Author Topic: Bromoethane synthesis  (Read 2987 times)

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lastchance

  • Guest
Bromoethane synthesis
« on: September 04, 2004, 12:37:00 PM »
Just in case anyone knows or cares Nitroethane can be easily made with Bromoethane and Sodium Nitrite.  Problem being is Bromoethane is primarily a soil fumigate and from what I hear the EPA has pretty much bannned it due to high toxity and other alternatives.  Are there any decent synthesis to make Bromoethane (Ethyl Bromide)?  I am refering to Rhodiums method 3 Nitroethane Synthesis: A Compilation

Lestat

  • Guest
Direct bromination of the alcohol would, in...
« Reply #1 on: September 04, 2004, 01:32:00 PM »
Direct bromination of the alcohol would, in this case, yield bromal hydrate (similar to chloral, but don't get any ideas, its a LOT more toxic)

What about gassing of bromine with ethane?

Edit: Would the same procedure using methyl bromide yield nitromethane?


Captain_America

  • Guest
EtX
« Reply #2 on: September 04, 2004, 03:06:00 PM »
For the swap consider making iodoethane. There is a writeup posted by russian bees using KI

Post 301629

(Antoncho: "Two tried-and-true ways to make MeI !", Chemistry Discourse)
it will work for EtI too.

Btw, why not make the nitroethane from ethanol, sulfuric and NaNO2 and avoid that extra step? UTFSE:

Post 233762 (missing)

(Antoncho: "Kitchen nitroalkane success!", Chemistry Discourse)


If you still prefer the swap, maybee try PTC...

Bee sure to report back!

gsus

  • Guest
ethyl bromide
« Reply #3 on: September 04, 2004, 04:21:00 PM »
the nitroalkane FAQ, right above the compilation.

farther down, Vogel, pp. 278-9. or any other book of that sort of the last 150 years.


karl

  • Guest
If you do a search you will find that myself...
« Reply #4 on: September 05, 2004, 06:10:00 AM »
If you do a search you will find that myself and some others have had problems with Bromoethane and NaNO2 with DMSO or DMF - It looked good on one of the references where they tested it extensively for nitromethane, but I think their data on nitroethane was a bit dubious.


hest

  • Guest
Nitroethane
« Reply #5 on: September 05, 2004, 07:07:00 AM »
so doo I.
I have truet the reaction 5-10 times, with realye crapye yeald's (in the 5-15% range).
Next time I use silvernitrite instead

cattleprodder

  • Guest
Bromoethane synthesis
« Reply #6 on: September 05, 2004, 05:46:00 PM »
What about ethyl alcohol plus phosphorous tribromide?

EtOH + PBr3 --> EtBr

moo

  • Guest
You could do that... but why use a reagent...
« Reply #7 on: September 06, 2004, 09:40:00 AM »
You could do that... but why use a reagent that has much better uses to do something you can pull off with sulfuric acid and a bromide salt?


Captain_America

  • Guest
Reference missing?
« Reply #8 on: September 08, 2004, 05:17:00 AM »

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitroalkane.html



Preparation of Ethyl Bromide

1500 ml of concentrated H2SO4 was added to 900 ml H2O, then cooled. Then 1.5 l of absolute ethanol was slowly dripped in, carefully to avoid temperature rise. Cool the mixture and add 1100-1200 g KBr (or equimolar amount of NaBr). Heat the mixture on a sand-bath at the lowest temperature at which the ethylbromide distills over, collect it in water. Wash the ethyl bromide again with water and dry it with CaCl2. Yield 90-96%.


What's the ref for this prep? Using KI instead of KBr would probably give as good results for EtI, since it is almost identical to the synth posted by Antoncho, don't you think so? Great method.

Rhodium

  • Guest
The preparation of ethyl bromide
« Reply #9 on: September 08, 2004, 07:55:00 AM »
The missing reference is one of the two following ones, but I don't know which one:

I. The preparation of ethyl bromide
Alfred Holt, J. Chem. Soc., Trans., 109, 1-2 (1916)
DOI:

10.1039/CT9160900001



CLXIV. The preparation of ethyl bromide
Frank Edwin Weston, J. Chem. Soc., Trans., 107, 1489-1490 (1915)
DOI:

10.1039/CT9150701489




I also happened to find this reference in connection to the two above, maybe it is of interest as well:

CCCLIX. The effect of intensive drying on the rate of distillation and on the vapour pressure of ethyl bromide
John William Smith, Journal of the Chemical Society 2573-2583 (1931)
DOI:

10.1039/JR9310002573




lugh

  • Guest
Another Old Ethyl Bromide Preparation
« Reply #10 on: September 09, 2004, 07:17:00 PM »
From Cohen's Practical Organic Chemistry

Ethyl Bromide (Monobromethane), C2H5Br.
De Vrij, Jahresber., 441 (1857)

100 grms potassium bromide.
100 grms (54 c.c.) conc. sulphuric acid.
 60 grms (75 c.c). absolute alcohol


Fit up the apparatus as shown. The distilling flask should have a capacity of not less than I litre, and is attached to a long condenser. An adapter is fixed to the end of the condenser, dipping into a conical flask (250 c.c.), which serves as receiver. The alcohol and sulphuric acid are mixed in the distilling flask and cooled to the ordinary temperature tinder the tap. The potassium bromide, coarsely powdered, is then added. The flask, which is closed with a cork, is fixed to the condenser and heated on the sand-bath. A sufficient quan­tity of water is poured into the receiver to close the end of the adapter. After a short time the liquid in the flask begins to boil and froth up, and the ethyl bromide, in the form of heavy drops of colourless liquid, distils and collects at the bottom of the receiver. If the liquid threatens to froth over, the flask must be raised from the sand-bath for a moment. The distillation is continued until no further drops of oil appear at the end of the condenser. As the ethyl bromide has a low boiling point (38-39c), it is desirable to surround the receiver with ice during this operation. The distillate is now removed and poured into a separating funnel, and the lower layer of ethyl bro­mide separated. The water is thrown away and the ethyl bromide poured back together with about an equal bulk of dilute sodium carbonate solution and shaken up. The ethyl bromide is withdrawn, as before, and again shaken up with water. Finally, it is carefully separated from the water and run into a dry distilling flask. The small quantity of water which remains. and renders the liquid turbid, is removed by adding a dehydrat­ing agent.
Dehydration. Moisture can be readily removed from liquids by adding a solid hygroscopic substance which does not act chemically upon the liquid. The common dehydrating agents are calcium chloride, potassium carbonate, sodium sulphate (anhydrous), quicklime, etc. Alkalis can not of course be used for dehydrating organic acids, nor can calcium chloride be employed in conjunction with alcohols or organic bases, with which it combines. In the present instance it can be used. A few small pieces of the granulated or fused calcium chloride are added to the liquid. The flask is corked and left to stand for some hours until the liquid becomes clear. It is then distilled. A thermometer is inserted into the neck of the flask with the bulb just below the side tube. The flask is attached to a condenser and heated gently on the water bath, so that the liquid distils at a moderate speed (2-3 drops a second). The temperature is noted and the portion boiling at 35-43° collected in a separate flask. This consists of ethyl bromide which may contain a little ether. Yield 75-80 grams.



Kinetic

  • Guest
Preparation of ethyl bromide
« Reply #11 on: September 11, 2004, 08:05:00 AM »
Here are the two articles requested by Captain_America:

CLXIV. The preparation of ethyl bromide
Frank Edwin Weston
Journal of the Chemical Society, Transactions
, 107, 1489-1490 (1915)




I. The preparation of ethyl bromide
Alfred Holt
Journal of the Chemical Society, Transactions
, 109, 1-2 (1916)


Captain_America

  • Guest
tnx K
« Reply #12 on: November 02, 2004, 05:15:00 PM »