much, but for a simple 1in reactor your looking at $40 + S&H
[Edited on 24-5-2024 by Rainwater]
"You can't do that" - challenge accepted
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RU_KLO
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| Quote: Originally posted by Rainwater |
Likely but controlling the losses do to evaporation will be harder, the difference in pressure will have an effect of the reaction kinetics.
A simple pressure estimate for a closed vessel.
Couldnt find a one stop source for these values https://www.engineeringtoolbox.com/
Ethanol at 160c 10-15bar or 217psi
https://en.m.wikipedia.org/wiki/Diethyl_ether_(data_page)
Diethyl ether @ 156c 15200 mmHg or 295psi
So the regular black steel pipe will hold that pressure at that temperature(7500psi 1" sch 40). But as you noted before the caps are the weak point. A
welded fitting would exceed the pipe rating.
A threaded fitting, standard at best will be 300psi at room temperature, then downgraded 5% per 10c so your looking at
150c-30c = 120
Every 10 degrees derate 5%, so thats 12 derateings
So 300start pressure * (0.95derated factor^(12# of deratings)) drum roll.... 162psi before applying a safety factor
which would knock it down to abou 130psi.
Im going to go ahead and say this can not be safelydone with standard fittings from the hardware store. You can order high pressure/tempature
fittings what will easily handle 1000+psi. They cost about 4x as much, but for a simple 1in reactor your looking at $40 + S&H
[Edited on 24-5-2024 by Rainwater] |
What about a CO2 Fire extinguisher tube?
"CO2 gas is held in the fire extinguisher under pressure, normally around 55 bars at room temperature." (i.e: 797.708 Psi)
NFPA 10 :
"8.6.3.2 Dry chemical, dty powder, water, foam, and halogenated
agent discharge hose assemblies requiring a hydrostatic
pressure test shall be tested at 300 psi (2068 kPa) or at service
pressure, whichever is higher.
8.6.3.3 Low-pressure accessor·y hose used on wheeled extinguishers
shall be tested at 300 psi (2068 kPa) .
8.6.3.4 High-pressure accessory hose used on wheeled extinguishers
shall be tested at 3000 psi (20.68 MPa).
"
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RU_KLO
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recovering H2SO4 from Diethyl ether making.
It there a possibility to get/recover any usable H2SO4 from the "tar" of an classic H2SO4 - ethanol ether syntesis?
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unionised
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Can I just check?
Are you planning to cause a bang by allowing the ferric sulphate to attack the steel of the fire extinguisher?
There also seemed to be some talk of using pyrophosphoric acid, which not only (probably) won't work but attacks steel and glass and, for extra fun...
... makes the nerve as substitute tetraethyl pyrophosphate.
I suspect the yield would be bad.
But not bad enough.
https://en.wikipedia.org/wiki/Tetraethyl_pyrophosphate
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BAV Chem
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Making ether using phosphoric acid is actually possible and i did that at one point. This was more than 3 years ago so I don't remember everything.
Also I didn't write anything down back then so the following might not be the complete truth.
The acid I used back then was mostly polyphosphoric acids that I made by boiling it down as far as i could using my heating mantle (yes, I etched the
flask a couple times). Making ether with that stuff doesn't work very well though. It starts out by first boiling off a bunch of ethanol which is
probably because phosphoric acid doesn't have nearly as great an affinity for ethanol as sulfuric acid would. Somewhere at or above 140C (if memory
serves) there was some ether produced but this didn't last long before all the ethanol was gone. On addition of more ethanol the mix boiled and
splashed violently and most of the enthanol just distilled off. Pretty soon the production of ether was very slow and I think this was because most of
the polyphosphoric acid was already hydrolyzed to a critical degree. Upon heating the mix way beyond 150C a whole load of ethylene was generated and
the acid slowly lost its water again. After that point I think I tried adding more ethanol and doing the reaction at 140C as before and that did
afford some more ether but the total yield was still terrible. I ran something like 500ml of ethanol through it and probably spent two days on it and
got around 50ml of ether. I likely made more ethylene than ether and all in all it absolutely sucked in comparison to using sulfuric acid.
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Keras
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I have just tried to produce ether with the 100% phosphoric acid I made by dissolving the stoichiometric quantity of phosphorus pentoxide into 75%
commercial phosphoric acid and I got exactly the same thing (picture). Most of what distills above 140+ (nothing does under) is ethanol, at ~75 °C.
There is definitely ether, because the ethanol strongly smells of it. But when I’m redistilling the product (which I’m currently doing),
everything passes at 75 °C+. Probably phosphoric acid doesn’t bind with ethanol, or something of the same ilk. It was promising though, because
when I added an initial 5 mL of ethanol into the 5 mL of phosphoric acid, the solution warmed up. The phosphoric acid remained clear all along, there
is no charring or tar like what we get with sulphuric acid (second picture).
I'd say that what is left after redistillation (I cut at 80 °C) is… smelling like pure ether, except it can’t be. I got strictly nothing at 36
°C, the solution was not even boiling.
Is there any test I can carry out to identify the ether contents, apart from smelling?
PS: If I remember correctly, ether is industrially made by passing ethanol vapours over solid phosphoric acid. Very different conditions.
 
[Edited on 7-6-2024 by Keras]
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bnull
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What have we got so far
I thought it would be good to condense what has been discussed, what works and what does not.
Sulfuric acid is the classical catalyst, although it degrades and side reactions occur. The temperature must be right, around 140
°C; too low and either ethanol just boils off or the yield of ether is very poor; too high and you'll be losing ethanol as ethylene. Not to mention
The Tar.
The formation of ether using sulfuric acid starts with protonation of ethanol. It is the first and most crucial step. No esters are involved
since they appear because of the side reactions. Sulfuric acid is both a good protonator and a good dehydrating agent and that's why it works. Other
mechanisms are possible with other catalysts but, since we're dealing with sulfuric acid, protonation is still the first step.
Sulfuric acid is also fixed (non volatile), it doesn't distill along with the products.
Phosphoric acid and its cousins are fixed but not strong enough to be proposed as substitutes for sulfuric acid, and the yield is terrible.
Other stong acids are either volatile (HCl, HNO3) or good oxidisers (H2SeO4, HClO4), or both. You must
avoid the oxidisers at all costs because you're interested in ether, not aldehydes or carboxylic acids or "chemically-promoted relocation of lab
equipment".
The reaction may be carried out in sealed tubes, which are thick-walled glass tubes, other materials being attacked by hot acids. Other
substances work as catalysts, such as ferric sulfate (I guess I know why but I don't want to make an ass of myself again without a good reason). The
tubes are sealed because of the high pressures needed. A metal container, such as a capped pipe section or a fire extinguisher, will be
corroded; if you're lucky, the result is a sludge of iron oxides and sulfates in ethanol with perhaps a smidgen of ether inside a pitted container; if
you're out of luck, mayhem befalls.
The side reactions range from obnoxious (The Tar) to wasteful (ethylene) and, in the case of pyrophosphoric acid, TEPP and a wink from Fritz
Haber.
Am I missing something?
If we're to keep using sulfuric acid, so far the best catalyst in ether production, we'll need an additive. I list here some desirable characteristics
of the additive. It is not an exhaustive list. If someone else has any other characteristic to suggest, please do.
It must not react with ethanol, unless the product formed is in the pathway of ether formation.
It must be stable in the presence of hot sulfuric acid.
It must not react with sulfuric acid, unless the product is in the pathway of ether formation.
It must be fixed so we don't need to separate it from the distillate.
It must prevent or at least reduce the oxidation of ethanol by sulfuric acid.
It must not form volatile esters with ethanol.
It may be either solid or liquid. If liquid, it should be completely miscible; the reaction flask looking like a lava lamp could be a problem.
On the other hand, if we had two substances A and B which react with ethanol and among themselves, it could be a solution. Let's suppose that A reacts
with ethanol to form compound EtOA@, and B reacts with ethanol to form compound EtB$. If we then add EtOA@ to
EtB$, the products are ether and A@B$, being ether volatile and A@B$ fixed. A bonus would be if
we could regenerate A and B from the latter, perhaps by electrolysis or reactions involving less regulated reagents. A Williamson synthesis, for
example, uses sodium as A and a halogen as B. But it is more cumbersome and expensive (and probably dangerous) than simply boiling ethanol in sulfuric
acid. Again, if someone can suggest a pair (A, B) of substances, please do.
Quod scripsi, scripsi.
B. N. Ull
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RU_KLO
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| Quote: Originally posted by unionised | Can I just check?
Are you planning to cause a bang by allowing the ferric sulphate to attack the steel of the fire extinguisher?
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No, no. It was more like an "academic" question. After Bnulls post, understand it.
The problem is that I need some ether for inorganic analytical chemistry, and also concentrated sulfuric acid. Both regents are difficult to get in my
country, they are restricted, special costly permits, you need an chemical engineer to sign the papers, etc. (Of course concentrated sulfuric acid is
way more needed than ether.)
So any process for getting ether without sulfuric acid, is welcome.
On searching found that: Diethyl Ether and Sodium Chloride are formed when Sodium Ethoxide and Chloroethane react (Williamson Ether Synthesis)
Sodium Ethoxide: NaOH + ethanol
Chloroethane : HCl + ethanol
(Chloroethane: Toxic/flammable -
Chloroethane is produced by hydrochlorination of ethylene:
C2H4 + HCl → C2H5Cl
At various times in the past, chloroethane has also been produced from ethanol and hydrochloric acid, from ethane and chlorine, or from ethanol and
phosphorus trichloride, but these routes are no longer economical.
Is this route viable for amateur (or is very dangerous - more dangerous than ethanol sulfuric acid?
found this in the forum:
http://www.sciencemadness.org/talk/viewthread.php?tid=79850&...
From PrepChem, with references:
Preparation of ethyl chloride:
To the round bottom flask fitted with properly cooled reflux condenser and gas inlet 100 g of ethyl alcohol and 50 g of anhydrous zinc chloride are
placed. The top of reflux condenser is connected to two washing bottles. The first has water and the second concentrated sulfuric acid. Finally
apparatus is connected to a cooled flask for condensing the reaction product. A dry stream of hydrogen chloride gas is passed through the boiling
mixture. The vapors of ethyl chloride is washed with water, concentrated sulfuric and condensed in a flask which is cooled with freezing mixture of
ice and salt. As ethyl chloride boils at 12° C it must be kept in sealed glass tubes. The yield is almost quantitative.
Preparation of organic compounds, E. de. Barry Barnett, 71, 1912
So its not an easy task.... (instead of the second H2SO4 washing flask, sodium ethoxide would be used...)
[Edited on 7-6-2024 by RU_KLO]
Go SAFE, because stupidity and bad Luck exist.
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