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Author: Subject: (tribromomethyl)benzene
ClF3
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[*] posted on 18-11-2018 at 20:43
(tribromomethyl)benzene


Hi there,

My second post and my first about an *imaginary* experiment I conducted this weekend I'm hoping you guys may confirm that I did the correct steps to achieve my product.

The resulting product I hope: (tribromomethyl)benzene.

The reaction steps were as follows: -
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6NaBr + 6HCl(aq) -----> 6NaCl + 6HBr

Then, 6HBr(aq) + 3H2O2 -----> 3Br2 + 6H2O

Then in a 1 dm3 Erlenmeyer flask the Bromine and water/brine mixture was heated and the Br2 run through a liebig condenser into a 1 dm3 round bottom flask connected to a 2 neck claisen adapter. The boiling flask contained 1 Mol of methylbenzene. The other neck of the claisen adapter was attached to a 300mm Graham condenser with a vigreux column attached on top.

When the Bromine had finished coming over from the Erlenmeyer flask through the liebig condenser, after it had finished dripping into the methylbenzene which was under strong stirring, the apparatus was quickly adjusted so the claisen adapter was removed and the Graham condenser was connected to the boiling flask containing the Br2 and C7H8. To the top of the Graham condenser the liebig condenser was attached and further to this the vigreux column was attached.

This setup was done as intense reflux was expected for several hours. Both the condensers had cold water running through them.

The boiling flask was set in a Mese heating mantle and the Br2 and C7H8 was put under reflux at 280°C under a 20W UV lamp with > 90% transmission at a frequency of 254nm. This was left under reflux and strong stirring for 7 hours then the heat switched off but stirring and UV light continuing.

-----
The product should be I'd have thought: -

Chemspider Link to Molecule

I read about the process at the excellent resource for UK A level syllabus here: -

Go to bottom of page for the reaction mechanism.

Anyway, tomorrow I will distill it, see what fractions come out saving each as I've feeling there's a mixture of mon, di and tri bromomethyl benzene.

As a side note - my UV lamp though I was only there 10 minutes as the reaction cooled when I turned the heating on the mantle off I have sun burn on my face and neck. I'll be wearing my welding mask and a scarf next time I enter the lab today around 5pm.

I'm finding it really hard to find information on this molecule does anyone know of a good resource I could read up on it? Perhaps then I could add to the Wiki on this site if I gather enough data.

Thanks for reading.





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Justin Blaise
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[*] posted on 23-11-2018 at 10:13


This might be useful to you.

https://www.journal.csj.jp/doi/abs/10.1246/cl.1984.1969

They purify the compounds via chromatography. I think you'll have a hard time distilling them without a strong vacuum source seeing as though BnBr already boils at 201 C.

Also, be aware that you're making some potent lachrymators in your reaction. BnBr is very unpleasant to work with even in a fume hood.
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[*] posted on 26-11-2018 at 11:06
I figured this the *very* hard way


Hi Justin,

I haven't read the link you posted yet but what you said about potent lachrymators... yes I can sincerely vouch for this.

Firstly the pressure in the speratory funnel was just to much and squirted out missing my eye by the edge of my goggles. Thank god for PPE, however the resulting spillage on my hand and face nearly immediately started burning and the fumes caused me to prolifically start crying and slobbering.

After a run upstairs and jump in the shower minding my never regions it calmed a little but my eyes were messed for days.

That stuff is nasty and I totally regret trying to make something I didn't understand. A lesson learned - literally a baptism of fire.

I'm now trying to find something that I can clean my glassware up with nicely. Without the tears...

Each time I go into my lab my eyes start burning...

God I feel like an idiot.

Thanks for the link, I'll check it now.




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[*] posted on 26-11-2018 at 11:30
Oh forgot to say


I used a (approx.) 440nm UV lamp. 10 minutes exposure and I also had sunburn which I felt the next evening.

Bad stuff.





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[*] posted on 26-11-2018 at 11:36


Feel a little better reading this:

http://blogs.sciencemag.org/pipeline/archives/2013/12/09/wha...




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