Introduction.
I present to you the three simplest syntheses of nitroethane:
- From sodium ethyl sulfate and a metal nitrite.
- From ethyl halide and silver nitrite.
- From ethyl bromide (iodide) and sodium nitrite.
This list allows selecting a suitable reagent that can be purchased in your area. According to local prices for reagents, prices for final product and reagent availability, you can select more reasonable synthesis way.
Appearance: oily liquid, fruity odor
Boiling Point: 112.0 to 116.0 °C/760 mmHgMelting Point: -90 °C
Molecular Weight: 75.067 g/mol
Density: 1.054 g/ml (20° C)
Refractive Index: 1.3917 at 20 °C/D; 1.39007 at 24.3 °C/D
From sodium ethyl sulfate and a metal nitrite.
1.5 mole sodium nitrite (103.5 g) is intimately mixed with 1 mole of sodium ethyl sulfate (158 g) and 0.0625 moles of K2CO3 (8.6 g). The mixture is then heated to 125-130 °C, at which temperature the nitroethane distills over as soon as it is formed. The heating is discontinued when the distillation flow slackens considerably, and the crude nitroethane is washed with an equal amount of water, dried over CaCl2, and if needed, decolorized with a little activated carbon. The nitroethane is then re-distilled, collecting the fraction between 114-116 °C. Yield 42-46% of theory.
A more detailed description of the synthesis can be found here. There is nitromethane synthesis method, which can be converted to nitroethane synthesis with. You need to substitute dimethyl sulphate to diethyl sulphate and recount reagents masses .
From ethyl halide and silver nitrite .
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 (in a darkened room or using yellow light). Add 0.5 moles of ethyl halide (78 g ethyl iodide or 55 g of ethyl bromide) dropwise over a 2-hour period while stirring constantly and maintaining the temperature at 0 °C and dark conditions. Stir for 24 hours at 0 °C, then 24 hours at room temp if using ethyl bromide, and 48 h if using ethyl bromide .
(Test for halogens to see when the reaction is completed, through adding a few drops of the reaction mixture to a test tube containing an alcoholic solution of silver nitrate and note if a precipitate appears. If so, the reaction is incomplete. The Beilstein test can also be used, it uses a small coil of copper wire in a test tube to which a small portion of the reaction mixture is added, and it is noted if reaction occurs, where elemental silver will deposit on the surface of the copper coil.) Silver iodide (or bromide) will precipitate in the solution during the course of the reaction. Filter off the silver salt, and wash it with several portions of ether. Evaporate the ether at room temperature. (This may be substituted with distillation of the ether using a water bath at atmospheric pressure. A 2x45 cm column packed with 4 mm pyrex helices is used. A more efficient column is not used due to the instability of the ethyl nitrite formed as a by-product in the reaction. Maintain anhydrous conditions, since the ethyl nitrite will hydrolyze to ethanol and will be difficult to separate.) Then vacuum distill the residue at about 5 mm Hg. The ethyl nitrite will be the initial fraction, followed by an intermediate fraction, then the nitroethane will distill. Atmospheric distillation may reduce the yield. The yield is about 83% of theory.
From ethyl bromide (iodide) and sodium nitrite (DMF).
32.5 grams of ethyl bromide (0.3 moles) was poured into a stirred solution of 600 ml dimethylformamide (DMF) and 36 grams dry NaNO2 (0.52 mole) in a beaker standing in a water bath keeping the solution at room temperature as the reaction is slightly exothermic. Always keep the solution out of direct sunlight. The stirring was continued for six hours. After that, the reaction mixture was poured into a 2500 ml beaker or flask, containing 1500 ml ice-water and 100 ml of petroleum ether. The petroleum ether layer was poured off and saved, and the aqueous phase was extracted four more times with 100 ml of petroleum ether each, where after the organic extracts were pooled, and in turn was washed with 4x75 ml of water. The remaining organic phase was dried over magnesium sulfate, filtered, and the petroleum ether was removed by distillation under reduced pressure on a water bath, which temperature was allowed to slowly rise to about 65 °C. The residue, consisting of crude nitroethane was distilled under ordinary pressure (preferably with a small distillation column) to give 60% of product, boiling at 114-116 °C.
The ethyl bromide reacts with NaNO2, forming nitroethane and ethyl nitrite.
This method can be varied in a few ways. Firstly, dimethyl sulfoxide (DMSO) can be substituted for the dimethylformamide (DMF) as solvent. Ethylene glycol also works as solvent, but the reaction proceeds pretty sluggishly in this medium, allowing for side reactions, such as this: RH-NO2 + R-ONO => R-(NO)NO2 + R-OH. KNO2 can also be used instead of NaNO2. If NaNO2 is used in DMF, 30 g (0.5 mol) of urea can also be added as nitrite scavenger to minimize side reactions, as well as simultaneously increasing the solubility of the NaNO2 and thereby significantly speeding up the reaction.
If the ethyl bromide is substituted with ethyl iodide, the required reaction time is decreased to only 2.5 h instead of 6 h. In case ethyl iodide is employed, a slight change in the above procedure needs to be done. The pooled pet ether extracts should be washed with 2x75 ml 10% sodium thiosulfate, followed by 2x75 ml water, instead of 4x75 ml water as above. This to remove small amounts of free iodine.
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