Author Topic: nitroethane synthesis  (Read 1761 times)

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lastchance

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nitroethane synthesis
« on: September 22, 2004, 12:15:00 PM »
From Kornblum and Ungande, Organic Syntheses, v.38, p.75, 1958 we take the synthesis of silver nitrite as our initial step.

Under yellow photograhic light prepare a solution of 76 g (1.1 mol) of sodium nitrite in 250 ml water in a 1 L flask. Prepare a solution of 169.9 g of silver nitrate (1 mol) in 500 mL water. Slowly add the silver salt solutionto the sodium nitrite solution with vigorous stirring. After addition is complete, cease stirring and allow the mixture to stand in the dark for 1 hour. A yellow precipitate will form. This is filtered with suction, collected, suspended in 250 ml fresh water, and filtered again. Repeat this washing again, collecting the solid after filtering. Dry the product to constant weight in a vacuum dessicator over KOH pellets. [Note: This means to place the pellets in the bottom of the dessicator, preferably in a glass dish. The ceramic stand on which the sample is supported is put in place and the product, spread thinly on a glass plate, is placed on the support. It does *not* mean to pour the product over KOH pellets. Vacuum is maintained on the desiccator during the drying period. Drying to constant weight means that you weigh the product, dry longer, weigh again, dry longer, weigh again, and so on until two consecutive weights agree closely; i.e., in the last decimal place to which your balance will weigh.] The drying may be hastened by washing the product once with methanol after the two water washings. Should yield about 134 g (87%). Store in a brown glass bottle and place in a dark storage area until ready to use.

Kornblum, et al, in J. Amer. Chem. Soc. 78, 1497, 1956 showed that alkali nitrites, especially sodium nitrite, can be used in the preparation of nitro compounds if DMF was used as the solvent. Thus, if DMF is available, the silver nitrite synthesis may be omitted. Use 1-iodoethane dissolved in DMF and add excess sodium nitrite in DMF with vigorous stirring at 0 C. Stir for 2.5 hours until reaction is complete. If 1-bromoethane is used, stir for 6 hours. Yields 60%.

Using the silver nitrite method, cool 100 g of silver nitrite (0.65 mol) in 150 ml of dry ether to 0 C in a 3 neck 500 ml flask(again in a darkened room or using yellow light). Drop in 1-iodoethane (or 1-bromoethane) over a 2 hour period while stirring constantly and maintaining 0 C and dark conditions. Note that 0.65 mol of the silver salt is used so 0.50 mol of the halo-ethane should be used. Stir for 24 hours at 0 C, then 36+/-12 hours at room temperature. [Note: If the bromo is used, stirring for 48+/-12 hours at room temperature is necessary] Use the Beilstein test for halogens. The reaction is complete when no halogen is detected. [Drop a few drops of the reactant solution into a test tube containing an alcoholic solution of silver nitrate and note if a precipitate occurs. If so, the reaction is not complete. The Beilstein test uses a small coil of copper wire in a test tube. A small portion of the reactant solution is added and it is noted if reaction occurs. Silver will replace the copper. The first test is quicker and easier to perform] Silver iodide (or bromide) will precipitate over this time. Filter off the silver salt, washing with several portions of ether. Evaporate (and recover if possible) the ether at room temperature. [This may be replaced with distillation of the ether, using a water bath, at atmospheric pressure. A 2x45 cm column packed with 4 mm pyrex helices is used. The residue is distilled at 5 mm. A more efficient column is not used due to the instability of the nitrite of ethane. Maintain anhydrous conditions since the nitrite ester will hydrolze to the alcohol and will be difficult to separate.] Then distill the product at 5 mm. The nitrite of ethane will be the initial fraction, followed by an intermediate fraction, then the nitroethane will boil over. Produces about 83%.


I was wondering if substituting DMSO for DMF 1 molar would make a diffference

Rhodium

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UTFSE
« Reply #1 on: September 22, 2004, 05:22:00 PM »

lastchance

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You really try to make my life hard
« Reply #2 on: September 23, 2004, 12:25:00 AM »
I amcurious about the exchnge of KOH pellets with drying weight.  ANy ideas?

Rhodium

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Huh?
« Reply #3 on: September 23, 2004, 03:48:00 AM »
I don't understand what you mean with "the exchnge of KOH pellets with drying weight".


lastchance

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Do you
« Reply #4 on: September 23, 2004, 11:44:00 AM »
keep addding KOH pellets to bottom of plate while drying to equal weight of liquid evaporating? I understnad not to pour into product or you will ruin it.

 [Note: This means to place the pellets in the bottom of the dessicator, preferably in a glass dish. The ceramic stand on which the sample is supported is put in place and the product, spread thinly on a glass plate, is placed on the support. It does *not* mean to pour the product over KOH pellets. Vacuum is maintained on the desiccator during the drying period. Drying to constant weight means that you weigh the product, dry longer, weigh again, dry longer, weigh again, and so on until two consecutive weights agree closely; i.e., in the last decimal place to which your balance will weigh.]

hest

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NaOH
« Reply #5 on: September 23, 2004, 02:25:00 PM »
Ohh That wat it means

Drying can bee done in manye wayes. Vacuum will doo alone, and you can substituté KOH with NaOH/CaCl ect.

MargaretThatcher

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15 psi
« Reply #6 on: September 25, 2004, 03:05:00 PM »
"Any sugesstions as to why this would not work?"

15 psi over say 120 square inches = 1800 pounds, almost a ton.

Make sure it is thick glass. You'll also need some silicon grease.


lastchance

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Hey what can I say?
« Reply #7 on: September 25, 2004, 06:34:00 PM »

lastchance

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You made me laugh for 15 minutes
« Reply #8 on: September 25, 2004, 06:37:00 PM »

indole_amine

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why would you want to dry solids?
« Reply #9 on: September 25, 2004, 07:02:00 PM »
As you already wrote: "Kornblum, et al, in J. Amer. Chem. Soc. 78, 1497, 1956 showed that alkali nitrites, especially sodium nitrite, can be used in the preparation of nitro compounds if DMF was used as the solvent. Thus, if DMF is available, the silver nitrite synthesis may be omitted. Use 1-iodoethane dissolved in DMF and add excess sodium nitrite in DMF with vigorous stirring at 0 C. Stir for 2.5 hours until reaction is complete. If 1-bromoethane is used, stir for 6 hours. Yields 60%."

So you obviously don't have to prepare any silver nitrite when you use DMF.

And quote from the nitroalkane synthesis document on Rhodium's site:

"dimethyl sulfoxide (DMSO) can be substituted for the dimethylformamide (DMF) as solvent. Ethylene glycol also works as solvent."

So it should be clear to the attentive reader that both DMF and DMSO as well as ethylene glycol allow for the use of sodium nitrite directly, without having to prepare and dry a solid silver salt beforehand!


Still I am not able to see how this is related to building a low-budget vacuum desiccator - as drying solids isn't needed in this synthesis, neither with DMF nor with DMSO. And if you'd researched the document properly, you would've dicovered

this link

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/ethyl.bromide.html) - quote:

"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°C collected in a separate flask. This consists of ethyl bromide which may contain a little ether."

This is the only drying process being necessary - and I really can't see any other drying step required for this preparation..

(except you insist on using the tedious AgNO2 preparation of course)


indole_amine

moo

  • Guest
EtBr/NaNO2/DMSO to EtNO2 problems
« Reply #10 on: September 26, 2004, 04:02:00 AM »
Alas, the NaNO2/DMSO/ethyl bromide route to nitroethane doesn't work too well. TFSE reveals that bees have had problems during the years.

Post 77924 (missing)

(Biscuit2: "Nitroethane - Polymerised disaster?? Help please!", Methods Discourse)
An explanation is offered in this thread, obviously nitrite scavengers help.

Post 173510

(Karl: "Re: Roads to Nitroethane", Chemistry Discourse)

Post 250792

(SpicyBrown: "Problem encountered during Nitroethane synth.", Methods Discourse)

Post 502445

(hest: "Nitroethane", Methods Discourse)

Post 502896

(karel: "Nitroethane synthesis", Methods Discourse)
The convenience of using AgNO2 despite it's price and light sensitivity is discussed in this thread.


lastchance

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Piperonal
« Reply #11 on: September 26, 2004, 07:11:00 PM »
I heard Ethylene glycol sucked as a solvent and yields were so poor that it was discarded.  I will find the article later to prove my point.  Mabe these guys were in a hurry... They were making over 20 liters of the stuff.