| Pages:
1
2
3 |
len1
National Hazard
Posts: 595
Registered: 1-3-2007
Member Is Offline
Mood: NZ 1 (goal) - Italy 1 (dive)
|
|
Diethyl Ether - Illustrated Practical Guide
This is a series of Illustrated Key
Syntheses in Chemistry which I intend to post, with the purposes and guidelines outlined in the thread of the same name in the General Chemistry
section.
I shall attampt to ensure that the first post in all syntheses contains all the relevant information. If something needs to be added later on, due to
comments further down the thread for instance, I shall edit the first post.
Aim
It is the aim here to present an illustrated demonstration and comparison of two simple methods for generating and purifying diethyl ether suitable
for the amateur. The yield of the main product and impurities are analysed using analytical techniques and FTIR. A misconception associated with the
role of sulphuric acid in ether generation is illustrated, and this should allow to increase yield.
Motivation
Ether is a key compound in organic synthesis. Arguably the first anaesthetic used, nowadays its major use is as a solvent, a fuel, in extraction and
purification, and for anhydrous reactions such as Grignard synethesis. Its synthesis by H2SO4 catallytic dehydration of ethanol is described in many
organic practicums, however the yields and reaction rates are rather low - the combined volume of EtOH and H2SO4 produces 1/4 the volume of ether -
which brings into question its suitability as a preparative method for volumes required in the laboratory. An alternative source of ether easily
accessible to the amateur takes the form of fractioning of starting fluid, whose ether content ranges from 25 - 60%. There is a paucity of data on
the efficiency of this method, and the purity of the product so obtained, and this report presents a quantitative evaluation, and comparison to ether
obtained via the first method, for the least favourable 25% starter fluid. Some experimentation along these lines has already been presented in this
forum in the Making Diethyl Ether and Ethyl Ether Distillation and Synthesis threads. The present is an extention of these, with an improved
procedure, analysis, and illustrations.
Findings
The ethanol dehydration reaction is unsteady (non-smooth), time intensive, but is cheap, and can give good yields.
Yield 74% based on theoretical and 40% based on ethanol consumption
Ethanol based yield will tend to theoretical yield for larger runs
Reaction temperature of 140C is way above b.p. of EtOH leading to bumping
Instability, hard to establish correct EtOH drip rate and steady-state conditions
Almost all H2O formed distills with ether - minimum 4 purification steps required
12% EtOH distills unreacted - requiring corresponding amounts of CaCl2 for purification
Clear FTIR spectrum of product
Fractionation of starter fluid, is quick, efficient, product purity is comparable to the above - but it is expensive
76% yield of available ether using 25% ether starting mixture
Fast, single step procedure
H2O contamination evident in FTIR spectrum due to lack of purification - irrelevant for many extractions
Theory
Et-O-Et from dehydration of EtOH
C2H5OH + HHSO4 -> C2H5HSO4 + H2O
This is an acid base reaction in which sulphuric acid forms the ester ethyl bisulphate and generates water. This reaction occurs in the cold
immediately when the reagents are mixed, evolving much heat. For this reason its best to start with the reagents near freezing. This step forms the
main 'overhead' wastage of alcohol in this synthesis, since the alcohol remains bound and very little ether is generated. Note that H2O is generated
in this reaction in a 1:1 ratio to the H2SO4 used. Thus, contrary to what is often stated, one does not require absolute alcohol, or 98% acid for the
reaction to work. The main requirement is that the combined initial reagent water should not make the initial H2SO4 concentration less than about
70%, at which point the boiling point of the mixed acid approaches the reaction temperature used in step 2 - and it will start distilling over with
the products.
C2H5HSO4 + HOC2H5 -> C2H5OC2H5 + H2SO4
When excess EtOH is added to the mixture in (1) and heated to 140C ether if formed and H2SO4 regenerated - it thereby acts as a catalyst. If no
excess ethanol is added, the ethyl bisulphate remains stable to about 160C when it starts eliminating H2SO4 and generating ethylene C2H4. It is
therefore imperitive that this temperature is never reached during the reaction. Instead, ethanol is dripped in at the rate at which it is converted
to ether - two moles for every mole of ether formed, while the composition of the reagent fluid remains esentially that of (1). The H2SO4 liberated
regenerates ethyl bisulphate with the extra alcohol added.
The vapour pressure of water above 75% H2SO4 is about 0.4 atmosphere at the reaction temperature, hence it is distilled over with the ether as soon as
it is formed. Its concentration in (1) does not rise substantially during the reaction - the acid acts as a catalyst not as a dehydrating agent as is
often quoted. Therefore a little acid can produce quite a lot of ether - the limiting factor coming from oxidation-reduction side reactions, which
remove H2SO4 from solution, and result in the contents of the reagent flask becoming tarry.
Method
All reactions were carried out at an ambient temperature of 42C
Formation of crude ether
The first stage is to carry out reaction (1). 20gms of clean sand were placed at the bottom of a 1L 3-neck flask, and 180ml of EtOH (sold as
methylated spirit, about 95% EtOH) were poured in through a funnel. Next 160ml of 92% (1.81 sp) H2SO4 technical grade were measured out, and cooled,
together with the EtOH, in a freezer. The H2SO4 was then poured into the flask gradually and with frequent mixing - so the mixture attained
homogeneity before the next lot was added. This took about 5 mins, during which time the temperature of the mixture rose to about 60C. The flask was
fitted with a high-T thermometer, which dipped right to the sand, as well as an adaptor for measuring the exiting vapour temperature and an outlet
leading to a cooled-coil condenser. The vertial neck was fitted with a tube for delivering the EtOH right to the bottom of the reagent mixture,
Figure 1. This is necessary as the temperature at which ether is generated is well above the bp of EtOH. If dripped onto the surface of the reaction
mixture most will vapourise before reacting, introducing it below the surface affords better mixing - as evidenced by only 12% EtOH distilling
unreacted in the procedure. However the generation of superheated ethanol vapour is a major source of instability, and leads to difficulty in
controlling the reaction.
The receiver end is equiped with a secondary IR condenser, whose outlet dips through a delivery tube into an ice/water mixture, figure 2. The exit
from the delivery tube is vented. The secondary condenser is cooled by a small submerged 2.5W motor, circulating the freezing water through its
jacket. A secondary condenser is best employed to condense ether - which forms explosive mixtures with air - on hot days. Since the ambient
temperature in the lab was 42C (108F) ether would be a gas, and for the same reason tap water (30C) would not be efficient at condensing ether on such
a day. However a tap-water cooled condenser was used ahead of the ice-chilled stage to cool the 70C vapour from the reaction and extend the life of
the ice bath.
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs1_2.JPG">
Once the equipment had equilibrated, the mixture was heated on a heating mantle to about 140C, when some gas evolution (bubbling) commenced. At this
point 200ml EtOH was added to the drop-funnel and the delivery rate adjusted so the flow rate in the delivery tube was about 3mm/sec, at which rate
the entire volume is added in about 2 hrs. The delivery is accompanied by some unavoidable bumping due to the superheated ethanol, this periodically
shakes the reaction vessel contents, and introduces frothing, figure 3. The bumping can not be eliminated altogether, but it can be adjusted to
acceptable levels by keeping the EtOH delivery rate below the above mentioned, the rate can be gauged by bubbles in the delivery tube introduced by
the bumping. The temperature of the reaction bath stays at a remarkably steady 140-145C due to the thermal equilibrium introduced by the reaction -
the distilling ether and water removes heat which prevents the temperature rising. The temperature of the evolved ether/H2O vapour kept at a fairly
steady 60-70C. One can see the ether distilling with the water in the exit tube, figure 4.
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs3_4.JPG">
Reaction analysis
When all the EtOH had dripped into solution (~2hrs) the tap was closed and a temperature of 140C was maintained until the ether flow rate into the
receiving flask had curtailed (about 10mins). At this point the appartus was cooled down. The remnants in the reagent flask are seen in figure 5.
The black colour is due to oxidative side reactions producing carboneous mater, but there were no solid lumps, and the products of these reactions
were more obvious by appearance than by their volume.
The reaction mixture, 240ml, was titrated with NaOH solution and found to be 69% H2SO4 by weight. This represents a loss of 20gms H2SO4 - presumably
as SO2 in the oxidative reactions which produced the tar. The density of the reaction mixture was 1.48, compared to 1.46 for ethyl bisulphate and
1.58 for 69% H2SO4. Assuming a linear ethyl bisulphate/water density-concentration curve, we see that the remnant reaction mixture is mainly ethyl
bisulphate, with the water present 21gms, being essentially that of the initial acid. In addition the mass concentration of H2SO4 in the initial
ethyl bisulphate solution is 98/(98+46) = 68%. We thus come to the conclusion that the reagent mixture remained eseentially unchanged during the
reaction except for the loss of 21gms of H2SO4 to oxidation/reduction processes.
The main drawback of this reaction is the need to renew the spent H2SO4/EtOH reaction bath, which forms a waste in the process. The present findings
show that the reaction bath being mainly unchanged, is suitable for coninued use. The attrition, 21gms H2SO4 is a fraction of the 240gms H2SO4 still
remaining. It is likely the bath can be used for four-fold the volume of EtOH used in the present experiment (indeed this is consistent with the
finding of the inventor of the process - a little H2SO4 goes a long way). A further limiting factor is likely to be the build up of tar in the flask,
hindering the reaction.
Purification, yield
Figure 6 shows the contents of the receiver flask, 210 ml single layer. The content were poured into a separation funnel, 100ml of 10% NaOH solution
added, and shaken, figure 7. The aqueous layer was removed, and the process repeated. This left 182 ml ethereal product in the funnel, while the
aqueous layer correspondingly gained 28ml, where the second washing gained only 3ml showing this purification was essentially complete. Ether is 10%
soluble in water (presence of EtOH enhances this), and this washing removed mostly H2O (with SO2 and ethanol being minor impurities removed). This
result is in accord with the fact that 200ml of EtOH (3.4mol) produce 30gms of water according to reactions (1, 2) (recall that the initial 180ml
remained essentially unchanged).
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs5_6.JPG">
Next 26gms fused and crushed CaCl2 were placed in a flask, cooled, the ethereal layer poured in, and let to stand 1hr in the cold. The flask was then
placed in a water bath maintained at 60C, and the fraction boiling in the range 35-39C collected, figure 8. This left the flask almost entirely dry
- showing most water and ethanol have been removed by the washing and the CaCl2. The latter gained 18gms in the process, which is more than the
desired maximum 40% CaCl2 : EtOH ratio, hence we conclude 50gms fused CaCl2 per 200ml crude is the appropriate ratio in this setup. The adduct can be
seen in figure 9.
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs7_8.JPG">
The product was analysed on an FTIR machine (see the thread http://www.sciencemadness.org/talk/viewthread.php?tid=7993&a...) in both thick and thin film, and gave very good spectra, figure 10. The presence
of traces of H2O and EtOH are evident, and this can be removed with the appropriate amount of CaCl2. The final purified product occupied 130ml
(1.26mol), figure 11. The corresponding yields are as follows:
Based on 200ml (3.4mol) EtOH, 74%
Based on total EtOH 380ml (6.4mol) 40%
Clearly continuation of the reaction will get the yield closer to (1).
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs9_11.JPG">
<BR>
<IMG src="http://www.sciencemadness.org/scipics/Len1/ether_17.JPG">
Fractionation of starting fluid
A 493ml pressurised can of starting fluid, with 25% ether, and dimethyl ether as propellant was used. Both the can and a 1L receiver flask were
cooled to 0C before the contents of the can were emptied via a tube, while maintaining both containers in a freezing bath. This produced only 390ml of
fluid, and it was presumed that most of the ether was lost at this stage due to its co-vapourisation with the dimethyl ether. To overcome this, the
arrangement shown in figure 12 was employed. In this way 430ml were gathered - it is assumed the 493ml contents quoted on the can includes the
dimethyl ether propelant.
Some boiling chips were dropped into the flask, and fractionation on an insulated hempel collumn with a hot water bath was performed, figure 13. The
boiling commenced right away - but it wasnt allowed to be too rapid - a feat which can be accomplished by lowering and raising the water bath - and in
about 10 mins the first drops of fluid appeared in the condenser. The fraction boiling in the range 33-39C was gathered, which took about 90mins.
The volume of this fraction was 83ml, or 19% of the total liquid volume. This gives a 76% yield in the separation on the 25% total ether content
quoted. Figure 14 shows a thick film spectrum for both this fraction, and that of the previous synthsis, showing that a considerable amount of water
is still present in the present product, due to lack of a purification step. This can be removed with CaCl2 as before, but for many extraction
processes it is acceptable.
<IMG src="http://www.sciencemadness.org/scipics/Len1/Et_figs12_14.JPG">
<BR>
<IMG src="http://www.sciencemadness.org/scipics/Len1/ether_16.JPG">
Conclusion
Acid-catalysed ethanol dehydration is an efficient and cheap method for ether production, giving a maximum yield of about 74% based on ethanol. With
the present simple arrangement it is however enherently unstable and time consuming. Fractionation of strater fluid is a much faster simpler method,
it is however more expensive.
[Edited on 8-1-2008 by len1]
|
|
|
DeAdFX
Hazard to Others
Posts: 339
Registered: 1-7-2005
Location: Brothel
Member Is Offline
Mood: @%&$ing hardcore baby
|
|
hmm.. Nicely done on this topic and the chlorine topic. Keep up the good work!
|
|
|
organometallic
Hazard to Self
Posts: 53
Registered: 22-7-2007
Location: United Kingdom
Member Is Offline
Mood: No Mood
|
|
Yeah, really damn good work. I really enjoy your posts
In vials of ivory and coloured glass
Unstoppered, lurked her strange synthetic perfumes,
Unguent, powdered, or liquid - troubled, confused
And drowned the sense in odours.
|
|
|
smuv
National Hazard
Posts: 842
Registered: 2-5-2007
Member Is Offline
Mood: Jingoistic
|
|
Regarding the distillation of starting fluid:
I find it is best to use starting fluid which only uses CO2 as a propellant, I have encountered those which used isobutane and propane and noticed the
ether distilled contained these dissolved gases. This could be seen by the fact that when this cold distillate was poured onto a paper towel, it
fizzed on contact (like soda in a way).
Also if the starting fluid container does not have a spray nozzel tube attachment as yours does (I have never seen starting fluid sold with one) you
can easily pull off the spray nozzel from the can, and attach soft plastic tubing to the the valve; and transfer in this way. I have heard of people
(although I have never tried it) turning the can upside down and puncturing the bottom, releasing the compressed CO2 (in the head space above the
ether) and then simply pouring the mixture out of the can.
I like your idea about chilling the can before sparying, I will try this in the future (although even spraying alone seems to cool the can quite a
lot). I also can confirm similar yields, from the distillation of 6 cans of a 35% ether starting fluid I get about 650mL of ether (I collect from
room temp to 35c as the forerun seems to be ether).
EDIT: When distilling ether I have noticed that connecting a tube to the vac adapter outlet and routing it out a window, makes the entire process of
distilling ether nearly odor free.
[Edited on 24-3-2008 by smuv]
|
|
|
Sophism
Harmless
Posts: 6
Registered: 23-12-2007
Member Is Offline
Mood: No Mood
|
|
nice work
|
|
|
Saerynide
National Hazard
Posts: 954
Registered: 17-11-2003
Location: The Void
Member Is Offline
Mood: Ionic
|
|
Great read once again!!! And you own an FTIR?? 
"Microsoft reserves the right at all times to monitor communications on the Service and disclose any information Microsoft deems necessary to...
satisfy any applicable law, regulation or legal process"
|
|
|
len1
National Hazard
Posts: 595
Registered: 1-3-2007
Member Is Offline
Mood: NZ 1 (goal) - Italy 1 (dive)
|
|
I think yield would be higher in the procedure I outlined compared to what you did because here ether distilation is accompanied by the flux of an
uncondensable gas - this will carry some ether out of the apparatus with it, also makes distillation rate harder to control.
I do not think its so safe due to the higher rate of ether loss to the environment - but if there are no hot surfaces in the vicinity (ie youre using
a mantle) and no flames I think you should be alright.
The FTIR is mine - but as Ive said elsewhere on this forum, theres no reason why amatuers shouldnt have one these days, they can be bought for several
hundred dollars on eBay. Ive outlined the refurbishment I did on my FTIR elsewhere on the forum. Doing chemistry with compared to what it was like
before feels like suddenly being able to see.
Same applies to MS and NMR, but the FTIR is the most useful of these for following reactions.
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Nice work again, Len.
When the industrial process was based on this method, they ran it continuously for weeks. Ethanol was added continuously, some water was distilled
out as well, keeping the acid strength up, and separated from the ether through fractionation. This indicates that the acid should be reusable to
some degree.
Other catalysts that have been used include H3PO4, which would be a mix of condensed phosphoric acids at the reaction temperature, and aromatic
sulfonic acids. These cause less side reaction and charing, not oxidising the alcohol and thus releasing SO2; or at least that was claimed.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
| Quote: |
Is this safe? I was a little paranoid, I'm using an electric single element stove on a dimmer switch
|
Len, he didn't say a "mantle." Using a bare element in the presence of ether would make me nervous. I would preferably use a steam bath for ether,
but have also used a mantle (fiberglass covered element).
|
|
|
Panache
International Hazard
Posts: 1290
Registered: 18-10-2007
Member Is Offline
Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
|
|
The 'start-you bastard' product used in your illustration Len utilises dimethyl ether as the propellant. If the cans are dropped to below -50C, they
can be drilled through and decanted into a round bottom. A dry ice condenser will condense the dimethyl ether fraction that comes over at around -25C.
This ether is easily re-stored in a small bbq gas cylinder. It is a very useful thing, forming up to 35%solutions with water.
From there the di-ethyl ether can be distilled and so on.
Just additional information nothing else.
In case any are in dispute of this fact, because on the can it actually states the propellant as being CO2, however if you download the MSDS on the
product it states the propellant to be dimethyl ether. I have actually performed the reclaimation above and can tell you that dimethyl ether
condensed, making the claim on the can incorrect and the claim in the msds correct. Another fine example of australian attention to detail, lol.
[Edited on 26-8-2008 by Panache]
|
|
|
Engager
Hazard to Others
Posts: 295
Registered: 8-1-2006
Location: Moscow, Russia
Member Is Offline
Mood: Lagrangian
|
|
Thanks for this publication, it's very detailed and comprehensive. Good work! I've made two ~200ml batches of ether using your procedure, and yields
are exactly as you described. However i have 2 small comments. First is that ether prepared from C2H5OH/H2SO4 and purified as you described contains
some small ammount of water, boiling points are evident - final product start to destill at ~34C that corresponds to distillation of azeotropic
mixture of ether with water containing 98.74% of ether (boiling point 34.15C). Second is that ether tends to accumulate peroxides durring distillation
and they surely present in final product, to get rid of them it is very recomended to store final product above a small batch of KOH, it is insoluble
in ether, transforms forming hydroperoxides to insolube products and also acts as good dehydrating agent.
[Edited on 5-7-2009 by Engager]
|
|
|
jmneissa
Harmless
Posts: 29
Registered: 4-5-2009
Member Is Offline
Mood: No Mood
|
|
Hey great work however I have a question. You used methylated spirits which contain (most of the time) a mixture of ethanol, methanol, and many other
alcohols with ethanol comprising about 90% of the mixture. Do these 10% of impurities cause a problem in the synthesis? For example the boiling point
of ethanol is 78C while the boiling point of methanol is lower at 65C and isopropyl alcohol being higher at 82C when you distill of the primary
reaction leaving behind the black liquid wouldn't the alcohol distill over with the ethanol? If so do they react with the sulfuric acid forming a
separate product? I really would like to replicate your work and I have a can of Denatured Alcohol but I am wondering how these other alcohols present
with effect my product.
|
|
|
starman
Hazard to Others
Posts: 318
Registered: 5-7-2008
Location: Western Australia
Member Is Offline
Mood: No Mood
|
|
len works in Australia where the denaturant is usually MIBK.If you use a mixture of alcohols,you will get a mixture of ethers.If you have significant
methanol you will form significant dimethyl ether,which due to its very low boiling point will probably carry off a good deal of your target.(see
Panache a couple of posts above)
Chemistry- The journey from the end of physics to the beginning of life.(starman)
|
|
|
white rabbit
Harmless
Posts: 33
Registered: 29-11-2009
Member Is Offline
Mood: Groovy
|
|
I liked this "Practical guide" so much that I have duplicated,( as best I could), the entire procedure with the exception of the FTIR results. I used
Everclear ~191 proof for my source of EtOH rather than the SDA 200 because of its denaturing. Also I did run 750mL EtOH through the reaction bath
confirming that it can convert quite a bit before needing to be replaced. Here I have include some pics.
 This is the first setup.
 This is the raw ether 655mL
 Washing the product.
 Re distilling from the CaCL2
 Here it is, 320mL Diethyl Ether!
I really enjoyed the experiment. Thanks to Len1 for the "Illustrated Practical guide" !
White Rabbit
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Nice work, Rabbit - thanks for the pictures. You have a lot of nice equipment. It is of sufficient scale for production of reagents. I'm in the
process of acquiring some larger (24/40) scale equipment for that purpose.
Where did you get your equipment? EBay? Do you like the Graham condenser better than a West (Liebig style) condenser?
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
len1
National Hazard
Posts: 595
Registered: 1-3-2007
Member Is Offline
Mood: NZ 1 (goal) - Italy 1 (dive)
|
|
Very nice, I enjoyed your post. Thank you
|
|
|
Engager
Hazard to Others
Posts: 295
Registered: 8-1-2006
Location: Moscow, Russia
Member Is Offline
Mood: Lagrangian
|
|
Let's make ether picture gallery! My equipment is not so perfect as western, but is much cheaper and works just fine =)
My ether setup:
Reflux flask setup:
Condensing ether vapors:
Crude ether:
Pure ether redestiller setup:
Final product - pure ether:
[Edited on 23-12-2009 by Engager]
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
Very good! But because of its low boiling point, only 30ºC I believe (it gets that warm in my country in summer), and liability to form an explosive
peroxide on exposure to air and light, you will have to keep it in a refrigerator, and preferably sealed under argon (or a gas that you are sure it
will not react with or adversely affect any reactions in which it is used as a solvent or reagent).
[Edited on 25-12-09 by JohnWW]
|
|
|
len1
National Hazard
Posts: 595
Registered: 1-3-2007
Member Is Offline
Mood: NZ 1 (goal) - Italy 1 (dive)
|
|
ne hueva!
|
|
|
white rabbit
Harmless
Posts: 33
Registered: 29-11-2009
Member Is Offline
Mood: Groovy
|
|
Quote: Originally posted by Magpie  | Nice work, Rabbit - thanks for the pictures. You have a lot of nice equipment. It is of sufficient scale for production of reagents. I'm in the
process of acquiring some larger (24/40) scale equipment for that purpose.
Where did you get your equipment? EBay? Do you like the Graham condenser better than a West (Liebig style) condenser? |
Thanks Magpie. Yeah, I do have quite a bit of glassware. Sometimes, I buy a new piece on ebay and when I go to put it away, I find that I already have
one. Ooops! I bought some of my glassware on ebay, some I buy direct from Wilmad Labglass, and the rest I get from a glass shop I use for my custom
pieces.
The condenser in the pic is not a Graham, it is a jacketed "cool coil". I feel that the Graham has too much flow resistance for a first stage. The
cool coil works well and the jacket around it really makes the difference. It is basically a Liebig with a coil inside of it. The Graham may be better
for the second stage but I like the effectiveness,(greater surface area), of the Friedrich. I bought the jacketed cool coil from Wilmad Labglass.
I really like to seeing the hands on work all of you guys have posted.
White rabbit
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
JohnWW: bp of ether is a little higher, at ~35C. Storing it in the refrigerator is overkill unless you live somewhere rediculously hot. Peroxides
arent that much of a problem if you keep the bottle topped up and store in an amber bottle, preferably stabilised with some BHT. There are many posts
on ether peroxides and preventing their formation; copper supposedly does the job nicely, but requires a large surface area (a copper scourer stuffed
into the bottle should be sufficiently adeqate. Alternatively you could form a copper mirror on the inside of the bottle, using chemical deposition.
This can be done by electrolysis if you store your ether in aluminium bottles).
Argon is definately OTT, especially if you have limited headspace and an inhibitor.
[Edited on 25-12-2009 by DJF90]
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
Wow! I am jealous of all this equipment!
But I wondered: does 'wet' ether form a peroxide also? Well, I suppose it is 'yes,' but I meant that perhaps it is destroyed by water, and so safer to
store?... But anyway, copper sounds a very nice idea if it works well... I hadn't heard of that before. I would like to try this one day, so thank you
for the details since it will, I hope, be very useful!
|
|
|
aonomus
Hazard to Others
Posts: 361
Registered: 18-10-2009
Location: Toronto, Canada
Member Is Offline
Mood: Refluxing
|
|
I've seen ampules of hygroscopic liquids from sigma stored over copper shot/powder. I'm not sure how well simply taking a lump of copper or shavings
would work, probably too dirty?
Also, doesn't storing over KOH precipitate any intermediate before the peroxide forms?
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Seems to me a transition metal would catalyze the reaction. Or is that more of an iron thing?
The usual solution is easy enough: the last bottle of ether I used claimed ethanol as a stabilizer. Add back a few drops of the swill you started
with and all's well.
Tim
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
I'm not sure why hygroscopic liquids were stored over copper aonomus; the function of the copper with ether is to inhibit the formation of the
peroxide.
Tim: I think the role of the copper is to actually catalyse the decomposition of any peroxide that may form. Definately a good thing. I had a paper on
it somewhere but cannot find it. I'm familiar with ethanol being used to stabilise chloroform but its use in ether is new to me. Thanks for sharing!
|
|
|
| Pages:
1
2
3 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
