P2np Syntheses Ammonium Acetate Catalysis

TucoSalamanca.

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Ammonium Acetate Catalysis in ExcessNitroethane3​

A solution of benzaldehyde (6.4 g) and ammonium acetate (1.0 g) in nitroethane (20 mL) was heated to reflux for 5 h. On cooling, after removal of the solvent, the residue was purified by column chromatography on silica gel 60 N (neutral; hexane-chloroform, 2:1, v/v), then recrystallized from hexane and gave 1-phenyl-2-nitropropene as a light yellow crystals weighing 6.2g (63%), mp 71-73°C.
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There is a synthesis, but what I don't understand is that it is purified by chromatography. What can I do instead? How many degrees will the reflux be? Can you write in detail how to do it?
 

TucoSalamanca.

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Can you write the synthesis in detail? N-Butylamine and cyclohexylamine are not sold in my country, only ammonium acetate is sold.
 

yuiopjkl

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This is my experience with ammonium acetate:
80ml benzaldehyde
80ml nitroethane
60g anhydrous ammonium acetate
70ml GAA

refluxed In a water bath, the temperature is close to boiling (I think 90°-95°) for 5-6h.

Shake the flask periodically
ZekCSvy5UR


After 6h:
D4nSseXPFW


Let it cool to room temperature and place it in the freezer.
Yield is 78g.


note:
- If it does not crystallize, place a rod in the mixture.
-If you have ready-made P2np, put some of it in the mixture and it will crystallize immediately.

-Use dry ammonium acetate (My ammonium acetate was very wet and I dried it as much as I could with tissues, I think this is the reason for the low yield).
Thanks to the experts for the help
@G.Patton @HIGGS BOSSON
ZGRfK4uX6A
 
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Rabidreject

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Thanks VERY much for this!! I can’t believe i have had all the precursors I need for one of the most simple RXN’s and didn’t even realise it!!
I really appreciate you steering me to this post!!!
Can you dry the ammonium acetate by any other method such as maybe dissolving into something to treat with anhydrous MgSO4? Just a thought, as yes I can buy anhydrous ammonium acetate but it’s quite a bit more ££.

I must admit i am having issues with regards crystallisation of the final n,n-DMT product, having used NaBH4.

I need another project to distract me from the fact I’m failing! Ha
I did get SOME DMT, but yields are unacceptable atm…

the synth says to re-x the final oil from boiling heptane but mine refuses to have anything to do with each others seperate layers! It’s v annoying.
I currently have a fridge full of methanol and formaldehyde in prep to try it again - I KNOW at points it went above 0c and know that’s not good!
 

yuiopjkl

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Ammonium acetate is easier to synthesize than to dry, so it is better to buy it anhydrous.

I was looking for a way to dry it, but I couldn't find a way that worked for me
 

Rabidreject

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I FINALLY actually got round to trying this, it’s under reflux now actually - colour is getting there for sure!
I fucking hate the smells you get from putting this rxn together…I really dislike that almonds cherry smell that this aldehyde releases, it’s gross - also is a really heavy liquid.

Mind you at least it’s legal here…is it not restricted in the states? I remember watching that ‘positive meth amphet‘ episode of Hamiltons show where he had was it uncle fester? It was def one of the chemists who has written lots of books on this subject and he was synthesising benzaldehyde or trying to at least - don’t see why he would try that if you could just buy it like here….might be wrong tho…either way it fucking stinks!

And yes. The ammonium acetate is a little bit of a bitch to work with -I honestly just got a knife, stabbed the 250g tub and then picked out whole chunks of it and prodded it into a funnel in the flask.
its weird stuff though, it actually really reminded me of ice…not meth-amphet’s street name but regular, cold snow balls type ice 🧊 odd stuff but I was hoping it would all melt together when heated - I was correct Bug yeah I’d try and buy it anhydrous next time - even though I accidentally bought like a kilo and a half of the stuff by accident!

cheers for the guide anyway - seems similar-ish to the nitroaldol rxn I was doing on 2,5-DMOBA only using a mad catalyst and WAY MORE nitroethane than nitromethane, however, I guess that’s the trade off for not having any n-butylamine, I guess…I much prefferred having the correct catalyst tho - ethylenediamine in the case of the 2,5-DMOBA…

hopefully it shall work….no idea how ill go about reducing it even if I do manage to crystallise something and don’t end up with some shitty annoying oil…

by the way, I’m getting into the rxn now and no…total wrong colour…. Bright red! Bah!
 

Rabidreject

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Ummmmm….weird colour - I’m highly doubtful over this 🤨
NHtQuKrhE9
 
Last edited:

G.Patton

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Recrystallization. There is topic with detailed video tutorial, write up and wide discussion in comment section. Just look around BB Forum before make a new post with the same issue, which is very common and already discussed and described billion times.
 

PHDorganic

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80ml benzaldehyde
80ml nitroethane
60g anhydrous ammonium acetate
70ml GAA

this will not work.... so if someone reads this dont waste your time and chemicals!
 

TheCook

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Then just give me one good reason why that shouldn't work?
 

PHDorganic

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Given the traditional Henry reaction, and given this ratio: Benzaldehyde 1000 ml, nitroethane 1000 ml, glacial acetic acid 250 ml and n-butylamine 50 ml

Explanation:

  1. Benzaldehyde (C6H5CHOC6H5CHO):
    • This aromatic compound provides the benzene ring and an aldehyde group.
  2. Nitroethane (CH3−CH2−NO2CH3−CH2−NO2):
    • Contributes the nitro group (-NO2).
  3. Acetic Acid (CH3−COOHCH3−COOH):
    • Acts as a weak acid catalyst and provides an acetyl group.
  4. n-Butylamine (C4H9NH2C4H9NH2):
    • Functions as a base in the reaction.
  5. Product (Phenyl-2-nitropropene):
    • The main product formed is Phenyl-2-nitropropene.

Let's break down the reaction for the formation of Phenyl-2-nitropropene from the given reactants:

Step 1: Nucleophilic Addition of Nitroethane to Benzaldehyde

  1. Formation of the Enamine Intermediate:
    • n-Butylamine (C4H9NH2C4H9NH2) reacts with benzaldehyde (C6H5CHOC6H5CHO) to form an enamine intermediate.
    • The lone pair of electrons on the nitrogen atom of n-butylamine attacks the carbonyl carbon of benzaldehyde, resulting in the formation of the enamine.
\ceC6H5CHO+C4H9NH2−>C6H5CH=CH−NH−C4H9\ceC6H5CHO+C4H9NH2−>C6H5CH=CH−NH−C4H9

Step 2: Nitroethane Addition to the Enamine

  1. Nitroethane Addition:
    • Nitroethane (CH3−CH2−NO2CH3−CH2−NO2) adds to the enamine intermediate through a nucleophilic addition reaction.
    • The nitronate ion attacks the enamine, forming a new carbon-carbon bond and generating the nitroalkane intermediate.
\ceC6H5CH=CH−NH−C4H9+CH3−CH2−NO2−>C6H5CH=CH−NO2+C4H9NH2\ceC6H5CH=CH−NH−C4H9+CH3−CH2−NO2−>C6H5CH=CH−NO2+C4H9NH2

Step 3: Formation of Phenyl-2-nitropropene

  1. Dehydration and Formation of Phenyl-2-nitropropene:
    • Acetic acid (CH3−COOHCH3−COOH) reacts with the nitroalkane intermediate, leading to the elimination of water (dehydration) and forming Phenyl-2-nitropropene.
\ceC6H5CH=CH−NO2+CH3−COOH−>C6H5CH=CH−NO2+H2O\ceC6H5CH=CH−NO2+CH3−COOH−>C6H5CH=CH−NO2+H2O

Overall Reaction: \ceBenzaldehyde+Nitroethane+AceticAcid+n−Butylamine−>Phenyl−2−nitropropene+OtherProducts−>\ceBenzaldehyde+Nitroethane+AceticAcid+n−Butylamine−>Phenyl−2−nitropropene+OtherProducts

Key Points:

  • The reaction involves multiple steps, starting with the formation of an enamine intermediate.
  • Nucleophilic addition and dehydration reactions contribute to the synthesis of Phenyl-2-nitropropene.
  • Reaction conditions, such as temperature and concentrations, influence the outcome, and optimization may be required for optimal yields
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Given the variant of the Henry reaction, and given this ratio: 80ml benzaldehyde 80ml nitroethane 60g anhydrous ammonium acetate 70ml GAA

I wont rewrite the reaction mechanism as we should assume it is the same?

Substituting n-butylamine with ammonium acetate in the reaction you provided would significantly alter the reaction pathway. Ammonium acetate typically acts as a catalyst in some reactions but does not serve the same nucleophilic function as n-butylamine. The reaction would likely follow a different mechanism, and the final product could differ.

Here's a brief overview of the expected changes:

  1. Formation of the Enamine Intermediate:
    • Instead of a nucleophilic attack by the lone pair of nitrogen in n-butylamine, ammonium acetate may facilitate the reaction differently. The reaction mechanism would depend on the specific conditions.
  2. Nitroethane Addition to the Enamine:
    • The addition of nitroethane to the enamine intermediate might still occur, but the details of the reaction would be influenced by the nature of the intermediate formed with ammonium acetate.
  3. Formation of Phenyl-2-nitropropene:
    • The dehydration step involving acetic acid may still occur, but the specifics could vary, and the overall outcome might produce different by-products or isomers.
Balancing the reaction with ammonium acetate would require a detailed understanding of the specific reaction conditions, concentrations, and mechanism, which may not be readily available without experimental data. i will run the numbers again after posting this in case i am wrong.

In summary, while ammonium acetate can play a role in some reactions, substituting it for n-butylamine in the given context would likely result in a different reaction pathway and possibly a different final product. Detailed experimental investigation and optimization would be needed to determine the specific outcome.

Lets further investigate and see if you can find any reason it should work?


This is the values for
n-Butylamine
Acidity (pKa)0
Basicity (pKb)3,2

This is the values for Ammonium Acetate
Acidity (pKa)9.9
Basicity (pKb)33

n-butylamine might not work or could lead to different outcomes:

  1. Difference in Reactivity:
    • n-Butylamine is a primary amine with a nucleophilic amino group, allowing it to participate in nucleophilic addition reactions. Ammonium acetate, being a salt, lacks a nucleophilic amino group. Its reaction behavior may involve proton transfer or catalytic activity rather than direct nucleophilic attacks.
  2. Role of Ammonium Acetate:
    • Ammonium acetate is often used as a catalyst or for facilitating certain reactions through its acidic or basic properties. However, its specific role depends on the reaction conditions and the nature of the reactants. In the provided reaction, the absence of a nucleophilic group in ammonium acetate may limit its direct involvement in certain steps.
  3. Reaction Mechanism:
    • The substitution of n-butylamine with ammonium acetate could alter the overall reaction mechanism. The nucleophilic attack, which is crucial in the formation of the enamine intermediate, might not proceed as expected with ammonium acetate.
  4. By-Products and Side Reactions:
    • Different reaction pathways may lead to the formation of alternative by-products or side reactions. The selectivity and efficiency of the reaction may be influenced by the specific reagents and conditions.
  5. Optimization Challenges:
    • Even if a reaction involving ammonium acetate were possible, achieving optimal yields and selectivity might require extensive optimization of reaction conditions such as temperature, concentration, and reaction time.
  6. Balancing the Equation:
    • Substituting ammonium acetate might also necessitate adjustments to the reaction stoichiometry to balance the equation. This depends on the specific reactions that ammonium acetate undergoes under the given conditions.
In essence, the choice of a reaction partner is critical in organic synthesis, and each reagent contributes distinct functional groups and reactivity patterns. Without experimental data or specific details about the reaction conditions, it's challenging to predict the exact outcome of substituting ammonium acetate for n-butylamine in the given reaction. Experimental testing would be required to explore the viability of this substitution and understand the resulting chemistry.

See attatchments and see if you can make sence of it. i cant. the numbers dont add up the differens in buffur solution, and what is it acting as a catalyst for? dont get me wrong, i accualy hope i am wrong here, because it is way cheaper and easyer to make Ammonium Acetate, then n-butylamine, thats for sure.
 

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TheCook

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Hi!

This is not correct, as you are only comparing ammonium acetate with n-butylamine. The difference is the combination of ammonium acetate in acetic acid. Ammonium acetate is hygroscopic (therefore it has a tension to dissociate only by presence of the undried solvents or air vapours) and dissociates in solution to form ammonium ions NH4+ and acetate ions (OAc-).
The acetate anions act as weak bases. In the reaction, they form an equilibrium with the protons of acetic acid, creating a slightly alkaline environment. The ammonium ion also contributes to the equilibrium, but not to catalysis.
Here is what happens:
First the dissociation of the Ammonium Acetate (Traces of water in the solvents are usually sufficent to solvate some of the ions). Because water is produced in the reaction, it could be used to solvate more Ammonium Acetate:

NH4OAc <-> NH4+ + OAc-

Nitroethane is activated by the basic environment provided by the acetate ion, forming a nitronate anion:

CH3CH2NO2+OAc-−>CH3CHNO2−+HOAc
Here, nitroethane reacts with an acetate ion to form a nitronate anion and release acetic acid.

The nitronate anion then attacks benzaldehyde to form the nitroalcohol intermediate:

C6H5CHO+CH3CHNO2 -> C6H5CH(OH)CH2NO2C6H5CHO+CH3CHNO2−>C6H5CH(OH)CH2NO2

Finally, dehydration occurs to form P2NP and water:

C6H5CH(OH)CH2NO2 -> C6H5CH=CHNO2 + H2O

Sometimes some of the Ammonium ions could be deprotonatet, but they are protonated again by the actetic acid.


Regards
 

PHDorganic

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Thank you! i will give it a try. it makes more sense now. it on paper looked at first glance that it would not be able to keep the reaction going, but i assume one has to be exceptionally curtain that every thing is anhydrous and that the GAA is in fact 99% and not 90+ as the hydration of the amine salt would be saturated before the process is completed, or to be honest i thought at first when i saw it that ammonium acetate could even facilitate the reaction. but again nothing is greater then learning something new and especially when it also makes life easier. So again thank you!
 

OrgUnikum

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This is the worst way to run the Henry reaction to make P2NP from Benzaldehyde and Nitroethane. Lousy yields and a dark mess which is hard to workup. There is neither place nor reason for this crap to even be considered a useful candidate for this reaction.

Be warned! Stay away! A big waste of precursors and time, the only compound this synth produces in excellent yields is unhappiness.
 
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PHDorganic

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whats your reasoning to conclude this? i ask of curiosity as this was initially my first thesis?

G.Patton​

William Dampier​

i sincerely apologize bringing you guys on on this topic, can you assist on this matter?​

 

yuiopjkl

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Ammonium acetate is the best option if you cannot obtain cyclohexylamine.
The yield is not bad and the product is not very dirty. It only needs to be recrystallized once.
The last time I did the synthesis the yield was 100g from 90ml Nitroethane.
I haven't recrystallized it yet
NeZIy1O8s7
 
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PHDorganic

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That does not look good, it has wrong crystalline form, and color. you even sure this is p2np? in case dont use it it looks poisonous
 

yuiopjkl

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90ml nitroethane,90ml benzaldehyde,70ml GAA and 70g ammonium acetate.
The details were previously written above.
 

yuiopjkl

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Because I haven't crystallized it yet.
 

OrgUnikum

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Take any bulky amine dissolve in a little IPA and add GAA until ph is acidic. This si your catalyst. Yes it will not be dissolved in the IPA but it does not matter. 10 g Amine per 100 ml Benzaldehyde is enough one can use less and get great yields just nuke two times more in the micro to 60°C max. Mix nitro and benzaldehyde and add a part of the catalyst, stir, nuke let cool down and repeat. I never had anything below 90% yield and I used a whole assembly of different amines. You must not look to get the one and only amine but you must look which amines you can get easily and then see which works best.
 
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