Patent US4319059 (http://l2.espacenet.com/dips/viewer?PN=US4319059&CY=gb&LG=en&DB=EPD)
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 SN2 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)
(http://themerckindex.cambridgesoft.com/TheMerckIndex/NameReactions/ONR180.htm) reaction, or by HBr bromination of lactic acid (?-hydroxypropionic acid).
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000212002-file_3j5o.gif)
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.
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 203.5o.
turning science fact into <<science fiction>>
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..."
I want to round up the approaches to alpha-brominated propionic acid. Can we get any concensus on what is most easily facilitated? Starting with alanine or lactic acid seems seems energetically favorable to brominating propionic acid directly. megamole gave a list of literature for alanine conversion, but since I'm not in range of a chem library the dates and citations show me little. lugh's abstract of one of these looks very promising:
(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 degrees 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 degrees C, and three fractions distilling at 104-8 degrees C (25 torr) totalling 51.3 grams.
Now I don't object to using sodium nitrite twice in the same synthesis (once for the nitrosyl bromide, then again to make nitroethane) but we don't need stereoselective processing. Usually if we buy alanine, we also pay for its being a stereospecific isomer. Also Fischer seems to use a whole lot of reagents to process 50 g of alanine. Why 700 g of sodium sulfate, it's too much.
Another contributor, foxy2, produced some interesting references from propionic acid, one or two of which look reachable. Bromine and PCl3 in a refluxing chlorinated solvent looks OK -- after making PCl3. (The alternative of bubbling with chlorine is also facile.)
In Post 227794 (https://www.thevespiary.org/talk/index.php?topic=9255.msg22779400#msg22779400)
(megamole: "Re: Easy nitroethane in quantitative yield", Methods Discourse) megamole said, in reference to lactic acid:
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.
If Liebig could do it, I can too, but it would help to know just how Liebig did it. Are we talking about a water solution of dl-lactic acid and ~1.5-3.0 equivalents HBr, in which alpha-bromopropionic acid would be left in the still when the more volatile components were boiled out, after an appropriate reflux? I want to hear other beez confirm my judgment that yes, lactic acid is actually simplest to use. I can make calcium lactate in a bucket, which means lactic acid is practically free. It isn't robust, for it won't stand up to ambient pressure distillation, but being free makes it particularly valuable.
So who has preferences among alanine, lactic acid or propionic acid as the starting point for making alpha-bromopropionic acid?
turning science fact into <<science fiction>>
Here it is, needs translation though. It seems this article also suggests a way to produce ethyl 2-bromopropionate.
Justus Liebigs Ann. Chem. 130, 16-17 (1864):
2) Einwirkung von Bromwasserstoffsäure auf Milchsäure
Wird Milchsäure in einem Strom von gasförmiger Bromwasserstoffsäure erhitzt, zuletzt bis 180°C bis 200°C, so destillirt etwas Brompropionsäure über. Weit vortheilhafter ist es, Milchsäure mit etwas mehr als dem gleichen Volum kalt gesättigter Bromwasserstoffsäure in zugeschmolzenen Röhren zwei bis drei Tage im Wasserbad zu erhitzen. Das Product wird dann zweckmäfsig mit alkoholfreiem Aether geschüttelt, die Aetherlösung abgehoben und nach Verdunsten des Aethers destillirt. Bei Rectification des über 180°C übergehenden Antheils erhält man bei 202°C bis 204°C reine Brompropionsäure. Die niedriger siedenden Theile enthalten schon viel Brompropionsäure, die durch nochmalige Rectification zum Theil gewonnen werden kann. (In dem bei 197°C bis 200°C siedenden Theil wurden bei verschiedenen Bestimmungen 50,8 pC. Brom gefunden.)
Beim Oeffnen der Röhren bemerkt man bisweilen einen starken Druck; das entweichende Gas ist reines kohlenoxyd, ohne Beimengung von Kohlensäure. Wird der Röhreninhalt direct destillirt, so gehen mit den Wasserdämpfen einige Tropfen einer bromhaltigen, angenehm riechenden Flüssigkeit über, deren Natur nicht mit Sicherheit festgestellt werden konnte. Vielleicht zerfällt ein Theil der Milchsäure nach der Gleichung:
C3H6O3 + 2 HBr = C2H4Br2 + CO + 2 H2O
Wendet man zum Ausziehen des Productes käuflichen, also alkoholhaltigen Aether an, so erhält man bei der Destillation viel Brompropionsäureäther und fast keine Säure; offenbar weil die Brompropionsäure bei Gegenwart von Bromwasserstoffsäure sehr leicht ätherificirt wird.
Post 338035 (https://www.thevespiary.org/talk/index.php?topic=9794.msg33803500#msg33803500)
(yellium: "At our labs, old German chemistry was often ...", Methods Discourse)