11-06-04 22:15
No 540066
Well Swim just wanted to have some neat P2P
and he had the stuff at hand to do the Grignard
Benzyl-mg- Chlorid , Acetonitril Stuff.
Unfortunately he fergot to buy new Mg Turning (he used up all)
and he had only Powder at hand , but he started to work
couriously whats gonna happen when using Powder instead of
Turings . At the beginning it lokked pretty bad.
Because the reaktion didnt want to start ... added iodine ...heated ... no reaktion , but then swim thougt about his Mag.stirrer and placed the flask on it started stirring and voila the thing began to react really heavily !
When the reaktion was complete Swim made an
mixture of Acetonitril and Et2O .
Cooled Benz Mag Chlorid and added the before made mixture .
All of sudden an really ugly Stuff appeared on the bottom
A Pretty hard ( Salt ???) white with a tint of grey .
What the F*** swim thought and wondered what that could be
when the addition was complete he thought about disposing
all of the ""produkt"" but he wanted to know what happens
if he added Hcl . said , done the whole mess dissolved
und enourmous masses of Gas and building up 2 Layers ,
a yellow neon green Top layer and a white , foam bubblin
on the bottom !
Can anybody tell me what this mess could be ?
well since noone wanted to tell me , i had to search myselfe
and found sth really nice .... Poodles intructions / writeups and he said this solid was formed in his reaktion too!! well sounds good swir thought and read on ..
but he filtered this solid out and exposed it to water (well better than my tries ) to get P2P forming !
well the only thing i have to do now is to extract with a little bit of Et2o and evaporat it . to gin crude P2P.
Wow damn simple .....
(The Archetypical "Good Guy")
11-08-04 21:06
No 540467
Noone here at the-hive has ever documented satisfactory results using that method. Poodles results are generally thought to be a wee bit optimistic
The best credibly sounding results report max. 20% yield using Et2O as solvent, and 40% using benzene.The short chained alkylnitrile is simply not reactive enough towards the grignard reactant. With benzylnitrile and a methylhalide grignard the results are much better.
The white stuff that precipitates is the HCl salt of benzylmethylimine along with different byproducts. When exposed to acid, the imine will decompose into a ketone.
All in all i'd advise you to use another route, unless you want to dedicate your work to real science and figure out how to boost the yields here. When you allready have benzylchloride and master grignard reactions, i'd advice you to use the acetylacetonate route. It gives excellent yields, and is quite simple.
Rhodium> Wouldn't it be appropriate to insert a short warning into poodles p2p writeup, warning people that the presented results are a bit "unique"?
Kind regards
Bandil
Only one way leads to Valhalla - Running amok with TOTAL VIKING POWER
(Stranger)
11-08-04 22:14
No 540477
Well i extracted the P2P and i have to say that the yield
is not as bad as exspected ~ 24 ml P2P
And I used 63 ml Benzylchlorid and little more than 38 ml
Acetonitril .
But my P2P is really dark ! dark brown colored , with a really
lets call it unpleasant smell , ( little bit like some sort of plant but this must be an ugly one ...)
(The Archetypical "Good Guy")
11-08-04 22:27
No 540479
How did you extract it and verify that it is P2P?
In my experience with this method, you get something from the distillation, with a b.p. not too far for that of P2P (cant remember the exact b.p., lost the notes). It is however NOT p2p...
Regards
Bandil
Only one way leads to Valhalla - Running amok with TOTAL VIKING POWER
(Stranger)
11-08-04 23:34
No 540497
Well started with acidifation of this funny white salt
followed by 3 times extraction with 35 ml Et2O( NaCl has been added to mixture .)
to remove the yellow color from the bottom (water ) Layer
. Et2O extracts pooled together and washed with Water .
Water removed by Dropping funnel and heatng to 110 C.
Well ill make a sample with anilin acrylation and compare Products by chromatography. by the way ( wich solvent dont know the english word for it // Fließmittel // works best ?)
And i also looked at the pics by xicori (Meerwein acrylisation...) and his crude >Keton looks exactly like mine !! the only Problem is my Vakuumpump broke .
( u can still turn it on but it makes really unpleasant sounds like sth is scraping insinde ...)
Can i destill it without too much loss @ atmospheric pressure ?
(Hive Addict)
11-09-04 17:11
No 540660
The problem isn't excactly the reactivity of the nitrile. One major problem is the fact that the nitrile is acidic enough to protonate the Grignard reagent, turning your precious benzylmagnesium chloride to plain toluene. The deprotonated acetonitrile then goes on and forms different side reaction products. I have a reference to back this up somewhere. Of course one can argue that it is about reactivity because if the reaction with the nitrile was much faster than a proton transfer, this problem would not exist. But proton transfers are known to be very fast reactions.
I think that another problem is the addition of a second molecule of the Grignard reagent to the formed salt of the imine (iminate?), the reason why Grignard reagent should be added to an excess of the nitrile and not the other way around.
However, the reaction is proven to give P2P in literature several times, yields are the problem.
fear fear hate hate
(Hive Bee)
11-09-04 19:30
No 540678
If the problem is deprotonation of acetonitril, then the exact same reaction but instead of hydrolysis with acid, reduction with NaBH4 to amphetamine is consulted should not give an 80% yield1. Am I wrong in my reasoning? As the reduction step comes post-imin formation...
1 JACS 109, 3378-3387 (1987) Procedure adapted from the synthesis of #49 (../rhodium /amphet