Sciencemadness Discussion Board - nitroethane synthesis question

nitroethane synthesis question

mackolol - 10-4-2020 at 10:28

Nitroethane can be readily synthesised from a-bromopropionic acid, but its synthesis requires pretty lotta bromine.
Can one synthesise nitroethane the same way (from nitrite, bromopropionic acid and magnesium ion) but from 3-bromopropionic acid, which is easily synthesised from available acrylic acid and HBr?

Chemi Pharma - 10-4-2020 at 11:15

At Rhodium Archives in the old Hive, there is a paper written by "Aurelius" titled "Nitroethane Synthesis: A Compilation".

His method number eleven (11) is exactly what you want to know. They use 3-chloropropionic (3-bromopropionic as well) acid sodium salt plus sodium nitrite to do a decarboxylation giving Nitroethane. See:

Nitroethane-11 method-Rhodium.gif - 14kB

[Edited on 10-4-2020 by Chemi Pharma]

clearly_not_atara - 10-4-2020 at 11:22

No. The carboxylate group at alpha position is necessary to suppress the formation of the alkyl nitrite.

(See also the "short questions thread".)

EDIT: Chemi, that is cited as "modification of Orgsyn". This is the Orgsyn:
http://www.orgsyn.org/demo.aspx?prep=CV1P0401
The modification is not very faithful to the source, IMHO.

EDIT2: For details confirming the suppression of nitrite formation in alpha-haloacids see Pritzl and Adkins 1931.

[Edited on 10-4-2020 by clearly_not_atara]

Attachment: pritzl1931.pdf (289kB)
This file has been downloaded 489 times

Chemi Pharma - 10-4-2020 at 11:48

@Clearly,

I'm really not very sure about if this method given by "Aurelius" at Rhodium site works or not. I have my doubts too about the necessity of the halogen bonded in the alpha position or not. As I have this paper since a long time ago I decided to share it, but I agree with you isn't a unsuspicious source.

Thanks for the reference. I will take a read to learn more about that.

mackolol - 10-4-2020 at 13:28

Quote: Originally posted by clearly_not_atara

(See also the "short questions thread".)

EDIT: Chemi, that is cited as "modification of Orgsyn". This is the Orgsyn:
http://www.orgsyn.org/demo.aspx?prep=CV1P0401
The modification is not very faithful to the source, IMHO.

[Edited on 10-4-2020 by clearly_not_atara]

I agree, people from erowid tend to share syntheses full of mistakes, generally theoretical and not checked.
But still I don't see nothing in this article that claims why other than alpha substituted haloacids don't go this reaction.

morganbw - 10-4-2020 at 15:35

@mackolol
I agree with your questions. I doubt that I will live long enough to experiment with perhaps the beta versus the alpha but I have thoughts as well.
I may have a blind spot but some experiments may be in order.
Lots of questions and experiments I wish to do. Running out of years sucks.

clearly_not_atara - 10-4-2020 at 19:31

The problem is that the formation of nitrite esters actually results in the destruction of the formed nitro compound.

RONO + R'(H)NO2 >> ROH + R'(NO)NO2

R'(NO)(NO2) >> 2 NO + R=O etc

The presence of nitrite anion may make matters worse.

RONO + NO2- <> N2O3 + RO-

For some unclear reason using alpha-haloacids prevents the formation of these nitrite esters. Performing the reaction in polyethylene glycol seems to have a similar effect. Silver nitrite in diethyl ether works similarly and does not form any free nitrite anions.

But by "ordinary" alkylation it is extremely difficult to obtain the regioselectivity nitro >> nitrite which is required for an isolable yield.

[Edited on 11-4-2020 by clearly_not_atara]

S.C. Wack - 10-4-2020 at 19:39

If bromine is an issue, use a precursor that uses HBr to introduce the Br. But there will be a tradeoff, some other chemical which you don't want to use will be called for. The compilation
https://the-hive.archive.erowid.org/forum/showflat.pl?Cat=&a...
is simply in error saying 3 instead of 2.

clearly_not_atara - 10-4-2020 at 19:50

Propanal can be made from propylene glycol and halogenated with CuCl2 or CuBr2. Further oxidation with hydrogen peroxide gives the acid. This way is circuitous but it's relatively safe and simple; in theory you could avoid bromine entirely.

edit: e.g.
http://doi.org/10.1016/j.apcata.2011.04.028
http://doi.org/10.1016/j.apcata.2009.07.018

[Edited on 11-4-2020 by clearly_not_atara]

Chemi Pharma - 10-4-2020 at 23:11

Quote: Originally posted by mackolol

Nitroethane can be readily synthesised from a-bromopropionic acid, but its synthesis requires pretty lotta bromine.
Can one synthesise nitroethane the same way (from nitrite, bromopropionic acid and magnesium ion) but from 3-bromopropionic acid, which is easily synthesised from available acrylic acid and HBr?

I didn't realize we are talking about HBr addition to an unsaturated chain.

Adding HBr to acrylic acid you will get the alpha bromopropionic acid, that's your target, and not the beta (3-) kind like you've said, cause the Markovnikov addition rule (selectivity). You don't need to use bromine to get the alpha kind.

[Edited on 11-4-2020 by Chemi Pharma]

mackolol - 11-4-2020 at 00:54

Quote: Originally posted by Chemi Pharma

Oh... I didn't examine the patent by looking into reaction by organic chemistry rules, but I assumed that US patent is telling truth.
Here is it: 3-bromopropionic acid from acrylic acid and HBr

https://patents.google.com/patent/CN1365963A/en

Chemi Pharma - 11-4-2020 at 01:48

Yeah! I don't know why the patent is telling about an anti-markovnikov addition without the use of any kind of catalizer. That's against all the chemical principles I know. I can't explain that!

However, I think you should take a look at another thread here in sciencemadness telling about the synthesis of alpha bromopropionic acid from alanine and HBr and from latic acid and HBr with some kind of variations:

http://www.sciencemadness.org/talk/viewthread.php?tid=3860&a...