Easy nitroethane in quantitative yield

[Rhodium]

Patent US4319059

This patent shows an easy route from ?-bromopropionic acid to nitroethane in excellent yield. The patent also say that Magnesium chloride, bromide or sulfate may be used instead of the magnesium methoxide, but it doesn't say if this affects yields.

The reaction proceeds as follows: In the polar aprotic solvent DMSO, the alpha-bromopropionic acid reacts in an S_N2 fashion with nitrite ion to give ?-nitropropionic acid and bromide ion. The role of the Mg²⁺ ion in the reaction is to facilitate the decarboxylation (removal of CO₂) from the intermediate nitro acid, as it forms a chelate between one of the oxygen atoms on the nitro group and the oxygen anion of the carboxylic acid. The electron-withdrawing nature of the nitro group makes the carboxylic acid group labile, and it can easily be given off as carbon dioxide. If magnesium methoxide is used in place of the other magnesium salts, the carboxylic acid is directly deprotonated, probably making the reaction go even faster.

There is no workup mentioned in the patent, but I'd suggest flooding with water (or using large amounts of dilute (5%) HCl in the hydrolysis step), and then extract the nitroethane with dichloromethane, ether or possibly petroleum ether. Then the combined organic layers are washed first with water and then with a concentrated NaCl solution, followed by drying the organic phase over anhydrous MgSO₄, which is then filtered off. Then the solvent is removed distilled, and the residual crude nitroethane is fractionally distilled at 114-115°C.

?-Bromopropionic acid can be made from propionic acid and phosphorous tribromide (from red phosphorous and bromine, the

Hell-Volhard-Zelinsky Reaction

(http://themerckindex.cambridgesoft.com/TheMerckIndex/NameReactions/ONR180.htm) reaction, or by HBr bromination of lactic acid (?-hydroxypropionic acid).


_{T h e   H e l l - V o l h a r d - Z e l i n s k y   R e a c t i o n}


Example 1

To a mixture of magnesium methoxide (0.11 mole) and dimethyl sulfoxide (50 ml) ?-bromopropionic acid (0.11 mole) was added at 20°C. with stirring. To this mixture a solution of sodium nitrite (0.145 mole) in dimethyl sulfoxide (65 ml) was added at room temperature. Then, the reaction mixture was stirred at room temperature for 6 hours and was neutralized upon addition of diluted hydrochloric acid. Analysis of the reaction mixture indicated more than 99% conversion of ?-bromopropionic acid and 94.5% yield of nitroethane.

Example 2

In the manner of Example 1, sodium nitrite, alpha-bromopropionic acid and magnesium methoxide were reacted in dimethyl sulfoxide as the aprotic solvent. The reaction time was 2 hours for one run and 22 hours for another. Reaction was conducted at room temperature. The run at 2 hours converted only 94.5% of the acid and yielded 72.7% nitroethane. The second run at 22 hours gave a conversion of >99% and a yield of 100%.

At room temperature the reaction apparently takes about 4-5 hours to go to completion. At higher temperatures of 40°C up to about 75°C the reaction time is shorter. Thus, one or two hours or even less time at 75°C will completely convert the bromoacid to the intermediate which can then be decomposed to the nitroalkane.

When using dimethyl sulfoxide as solvent temperatures approaching 100°C should be avoided since the solvent will volatilize and decompose at about 100°C. Other aprotic solvents may not have this disadvantage.

[Osmium]

Nice.

Some ideas regarding the workup:
Flooding with water and extracting is tedious and wasteful, and requires other solvents. Since EtNO2 forms azeotropes with all kinds of different solvents selecting the wrong one will cause a lot of headaches.

I came up with the following variations, which should work theoretically:

1) When the reaction is finished neutralise with another (organic?) acid which doesn´t contain any or only a little water. Then add a solvent known to form an azeotrope with EtNO2 and distill out that azeotrope. I think the lower alcohols should work ok for this step. Then you can either separate the EtNO2 by flooding with water, extracting the EtNO2 and recycling the alcohol by distillation. Any EtNO2 not extracted will distill over with the alcohol, and by reusing it you will limit EtNO2 losses during the next workup. Well, that isn´t really an improvement over the workup suggested above, so why not simply use the alcohol/EtNO2 mixture for your desired reaction. When the azeotrope composition is high enough in EtNO2 it can be directly used in nitropropene syntheses, which often use an alcohol co-solvent anyway.

2) I think this is the best way to go:
After neutralising apply vacuum and distill the EtNO2 directly out of the reaction mixture. The vacuum requirements aren´t high, all you want to do is depress the EtNO2 boiling point enough so it will be around 60-80°C. or you pull a little more vacuum and simply rotovap the EtNO2 off  
 
By using another dipolar-aprotic solvent like DMF one be able to distill the EtNO2 without vacuum.

If that reaction could be made catalytic in Mg(OMe)2, it might even be possible to distill the EtNO2 out as soon as it is formed, either under vacuum or with no vacuum at all, which should speed up the reaction even more due to the elevated temperature.

[Rhodium]

Nitroethane does not form an azeotrope with DCM, as was pointed out by someone earlier, so I still think that would be a good idea. The nitroethane will definitely travel over to the DCM layer rather than staying in a DMSO/H2O mixture. The water/brine washes of the organic layer is to remove carried over DMSO (but that may not be necessary, just distill after drying the organic layer).

[halfapint]

Lactates are real cheap in the food industry. In case it's inconvenient to get down to the lactic acid store, calcium lactate can bee proudly home brewed by local bacilli. Just train them in this procedure:

Lucas, Organic Chemistry, 1935, p. 497:
Lactic Acid fermentation of sugar.
The fermentation process takes place when decaying cheese, which contains the bacillus (Bacillus delbruchii), milk, and calcium carbonate, are added to a solution of sugar in water. The milk is necessary for the growth of the bacillus, and the carbonate, by neutralizing the lactic acid, prevents the building up of free acid which is detrimental to the fermentation process. The optimum temperature is 35-45. If the operation is continued too long, the calcium lactate will dissolve, due to the effects of a second fermentation, the butyric acid fermentation. The calcium lactate can be purified by crystallization. Crude lactic acid is obtained by the action of sulfuric acid upon the calcium salt... Rapid distillation at low pressures (around 1 mm.) gives a fairly pure [dl-]lactic acid.

Works for my buddy SWIM. Well, she drinks olive juice. 2-bromo-propionic acid has a density of 1.7000, mp 25.7, and bp 203.5^o.

turning science fact into <<science fiction>>

[Antibody2]

or by HBr bromination of lactic acid (alpha-hydroxypropionic acid).

i wouldn't suppose that is as simple as mixing equimolar quantites of each, would it? little reflux mayhap? and would 48% do it? or would some H2O2 be reqd as well?

"All those memories lost like rain..."

[Osmium]

I don´t have a detailed writeup for this reaction right now (shouldn´t be too difficult to find one though), but it looks like a simple SN2 reaction, meaning the usual R-OH ---> R-X procedures might work. Will investigate.

[foxy2]

A Simple and Efficient Method of Preparing alpha-Bromo Carboxylic Acids.
Tetrahedron Lett.  (1998),  39(52),  9621-9622.

Abstract
A new and convenient method for a-bromination of aliph. carboxylic acids is reported.  Heating carboxylic acids for 16 h at 85 °C in trifluoroacetic acid with 1.5 equiv of N-bromosuccinimide and a catalytic amt. of concd. H2SO4 leads to good yields of the resp. a-bromo carboxylic acids.

Procedure
Optimal ratio of H2SO4/TFA was found to be 2.5mL/50mL.  Dibromos were not formed in significant quantities even with a 50% excess of NBS.  At 0.1 mol scale in 50mL TFA, 2.5mL H2SO4, and 1.5 equivalents NBS, conditions 85C for 16hours, the yeilds are as follows.

Acetic      88%
Propionic   89%
Butyric     87%
Isobutyric  86%
Pentanoic   86%
Hexanoic    82%

One distillation give 70-90% purity, >95% after two distillations.
Not good for phenylacetic acid due to ring bromination.


Here is another reference

Preparation of a-bromalkanedioic acid, or a-bromalkanoic acids as intermediates for herbicides and growth regulators.
Beska, Emanuel; Konecny, Vaclav.  (Czech.).    Czech.  (1987),     4 pp.  CODEN: CZXXA9  CS  242218  B1  19870915  Patent written in Slovak.

Patent#  CS 242218
Patent Classifications
Main IPC:  C07C055-32.  Secondary IPC:  C07C053-15.

Abstract
The title compds. are prepd. by reaction of alkanoic or alkanedioic acids with Br in the presence of Cl or SO2Cl2 oxidn. agents.  The products are suitable intermediates for manuf. of herbicides and growth stimulators.  A mixt. of AcOH 400, Ac2O 80, pyridine 0.6, and Br 1 mL was heated to 100°.  After decolorizing, a mixt. of Br 393.4 and SO2Cl2 332 g was added.  To return HBr entrained with HCl and SO2, AcOH 260 and Ac2O 50 mL were added dropwise.  After 3 h, the reaction mixt. was cooled, water 30 mL was added, and the mixt. was vacuum distd. to give 192.2 g bromoacetic acid.  The yield was 78.8%. 
 
Here is another one
Kinetics of the acid-catalyzed a-bromination of aliphatic acids.  
J. Org. Chem.  (1978),  43(19),  3684-7.

Abstract
RCO2H (R = alkyl) were easily a-brominated in 78-95% yields by Br2 in ClCH2CH2Cl contg. ClSO3H catalyst at 84°.  The kinetics were 1st order each in Br2 and RCO2H; the rate const. was proportional to the initial ClSO3H concn. at an early stage.  The Taft reaction const. was r* -0.97 at 60°.  The reactivity increases as follows: HOAc < EtCO2H < PrCO2H < Me2CHCH2CO2H < Me2CHCO2H < Et2CHCO2H.  The mechanism involves ketene intermediates. 


This one is messy

a-Halo carbonyl compounds.  I.  Efficient preparation of a-bromo esters and a-bromo acids. 
Tetrahedron Lett.  (1972),   (40),  4067-70.

Abstract
R1CHBrCO2R were prepd. from MeCOCH2CO2R (R = Et, Me3C) by alkylation to MeCOCHR1CO2R (e.g. R1 = Me, Et, PhCH2), followed by bromination of the sodium enolate to MeCOCBrR1CO2R and deacetylation with anhyd. Ba(OH)2 in alc. R1CHBrCO2CMe3 gave the corresponding acid even in the presence of oxygensensitive and acid-base sensitive substituents, e.g. R1 = allyl, 4,4-(ethylenedioxy)pentyl.  The use of alkyl iodides and allyl bromides improved the yields of the alkylation. 

Do Your Part To Win The War

[foxy2]

The preparation of alpha-halogenated carboxylic acid derivatives is normally achieved by refluxing the carboxylic acid with halogen and phosphorous trich1oride.(l) Alternatively, substituted malonic acids may be brominated and decarboxylated to obtain the corresponding a-bromo acids.(2)

1. c.f. H. T. Clarke and E. R. Taylor, Org. Syn., Coll. Vol. 1, 115(1944).
2. c.f. C. S. Marvel and V. duvigneaud, Org. Syn., Coll. Vol. 2, 93(1943).
Do Your Part To Win The War

[megamole]

Rh,

Wow, this was a nice find! Thanks! I just wanted to draw everyone's attention to the fact that alpha-bromopropionic acid can be made very easily in good yields by treating alanine with HBr and sodium nitrite. While the Sandmeyer reaction isn't always so effective on aliphatic amines, alpha-amino acids are an exception. Since alanine is readily available by the kilogram at heathfood stores around the world, this should make nitroethane far more obtainable for everyone.
"Give me ten minutes with your inner child, and I'll give you back an inner adult."

[Rhodium]

Do you have any references or procedures for that alanine reaction?

[megamole]

Rh,

Do I have references or procedures for the alanine reaction?    Ask, and you shall recieve.  

The number of examples of the Sandmeyer reaction used on amino acids is huge, and the reasons for this are pretty obvious. Amino acids are cheap chiral starting materials, and the Sandmeyer reaction allows the chemist to produce a wide array of optically pure intermediates from amino acids for asymmetric synthesis. Because this sort of thing is so ubiquitous in the literature, I've only listed examples of alpha-halo propionic acids being made from alanine, rather than include all the examples of alpha-halogenated aliphatic acids prepared from amino acids.

Bioorganic & Medicinal Chemistry Letters (2000) 10, 17, 2037 - 2040.
Bulletin of the Chemical Society of Japan (1981) 54, 10, 3211-3212.
Bulletin of the Chemical Society of Japan (1989) 62, 8, 2562-2566.
Canadian Journal of Chemistry (1994) 72, 1, 131-141.
Chemistry Letters (1986) 1133-1136.
Farmaco (1994) 49, 9, 587-606.
Journal of Organic Chemistry (1985) 50, 9, 1356-1359.
Journal of the American Chemical Society (1954) 76, 6054,6056 Amn.20.
Journal of the American Chemical Society (1992) 114, 20, 7645-7651.
Journal of the American Chemical Society (1993) 115, 23, 11010-11011.
Journal of the Chemical Society - Perkin Transactions 1 (1987) 111-120.
Journal of the Chemical Society - Perkin Transactions 1 (1988) 3183-3194.
Journal of the Chemical Society - Perkin Transactions 1 (1998) 22, 3767-3776.
Journal of the Royal Netherlands Chemical Society (1980) 99, 3, 96-99.
Russian Chemistry Bulletin (1996) 45, 3, 676-679.
Synthesis (1987) 3, 225-228.
Tetrahedron (1995) 51, 31, 8459-8470.
Tetrahedron Letters (1985) 26, 43, 5257-5260.
Tetrahedron Letters (1987) 28, 17, 1873-1876.
Tetrahedron: Asymmetry (1993) 4, 6, 1141-1152.

There are also a great number of examples of alpha-halo prpionic acids being made from lactic acid, and if you're interested in that, I'd be willing to submit a list of examples of that from the literature as well.

I hope this helps,

-megamole
"Give me ten minutes with your inner child, and I'll give you back an inner adult."

[Rhodium]

Yes, the lactic acid references would also be welcome, thanks megamole!

[lugh]

Emil Fisher's proof of the Walden inversion using the nitrosyl bromide route was originally published in Ber. 40, 489 (1907), taken verbatim from JOC 50, 1357 (1985)  

(R)-2-Bromopropionic acid:
50 g D-Alanine (.56 mol) was dissolved in a mixture of 580 ml of 48% aqueous HBr and 1 L of water, and cracked ice added to give a total volume of 3 L. 104.3 g NaNO2 (1.51 mol ) was added in small portions with stirring, followed by 700 g of Na2SO4. When the stirred reaction had warmed to 15°C, it was decanted from solids and extracted with five 500 ml portions of Et2O. Drying of Na2SO4 and then CaCl2 and concentration in vacuo gave 65 g of oil as residue. this was distilled at 25 torr collecting the forerun between 40-70°C, and three fractions distilling at 104-8°C (25 torr) totalling 51.3 grams.

[megamole]

Rh,

Sorry for taking so long to get back to you.

Here are a couple instances of aliphatic alpha-hydroxy carboxylic acids being converted alpha-halo acids. They're old, but we're not exactly talking about high-tech chemistry with this reaction, are we?

Justus Liebigs Ann. Chem. (1864) vol. 130, Pp. 16.
Ber. (1879) vol.12, Pp. 178.

[megamole]

lugh,

Thanks for submitting the expirimental details for this oh-so-practical Sandmeyer reaction. Folks, if you haven't given it much thought yet, this looks like the simplest, most practical method of preparing alpha-halopropionic acids around! A little alanine, a little HCl, and some sodium nitrite -- how much easier can you get?

...runaway threshing machine at a puppy farm...

[Bozakium]

Great find! Yes, as lactic acid is an easily available precursor this makes another listed goodie available to the masses with a little inginuity. All you lactating women run & hide now....
  As a last resort there is a Bozakium way to lactic acid form dead stuff: Lactic acid is produced in muscles when they lack enough oxygen for the work they are called upon for and begin anaerobic metabolism. It is lactic acid buildup that produces cramps during intense exercise. If one were to, say, chase an animal to exhaustion, then immediately amputate  the legs and diaphram & associated muscles, the lactic acid could be extracted & distilled to purity.I'ts a bit round-about and labour intensive, but it's tough to put exhausted roadkill on the schedule 1 list.......For extra yield, make it a pregnant animal and get that milk. I'm sure the animal rights people will hate me for this, so to be PC, find one that was just chased down and killed by its natural predators, then scare them off. I'm sure the wolves wont mind you stealing a hunk of their fresh caribou......

[Osmium]

Thanks, what a nice procedure for a few millimoles of lactic acid...  

[Bozakium]

It's just nice to know there are alternatives for the insane......    

[cilliersb]

How about this one:

Find an alchoholic, he should have a vitamin b1 deficiency because of his habit. Make him drunk, inject him with pure glucose and he should produce shitloads of lactic acid until he dies from "Lactic acidosis"

Now just extract this from the corpse!

Obviously just kidding guys, but this is what happens if you get too much glucose in your blood and you have a Vitamin B1 shortage.

HeHe

[Rhodium]

Okay, this is fun an all, but please keep this thread on topic and don't post any silly methods using alcoholics or corpses for the preparation of precursors (even if it is very common to use alcoholics to prepare precursors, but usually it is done by themselves, and not by someone else extracting their bodily fluids).