Nitroethane

[moo]

The bees know that the nitroethane preparation procedure from sodium ethyl sulfate given in

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

doesn't give the results expected and doesn't run at 125-130 degrees like stated. This is not because of the original article, but because the very terse abstract posted in Chemical Abstracts on which the procedure is based on. The actual method from the article referenced is a bit different and it appears that the same goes for the whole series on Gerard Desseignes preparations of nitroalkanes:


Manufacture of nitromethane from dimethyl sulfate.
Desseigne, Gerard; Giral, Henri.
Memorial des Poudres, 34, 13-27 (1952).  Journal language unavailable.
CAN 49:7855  ISSN 0369-1535

Abstract
Optimum conditions for manuf. of MeNO2 were detd. for the reaction of 3 moles NaNO2 per mole Me2SO4 in 90 g. water per 100 g. NaNO2.  Addn. of 0.025 mol. K2CO3 per mol. NaNO2 improved the yield from 50 to 66%.  Castor oil or colza oil was added as an antifoaming agent.  The reaction proceeds in two steps, the first at 60 Deg, the second at 115 Deg to 120 Deg.  Distn. of the product, required to remove water and MeOH, is complicated by the azeotropes of 24% MeNO2 in water and 12.5% in MeOH.  The price of 273 francs/kg. MeNO2 for raw materials by this process is compared with 811 francs/kg. by the chloroacetic acid process.  13 references.

Manufacture of nitromethane from sodium methyl sulfate.
Desseigne, Girard; Giral, Henri.
Memorial des Poudres, 34, 29-47 (1952).  Journal language unavailable.
CAN 49:7856  ISSN 0369-1535

Abstract
cf. C.A. 47, 10229b, and preceding abstr.  Sodium methyl sulfate (I) is made by treating 1 mol. 20% oleum per 2 mols. MeOH at 50 Deg for 30 min., dilg. with water and neutralizing with Na2CO3; yield, 78%. MeNO2 is made by treating 1 mol. I per 1.5 mols. NaNO2 at 115 Deg to 120 Deg with 0.0625 mol. of K2CO3 present; yield, 69%. Distn. of the product from the reaction gives 87.3% pure MeNO2.  The MeNO2-MeOH azeotrope is treated with oleum to esterify MeOH, followed as before by neutralizing with Na2CO3.

Preparation of nitroethane.
Desseigne, Gerard; Giral, Henri.
Memorial des Poudres, 34, 49-53 (1952).  Journal language unavailable.
CAN 49:4388  ISSN 0369-1535

Abstract
cf. C.A. 47, 10229b.  Na Et sulfate (85% yield) is made by treating 1 mole 20% oleum with 2 moles ethanol at 45 Deg for 30 min. and neutralizing with Na2CO3.  EtNO2 (42.6%) is made by treating 1.5 moles NaNO2 with 1 mole Na Et sulfate at 125-30 Deg in the presence of 0.0625 moles K2CO3.

Full article

The last ref, the one most of us are more interested of, was kindly retrieved by Lugh. It also contains the preparation of sodium ethyl sulfate as mentioned in the abstract and another preparation of nitroethane starting from diethyl sulfate yielding 27% based on the two ethyl groups in diethyl sulfate or 54% based on diethyl sulfate. In the article the authors state that the notes pertaining to the similar nitromethane preparation are also valid for this one, so they were omitted from this article. I don't know if there's anything really important but if there are any problems with this one, we know where to start looking for the answers. Here is what I considered most important freely translated with annotations. We'd know it's correct if someone better at french could check it for errors.


Properties of nitroethane

Molecular mass 75 g/mol
Boiling point at 760 mmHg 114,8°C
Vapour pressure at 20°C 15,6 mmHg
Freezing point -90°C Although Merck sez it's about -50°C
Density: 1,0685 kg/l at 4°C; 1,0561 kg/l at 15°C; 1,052 kg/l at 20°C
Index of refraction at 20°C 1,3916
Solubility in water at 20°C 4,52 g per 100 g of solution
Solubility of water in nitroethane at 20°C 0,85 g per 100 g of solution
Azeotrope with ethanol 18,4% nitroethane, boiling point at 760 mmHg 77,94°C
Azeotrope with water 69,5% nitroethane, boiling point at 760 mmHg 87,32°C

Equipment

The equipment is the same as used in the preparation of nitromethane from sodium methyl sulfate.
I assume it is a distillation setup equipped with an addition funnel and two thermometers, one for vapour temperature as usual and another reaching to the reaction mixture.

Procedure

The reaction flask is charged with:
26,5 g (0,0625 x 3 moles) of technical K₂CO₃ dissolved in 137 g of water
320g of 97% technical sodium nitrite
6 ml of cetyl-oleic alcohol or oleic alcohol (antifoaming agent)
Volume of the mixture is about 420 milliliters.

The mixture is heated on a glycerol bath at 130°C with stirring. The addition funnel is charged with 750 ml of an aqueous solution of 444 g (3 moles) sodium ethyl sulfate. The solution is added to the reaction mixture during 50-60 minutes at a suitable rate to keep the reaction temperature at 125-130°C. It is necessary to maintain vigorous agitation of the reaction mixture to ensure good dispersion of the salts precipitating (sodium sulfate) and to break the foams which form in the reaction vessel during about 30 minutes. The distillation of nitroethane begins when the addition is started, the temperature of the vapours being close to 100°C. When the addition of the sodium ethyl sulfate solution is complete 100 milliliters of water are added during 10 minutes to distill all formed nitroethane from the reaction mixture. The formation of non-condensable gases accompanying the reaction begins at 80°C. Ethyl nitrite?

Distillation and purification of nitroethane

The distillate separates in two layers which are separated. The distillate can also be distilled at atmospheric pressure without separating the layers with a 12 plate distillation column (25 mm diameter, height 40 mm) from a one liter flask. Distillation starts at 30°C. The forerun weighing 2-3 g coming over below 74°C is discarded. The temperature then settles at 87°C and the distillation is stopped when the temperature reaches 99,8°C. The distillate separates in two layers: The lower phase (nitroethane saturated with ethanol and water) weighing 104 g, containing 91,6 g nitroethane (88,2%). The upper phase (ethanol and water saturated with nitroethane) weighing 96,1 g, containing 4,39 g nitroethane (4,56%). The rectification of the lower phase affords pure anhydrous nitroethane.

Yield of nitroethane: 96 g (1,28 moles), 42,6% based on sodium ethyl sulfate.



So it seems it also eliminates the need for preparing solid sodium ethyl sulfate, as it is possible to make ethylsulfuric acid with MeOH/H₂SO₄/Na₂SO₄ and neutralising it carefully after filtration to arrive at an aqueous solution of the the salt ready for addition. Colza or castor oils as an antifoaming agent might also be worth trying, it seems something is needed anyway.