n-butylamine condensations

IndoleAmine · Dreamreader Deluxe

Tehe - you can tell your SWIM that it is certainly NOT "that easy", posessing the knowledge doesn't automatically mean you have the skills, reagents and apparatus - or every dontknowjack would be "making drugs" all the time... Exclamation

(and it is NOT allowed and can bring you into jail! Don't never ever attempt it, unless you have a grant to do so!)

To "get the hang of how it works", I would suggest that you maybe should stick to plain p2np only first - and when you're familiar with this compound, you will surely extend your knowledge to other interesting molecules....

(You see what cold IPA washes can do to improve purity of p2np? Wash it next time, cleaner is always better....)

greets

i_a

icecool · Insistent Chemist

SWIM will today wash all the P2NP crystals until they are light yellow to white with hot IPA.
And SWIM will definatelly stick to P2NP for a while but when that really works good, then he will try other molecules.

IndoleAmine · Dreamreader Deluxe

Good. But better tell SWIM to use ice-cold IPA, because hot alcohol will dissolve several times as much p2np than cold IPA can; and if you use hot IPA, you'll probably wash away most of your product.

The idea behind this washing is that you dissolve just a very thin outer surface of the p2np crystals, while the very pure inner crystals stay mostly untouched. But the outer layer (containing most of the impurities) is washed away by the IPA, and because you use cold IPA, you wash away only a very thin surface, leaving most of the p2np in its pure form.

If done right and the correct solvents are choosen, the result may look like that some day (note that this is NO 1-phenyl-2-nitropropene, but 1-phenyl-2-methylaminopropane.HCl - and that the outer crystal layer was washed away by rinsing with cold MeOH, then 9:1 Et2O/MeOH, followed by 9:1 Et2O:acetone and finally with a little anhydrous Et2O....):

(please use the "thumbnail" link instead of the file itself when uploading large images, the only difference is that you have to place "th" between filename and extensions, like sample.gif becomes sample.th.gif... ...and it looks simply better!)

i_a

icecool · Insistent Chemist

Should SWIM put the hot IPA with P2NP dissolved in it, in the deep freezer or is room temperature good enough?
And what about adding activated charcoal to get rid of the color?

icecool · Insistent Chemist

Okay SWIM did his second crop filtration and got 8g and the first crop 6g.
And in total he has got exactely 14,03g of P2NP.
And he was wondering about activated charcoal is it nesecarry and is it also combinable with IPA and when cooling down do you do that to roomtemp, or deepfreeze and will the impurities dissolve in the IPA or will you need to filter them off?
If they are dissolved in there won't there also be quite a loss of P2NP in the IPA that goes threw the filter since that is still full of P2NP.

IndoleAmine · Dreamreader Deluxe

Activated charcoal isn't necessary here, P2NP likes to crystallize in a very pure form already by itself, so you don't have to crush up the needles with a mortar, dissolve in hot solvent, boil with decolorizing carbon, filter, concentrate and cool (which is the standard process of cleaning through crystallization) - it suffices to dissolve in just enough hot IPA (to minimize losses, you mustn't use too much here!), and cool down slowly.

Good idea would be to first let it cool to room temp., then put in fridge, and when it is cool, put it into your deep freezer until ice-cold.

The colder the IPA is, the less P2NP it can dissolve, so you will want to let it become as cold as possible for as long as possible to get out most of the p2nP.

But you are right: there are always small losses, thats the drawback of cleaning through recrystallization in general. But since P2NP is only sparingly soluble in ice-cold IPA, the losses are really small (maybe 5% of total yield) - small enough to justify the much greater purity that is achieved through cleaning....

(yep, the impurities stay dissolved in the IPA, even if it is ice-cold. The filtrate looks a lot more reddish than the p2np, didn't you notice that? Thats the trick of the whole thing! Wink

And it would be a good idea to wet the filter paper with a little water/IPA mixture before pouring your P2NP crystals into the buchner, then the filter paper won't be saturated with product after filtration, even less losses this way)

BTW you got 14.03 grams P2NP, in theory and under 100% optimal conditions (which CANNOT be accomplished!), you should've got 27.45grams of P2NP, so you have a yield of 14.03g / 27.45g = 0.51118 or 51.12 percent of theory - not bad, not bad...

** And it is always a good idea to prepare a certain amount of intermediate product when attempting multiple-step snytheses, because if you make any error, you don't have to start synthing the intermediate from scratch again, instead you can work with small amounts you take from your stockpiled intermediate, until you find a nice method for the 2nd step of your synthesis. The advantage is that you work longer with one type of rxn, and can get more familiar with it, plus you don't have to change/clean your glassware/setup and way of thinking very often, and can concentrate on the essential details.....
(this applies to every multiple-step synthesis BTW!) **

i_a

icecool · Insistent Chemist

Thanks a lot for the info, what is the practical 100% yield, that is in organic chemistry the most important since when theoretically 100% never can be achieved one wants to compare to the highest yield ever achieved.
Like cinnamaldehyde from x g benzaldehyde and y g acetaldehyde z g cinnamaldehyde will be prepared theoretically.
But in practical the maximum that is ever achieved in the literature is 80% of z g.
So then you use that as 100% to compare how well you did it.

icecool · Insistent Chemist

What is the practical yield?
Like what is in the literature the maximum one has ever achieved.
Normally you compare that when 100% is not realistic.
And thanks a lot for the recrystalization info.

IndoleAmine · Dreamreader Deluxe

I think I have now understood what you mean:

Usually, it is common to get something between 60-70% of theory when using n-butylamine as catalyst in Henry rxn with plain benzaldehyde and slight molar excess nitroethane (with toluene solvent and reflux temperature) - and since you got 51% and about 65% are common, you achieved 78.5% of the common yield one usually gets in reality; this is what you wanted to know, right?

icecool · Insistent Chemist

SWIM recrystalized the P2NP from IPA and when it was cold there was no liquid left under strong vacuum there was no IPA sucked out of the crystals so SWIM poured water over them to wash out the IPA and well they are drying now and they are only SLIGHTLY less yellow then they were before, swim guesses they were of quite good purity already.
And he did use a bit too much IPA so he evaporated off some and he hopes no P2NP evaporated during this since at a certain moment when he stirred the mixture there came a bit of foam on top op the boiling IPA.
anyway that is already something for the next time that is learnt now...

brain · Linguist Extraordinaire

hm, on large scale [2-3kg] recrystalization is to trouble... beter idea is :throw it to boiling water-the p2np will melt,, and go up ! some red oil will form on the bottom of baker, then let it coll, suck water an reddish oil,, let it coll Smile

its not the best way-but in that amounts-good, maybe no purest-but enough for amphetamine synthesis...

IndoleAmine · Dreamreader Deluxe

May be that on a 2-3 kg scale, recrystalization may need a bit much solvent Very Happy

- but hitting P2NP with hot water is somewhat a bad idea, it becomes less pure instead of becoming purer: because some of it will be destroyed and form benzyl alcohol and nitroethane, which will contaminate your P2NP.....

(better dissolve in toluene, wash with brine until washes stay clear (can be done in a large beaker, by siphoning off the brine after each wash), then dry the toluene, remove solvent by distillation under reduced pressure, and then cool the remaining oil to induce crystallization...)

i_a

brain · Linguist Extraordinaire

in my practice it was the best Wink

-hot water-it can be~60-70C... dont have to be 100C
-puryty fine for amph synth.!! Smile

IndoleAmine · Dreamreader Deluxe

I believe you that it is fine for phenylisopropylamine synthesis.. Wink

How was the color of the P2NP after crystalization? Red, or orange, maybe yellow, or even light yellow?

brain · Linguist Extraordinaire

orange-yellow p2np
-after recrystalization from toluene : light yellow (but hawe to get rid of the toluene !! when crystals ar big-it is problem)
-after puryfying [with hot wather] : yellow (not orange-yellow)