n-butylamine condensations

Bumblebee · Sat Apr 02, 2005 3:43 am

We tried Tetraedr´s Reaction using GAA and n-Butylamine.
It was our first attempt to do a Nitroethane/benzaldehyde condensation ever.

icecool · Insistent Chemist

You have got the right crystals.
They do look a bit yellowish so recrystalizing wouldn't hurt.
And the maximal yield is x so you devide your amount threw x and then multiply with 100%.
So if the x would be 50g then you do (21g/50g)*100% = 42% yield.
The maximum was in this thread somewhere.
Anyway it is a very good yield if you ask me don't remember the max exactely but it was around 23g or 28g or so...
SWIM will also use a bit GAA when making P2NP.
And the P2NP won't stick with the water and if so that wouldn't matter since the water will melt eventually and the P2NP doesn't dissolve in water and it won't go in the water anyway because it doesn't dissolve in it.
And I would for an even better yield reflux this one longer and dry all the reactans before adding them together.
Since you sayd you drained of some benzaldehyde that didn't react.
I'm suprised you still get a that good yield normally when you reflux longer all the benzaldehyde should react with the nitroethane...

Bumblebee · Sat Apr 02, 2005 5:09 am

The original color of the cristals is not so yellow as on the picture... i just don´t got it better with that camera in my lowtechmobilephone Laughing

I will recrystallize anyway. Purity is never false i think.

is this slightly teargassing effect allright or is there something wrong. i got the feeling this sublimates to the air, leaving this (not bad) smelling "irritating gas"

I´m happy! that is a lot of product for 2 hours of work! Now i have to learn more about reducing that thing.

Yield calculated:
IndoleAmine said 27,45g is 100% you can get (in theory)
but this was meant to 13g Nitroethane and 17ml Benzaldehyde and 3,3ml n-Butylamine
i had 21,2 from tetraedr´s conditions...
btw: whats the molar weight of P2NP?

IndoleAmine · Dreamreader Deluxe

P2NP has a mw of 163.17g/mol.

BzCHO has a density of 1.045g/ml at 25°C, and a mw of 106.12g/mol.

You used 18ml of benzaldehyde, that's 18.81 grams or 0.17725 mol.

Theoretical 100% conversion of all benzaldehyde would mean 28.92 grams of P2NP.

I doubt that your P2NP is dry, since you got 73% conversion(!).

Advice: let it sit at room temp. for one or two days with good ventilation (yes, the fumes ARE nasty, compounds with that tear gas effect are usually called a "lachcrymator"...), and it will dry by itself, and become very light and somewhat "crispy", and you will be able to break/crunch the crystals very easily if they're really dry.

Then do the calculations for yourself, and report back your yield in percent of theory, calculated from the limiting reagent benzaldehyde... Wink

(usually 65-70 percent at most)

For a crude melting point test, put some well ground-up crystals in a test tube, attach a thermometer to the test tube from the outside so that the thermometer bulb is exactly at the end of the test tube, where the crystals are sitting. Then immerse this thing into a beaker filled with cooking oil and a small magnetic stirbar, and place on hotplate stirrer. Start heating the oil slowly, and watch the temp. closely if it approaches the 50°C mark. As soon as the crystals start to melt, you take your first temp. reading, and as soon as everything has melted, you take the second reading. Now you have someting like "60°C-65°C", this is your melting point/range. With P2NP, it can be as high as 71°C when ultra-pure and white/yellowish, and as low as 55° when impure and ugly orange-red.

If you still have the same weight after drying, then congrats - sounds like a extraordinarily high yield then!

i_a

brain · Linguist Extraordinaire

I have some questions about the conditions of these condensations.
-the jar-in whih it condensates have to be closed (oxidation of benzaldehyde's)?
-can it be doed in exicator (with dryind reagent) maybe add to solution silicagel? will suck water and yelded up reaction ?

brain · Linguist Extraordinaire

hm, i dont tkink that you will proceed this condensation in open jar .... ? what are you doing this?

IndoleAmine · Dreamreader Deluxe

It depends on the rxn conditons (temp./solvent) and catalyst used.

For n-butylamine catalysed henry rxns (like decribed here), I use a 250ml RBF with a dean-stark trap and double surface condenser.
For EDDA room temp. condensations in alcoholic solvent I use just a 300ml wide-mouth Erlenmayer flask, and for amm.acetate/alcohol at reflux I use just a RBF and condenser.

Adding silica gel speeds up the rxn definitely, maybe letting it sit in a dessicator for several days helps too (but I don't know).

i_a

brain · Linguist Extraordinaire

I have dean-stark water trap, but i thint that eweryone-dont have this, so silicagel will be then the best way, add silicagel and "reflux"... ?

IndoleAmine · Dreamreader Deluxe

Yes, that will dehydrate the rxn quite effectively and is therefore surely of advantage.

icecool · Insistent Chemist

What would happen if you add insted of 42,5ml benzaldehyde and 33ml nitroethane and 80ml toluene and 8,2ml n-butylamine and equimolair GAA.

Insted of using 8,2ml n-butylamine you used 13,2ml n-butylamine and as much mols as that presents GAA.

So to make it simple what if you use more n-butylamine...

icecool · Insistent Chemist

What would happen if you add insted of 42,5ml benzaldehyde and 33ml nitroethane and 80ml toluene and 8,2ml n-butylamine and equimolair GAA.

Insted of using 8,2ml n-butylamine you used 13,2ml n-butylamine and as much mols as that presents GAA.

So to make it simple what if you use more n-butylamine...

Bumblebee · Wed Apr 20, 2005 6:46 am

i tried the reaction again with good yields.
i did just refluxed the mixture without removing the H2O builded....
the water in the reaction mixture apeared as a white "bubble" in the yellow solution when i turned off the stirrer.
I don´t really understand what that water will hurt in this reaction? even for post-rxn and crystallizing in the freezer it wouldn´t hurt since the crystals are somewhat insoluble in H2O... (don´t know how to get rid of those stinking chrystals in the sink Laughing

)
what does this water do if i let it remain in the reaction? What will increase yield if i remove water in the reaction?
BB

icecool · Insistent Chemist

SWIM tried to concentrate the mixture after the reaction was done and now the mixture got dark red.
Insted of nice orange.
Normally after you filtered out the crystals you concentrate it right...
So SWIM thought it wouldn't be bad to concentrate it immediately after the reaction.

IndoleAmine · Dreamreader Deluxe

Normally you concentrate under vacuum... Wink

(and molten p2np IS dark red, btw)

It was proven several times that yield will increase if you remove water during the rxn, but once the p2np has been formed and the catalyst removed, H2O can't hurt anymore. I was wrong on that.

i_a

icecool · Insistent Chemist

SWIM just got a first crop yield from this reaction with 42,5ml BzCHO and 33,3ml EtNO2 and 13ml n-butylamine and 7,5ml GAA.
The 1st crop weighed: 46,83g --> 68,6% yield so far.
SWIM already concentrated the mixture before putting it in the fridge so he doesn't suppose there will be a lot crystals left in the solution.
The crystals have been drying for 16 hours under a warm lamp.