nitroalkane synthesis, via KMnO4 + alkylamine

mk-1 · Mon May 23, 2005 8:31 pm

Hi there.
Ive recently come across a reaction in OrgSyn describing the preparation of 2-METHYL-2-NITROSOPROPANE via the oxidation of tert-butylamine with KMNO4 to and subsequent reduction with Al/Hg and reaction with NaOBr.
From this the most important part for me, is the nitroalkane synthesis from alkylamine, since where I live, nitro compounds are highly forbidded due to terrorism.

so, from OrgSyn :
"2-Methyl-2-nitropropane. To a well-stirred suspension of 650 g. (4.11 moles) of potassium permanganate in 3 l. of water, contained in a 5-l., three-necked flask fitted with a reflux condenser, a mechanical stirrer, a thermometer, and a 250-ml. dropping funnel, is added, dropwise and with stirring over a 10- minute period, 100 g. (1.37 moles) of tert-butylamine (Note 1). When the addition is complete, the reaction mixture is heated to 55° over a period of approximately 2 hours, and maintained at 55° with continuous stirring for 3 hours. The dropping funnel and reflux condenser are replaced with a stopper and a still head fitted for steam distillation, and the product is steam distilled from the reaction mixture (Note 2). The liquid product is separated from the denser water layer, diluted with 250 ml. of diethyl ether, and washed successively with two 50-ml. portions of 2 M hydrochloric acid and 50 ml. of water. After the ethereal solution has been dried over anhydrous magnesium sulfate, the solution is fractionally distilled at atmospheric pressure, removing the ether. The residual crude product (Note 3) totals 106–128 g. and is sufficiently pure for use in the next step. In a typical run, distillation of 124 g. of the crude product affords 110 g. (78%) of the pure 2-methyl-2-nitropropane as a colorless liquid, b.p. 127–128°, n25D 1.3992, which slowly solidifies on standing to a waxy solid, m.p. 25–26° (Note 4).

Notes
1. tert-Butylamine, purchased from Aldrich Chemical Company, Inc., may be used without purification.
2. Approximately 1 l. of distillate needs to be collected to remove the product from the reaction mixture.
3. The principal contaminant is residual ether.
4. The purified product exhibits IR bands (CCl4) at 1545 cm.−1 (broad) and 1355 cm.−1 (NO2) with a UV maximum (95% C2H5OH) at 279 nm (ε 24) and a 1H NMR (CCl4) singlet at δ 1.58 [(CH3)3C]. The mass spectrum has the following abundant fragment peaks: m/e (rel. int.), 57 (100), 41 (74), 39 (45), and 29 (57)."

So, i think a typical method to get nitroalkane, in this case nitromethane would be -
3mol KMnO4 is dissolved in 1-1.5L, and stirred. 1mol Alkylamine in around 100-200ml of water (aq. methylamine) is slowly added to the solution, while stirring. A reflux condenser is fitted, and the solution is slowly heated to 55degC, and then kept at this temp for 3 hours, with stirring.
Then a distil head is fitted, and the reaction mixture is distilled. then the product is mixed with ether and the water layer discarded. then the mixture is washed with 2N HCl, and then with water, and then dried over MgSO4. Later the ether is distilled away, which leaves crude nitromethane. this can be distilled to purify or maybe used without purification in the next steps of any reaction.

any notes or flames are welcome Very Happy

ApprenticeCook · DILLIGAF

the production of nitro compounds from amines with permangenate is well noted on rhodium mirrors... have a look on the nitroethane synthesis faq under organic synthesis methods on the rhodium mirror.

-AC

Carbon13 · Tue May 24, 2005 10:03 am

This will only work for a primary amine at a tertiary carbon.

brain · Linguist Extraordinaire

so to make thic clear Smile

.... ethylamine --kmno4--> nitroethane?

mk-1 · Tue May 24, 2005 12:35 pm

yes brain, to make it clear ethylamine + KMnO4 => nitroethane.
just remember to use a 3/1 mol ratio KMnO4/Amine

IndoleAmine · Dreamreader Deluxe

ethylamine is no primary amine with "tertiary carbon" - it has only two, so only secondary and primary... ( Question

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