Author Topic: P2P / Benzylchlorid / Mg powder , Acetonitril  (Read 1907 times)

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P2P / Benzylchlorid / Mg powder , Acetonitril
« on: November 06, 2004, 10:15:00 PM »
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 .....


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Noone here at the-hive has ever documented...
« Reply #1 on: November 08, 2004, 09:06:00 PM »
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