Author Topic: O Leminger's Phenethylamines - posted by Karel  (Read 3996 times)

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Mountain_Girl

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My experience
« Reply #20 on: January 22, 2003, 01:58:00 AM »
I've tried the Zn/HCl on 2,5-DMNS with and without HgCl2, with no success.
Didn't want to wait for lab grade Zn to be delivered so I used ground up battery casing instead. I suspect that this was my source of failure.
I plan to try with lab Zn next time.


Sunlight

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2CH
« Reply #21 on: January 22, 2003, 06:04:00 AM »
I've done several times the 2,5 DMNS rdxn, and it works always and really it is very simple. Better control temp around 10-15 C (russian patent say 25/30) and waht is really important is to keep the acid concentration >5 % of total wight of rxn. I've got only low yields when I bought a sep funnel and I confused the scale of the funnel, I added less acid during a important part of rxn ( a bit soned may be ?).  You'll get always a decent to good yield using 3-6 part of Zn to nitro, with the correct amount of acid.
It seems that doesn't matter solvent volume or temperature if it is <25-30, I've done it at -5 C and different volumes and yields were more or less the same, directly propotioned with the Zn amount. My tip is to work between 5-15 degrees, specially in the first stage, till the nitro dissappears, the  rxn is very exhothermic.

Sunlight

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Test done
« Reply #22 on: February 10, 2003, 03:44:00 PM »
I tried the Zn HCl reduction posted by Rhodium - Karel with 2,5 DMNS. I made slight changes to make the rxn more comfortable to me and correcting an excess of Zn over acid that was present in the first half of the original procedure, that is not necessary due not all the Zn reacts (like usually happens). Anyway these changes can't produce significative changes in the final result.

10 grams fo 2,5 DMNS were powdered in a coffee grinder, then 1 gram of the powder was put in a flask with 110 ml of denatured 96 % ethanol and 120 ml of 36 % HCl, and the suspension was cooled to 0 C in an ice salt bath. To the coffee grinder was added 25 grams of Zn powder and it was mixed together with the nitrostyrene in order to make an homogeneous mixture for the additions. The mixtured powder was added to the alcohol/aq.HCl solution in small portions in one hour, caring to prevent excesive fizzing, and the temperature was < 5 C. Then in half hour more were added 13 grams of Zn powder more, and the temperature was let to rise 10 C, and then it was let stirring 1 hour more with  temperature between 10-15 C. Finally, it was added 24 ml of HCl and 9 grams of Zn powder in one hour at about 15 C, and it was let stirring at room temperature for 16 hours.
The solution was filtered and the Zn was washed with 60 ml of water. The Zn was dried and it weighted 10.3 gr, more than a 20 % unreacted.
The filtrate was washed twice with 50 ml of toluene, then added with cooling to a solution of 206 gr of NaOH in 344 ml of water, what promoted the formation of an alcoholic layer and the aqueous hydroxide layer (almost all dissolved). It was transfered to a 1 liter separatory funnel and the alcoholic layer was separated, then the aqueous layer extracted twice with 60 ml of toluene and then with 40 ml of toluene. The extracts were washed twice with 60 ml water, then with brine and finaly with NaOH solution (to remove the rest of hydroxides), dried over 12 gr of KOH, filtered, then crystallized to afford 6.1 gram of off white 2CH HCl, 59 % yield.

It's a easy procedure, and yields are quite good. I've done similar tests and yield seem to depend more on the quantity of reacted Zn than other conditions such as solvent amount or even temperature. In this particular case, the initial concentration of acid is high, so the temperature was kept low (<5 C) but there was undesirable fizzing. The problem is the work up, it is not readily scalable for that reason, but this procedure is very elegant, and everything is done with a 1 liter separatory funnel. If you want more yield, you should add more Zn and more acid, then the work up will be bigger.

In my first tests I used a not very pure Zn, then I got a 54 % with a 5.5:1 Zn:nitro w/w, but then I bought a 97 % pure Zn, and yields were better. A 50 % + is always sure.