Author Topic: Easy nitroethane in quantitative yield  (Read 10211 times)

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halfapint

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Re: Easy nitroethane in quantitative yield
« Reply #20 on: January 21, 2002, 08:05:00 AM »
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

(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>>

Aurelius

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Re: Easy nitroethane in quantitative yield
« Reply #21 on: January 21, 2002, 09:42:00 PM »
Alanine- health food store
Lactic acid- aurelius is sure that it can be had cheaply
propionic acid-  haloform rxn with MEK/hypohalite

all pretty cheap and easy to obtain

stick with alanine and lactic acid though- it eliminates having to carry out another rxn (tedious work)


moo

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alpha-bromopropionic acid from lactic acid
« Reply #22 on: August 19, 2002, 12:49:00 AM »
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

(yellium: "At our labs, old German chemistry was often ...", Methods Discourse)

mellow

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Lactic acid
« Reply #23 on: August 25, 2002, 01:50:00 AM »
Lactic acid - was available from wine-makers a few years ago.

I think it is added to wine to give a lactic acid flavor.

Lactic acid fermentation is a secondary fermentation that sometimes takes place in the bottle - so that the wine becomes sparkling. I think Vino Verde is an example of a wine that undergoes such fermentation.  So basically head down to the wine-makers (to buy it) rather than the yogurt makers (to make it).

moo

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And one more thing
« Reply #24 on: September 01, 2002, 03:54:00 PM »
The Ber. (1879) vol.12, Pp. 178. ref contains no information regarding the production of alpha-bromopropionic acid.