Hi everyone,
i'm trying to synthetise some anthracene dyes for chemioluminescence, but to do that i need phenylacetylene, has anyone tried to synthetise it?
I know about a few methods, but they're quite unaccesible for me, for example:
Eliminitation of styrene dibromide via NaNH2 in lq.NH3.
Elimination of beta/alpha bromostyrene via lq.KOH
Elimination of styrene dibromide via KOH in isopropanol in hig pressure autoclave. (found in patnent)
But i read on orgsyn. that the elimination could be done in alcoholic KOH, but i'm not sure that it could be done without autoclave, what do you think
of it, or do you know any other accesible methods? That one with beta bromstyrene would be accesible if b/a. bromostyrene could be synthetised
easilly.
Thanks for any suggestions.garage chemist - 26-11-2010 at 12:21
I've made this substance myself. The method of choice is elimination of styrene dibromide with KOH (100% excess, e.g. 4 mol KOH per mole
1-phenyl-1,2-dibromoethane) in triethylene glycol.
It's described in the Organikum.
I have used glycerine (99%) instead of triglycol with fair success, as triglycol is too difficult to obtain here.
Powerful heating and efficient stirring is the key to success. You must use the bunsen burner for heating, an oil bath is useless (in Organikum they
use a molten metal bath).
I can look up the reaction conditions if you can't find the procedure.smuv - 26-11-2010 at 12:41
Is this for work/research or as a hobby?
If the former, buy the phenyacetylene, for the small amounts needed for dye synthesis, it is cheaper to buy it than make it.
Thanks
chemx01 - 26-11-2010 at 13:00
Thank you very much garage chemist for the suggestion, if you'd be so kind and send me the procedure, that would be wonderfull, i'm not sure what the
Organikum is. Is it the German organic chemistry book or is it some website?
Thanks.
smuv- I'm doing as a hobby, so i'm not able to buy it for me it's too expensive.S.C. Wack - 26-11-2010 at 15:41
Elimination of beta/alpha bromostyrene via lq.KOH
That one with beta bromstyrene would be accesible if b/a. bromostyrene could be synthetised easilly.
Vogel.chemx01 - 27-11-2010 at 00:13
Yes i found the procedure here, but i think that's much more complicated to prepare it, because i would need cinnamic acid or anhydrous alcohol to
prepare 2-phenylethanol, and also the yield of phenylacetylene according to Vogel is not very high so it's not worth to do it in such complicated way.
If i'd have 2-phenylethanol i wouldn't mind, but i rather wait for the garage chemist's procedure from Organikum.
[Edited on 27-11-2010 by chemx01]garage chemist - 27-11-2010 at 04:56
I don't have a scanned procedure for this, and the Organikum is a german book in paper form.
So allow me to describe the reaction conditions as I remember them:
A 3-neck flask is equipped with a mechanical KPG stirrer (magnetic stirring cannot be used), electrical thermometer consisting of a thermocouple in a
glass tube sealed at one end (no mercury thermometer must be used), and a distillation setup with water-cooled condenser.
For every 0,1 mol styrene dibromide, 0,4 mol KOH (taking into account its water content- the effective molar weight of KOH is 66g/mol) are dissolved
in 100ml 99% glycerin by heating to 100°C and swirling.
Then the styrene dibromide is added.
The stirrer is cautiously started, and when all dibromide has melted, turned up to a speed that effects good mixing of the two insoluble phases but
does not splash around the reaction mixture.
The cooling water in the condenser is turned on, and while stirring, the flask is heated with the burner until the reaction kicks in (at 160-180°C, I
think), as seen by the vigorous boiling as the product distills off as fast as it is formed. A two-phase distillate collects in the receiver.
The temperature is slowly increased (to 200°C and higher) until the distillation of product has practically ceased (at 230°C, I think- but you don't
need to boil the glycerin).
To the distillate, water is added and the organic phase (it was the lower one, I think! Test and don't discard anything until the end!) separated. The
aqueous phase is extracted twice with ether. The pooled organic phases are dried over Na2SO4, the ether distilled off and the product purfied by
fractional distillation in vacuum using an efficient column (very important, there is a large amount of impurities with higher bp than phenylacetylene
in the crude product). It boiled at ca. 45°C in membrane pump vacuum.
S.C. Wack - 27-11-2010 at 06:11
I don't think you're going to find an easier route to beta-bromostyrene than Vogel.
Organikum is also a pdf.
Weygand also gives the preparation starting from styrene.
