11-02-01 15:52
No 232123
Hi bees, there seems to be yet another rxn sweeping the hive like wildfire, the electrochemical oxidation of propenylbenzenes. I know i've looked em over at different times, and the acetonitrile always struck me as a minor hurdle, but lacking any strong advocate, there always seemed to be friendlier rxns to pursue. Not looking so much for specific proceedures here just general pros, cons and comparisons.
So i wonder if we could simply debate the relative merits of this rxn vs other routes to the ketone.
Downsides as i see them are
1 - aquisition of CH3CN
2 - working with CH3CN. I see the HCN is a product of partial combustion of CH3CN. Actually everything about this solvent strikes me as loathsome, maybe its just the cyanide thing bugging me, is that a valid concern?
3 - nessecity of good ventilation (is a fume hood a must have)
4 - obivously some dedicated equipment is inolved as well
the upsides as i see them
1 - great yeilds
2 - simple work-up
3 - easy to recover solvent, with a column. It doesn't form an aezotope with H2O does it?
4 - no reflux equipment mess round with
5 - doesn't take 24 hours!!!!
feel free to disabuse me of any mistaken notions here or add to the list, guess what i really want is some comparrison shopping. Maybe debunk acetonitrile myths.
Also asides from using Li salts or dilute H2SO4 reflux iare there other methods of hydrolysis that would be applicable here?
thanx
"All those memories lost like rain..."
(Chief Bee)
11-02-01 16:17
No 232130
Acetonitrile is not that toxic. I place it beside DMF in toxicity. Iwould not be scared of working with it without a fume hood (as long as I wouldn't boil it into the air).
The main obstacle with the method would be making/buying the electrochemistry equipment in my opinion.
(Stoni's sexual toy)
11-02-01 16:27
No 232133
> Downsides as i see them are
> 1 - aquisition of CH3CN
Shouldn't be that much of a problem. Acetonitril isn't uncommon in the lab.
> 2 - working with CH3CN. I see the HCN is a product of
> partial combustion of CH3CN. Actually everything about
> this solvent strikes me as loathsome, maybe its just the
> cyanide thing bugging me, is that a valid concern?
No. Almost every nitrogen containing substance will form HCN when partially burned. Many of today's plastics and fabrics contain acryl nitril, and if that shit burns then you get REALLY high amounts of HCN. That's one of the reasons most people don't burn to death in fires, they suffocate from CO and HCN.
> 3 - nessecity of good ventilation (is a fume hood a must have)
No. It's certainly not worse than a pseudonitrosite stink! Work outside if you're a pussy. Or close your reaction vessel, with a hose leading outside.
> 4 - obivously some dedicated equipment is inolved as well
Naah. A power supply (old computer power supply, or battery charger will do for a few tests) and a platinum anode (ok, not cheap, buy small and react longer instead. It isn't that difficult to aquire, and a one-time investment.
> the upsides as i see them
> 1 - great yeilds
Yes.
> 2 - simple work-up
Yes.
> 3 - easy to recover solvent, with a column. It doesn't
> form an aezotope with H2O does it?
Oh yes it does. It forms azeotropes with almost all solvents. But I know a way of how to easily separate it from water without drying agents.
> 4 - no reflux equipment mess round with
Oh yes you need that! And you need a bit more of equipment.
> 5 - doesn't take 24 hours!!!!
It will. For decent reaction sizes you will need quite some time, unless you invest in good cooling and a big platinum anode.
(Chief Bee)
11-02-01 16:31
No 232134
> But I know a way of how to easily separate it from water without drying agents.
You write that, but not how to do it? You tease.
(Stoni's sexual toy)
11-02-01 16:33
No 232135
Yes I know, I'm a meanie.
(Hive Bee)
11-02-01 17:20
No 232150
Antibody2,
just to give you a good feeling Uemura confirms Rhod and Osmium assessment of MeCN. There isn't a 'real' toxicity problem when you use it properly. It doesn't stink, fume, evaporate, kill you immediately, it doesn't harm you more than MeOH when used with care. Uemura's one is just beside the MeOH bottle, both equipped with the famous skull sign. BTW: My provider has MeCN is 11! different qualities. One of the main uses of MeCN is for HPLC, or metall trace analysis. Just don't order the one for 'organic synthesis'!
Os: How do you get rid of the acetrope with water, details pleaseeeee. Does your method work for MeCN/MeOH acetrope as well? Are you jokeing?
Carpe Diem
(Old P2P Cook)
11-02-01 17:58
No 232166
Actually everything about this solvent strikes me as loathsome, maybe its just the cyanide thing bugging me,
Then don't call it methyl cyanide, call it acetonitrile.
Years ago, when I would occaisonally purchase benzyl cyanide, it amused me to discover that the government mandated shipping restrictions (and hence shipping cost) were much less for phenylacetonitrile than for benzyl cyanide. I can only presume that some government clerk decided that since benzyl cyanide contained cyanide in its name that it must be some really poisonous stuff. Once I discovered this I stopped buying benzyl cyanide and purchased phenylacetonitrile instead.
(Chief Bee)
11-02-01 18:15
No 232171
LOL! That kinda rhymes with the outrageus MSDS's that comes with distilled water - "In case of spill, wash with copious amount of water"...
(Distinctive Doe)
11-02-01 19:45
No 232196
Yea Acetonitrile is no big deal, just don't wash your hands to many times with it and don't drink it. It is actually almost like water(I use it all the time) except it gets metabolized to cyanide. Its not very volatile. The only bad thing is that its not cheap, expect it to bee about 3 times the price of other common lab solvents.
I do get it on my hands ect with no obvious side effects.
(I have heard of fingernail polish remover containing acetonitrile, but I have never seen it.)
Do Your Part To Win The War
(Stranger)
11-02-01 22:28
No 232241
I read that you can also use DMSO or DMF. Did anybee do this? I think I can't get my hand on any acetonitrile. Hmmmm.
(Hive Bee)
11-03-01 04:55
No 232434
Acetonitrile is no big hurdle. As the document says any solvent lacking an o-h bond will work as a substitute.
And rhodium:
Are glass jars, pencils, and wallworts that hard to find?
(Chief Bee)
11-03-01 05:35
No 232452
synth: I was thinking of a real commercial electrolysis cell, not a ghetto variety.
(Hive Bee)
11-03-01 07:57
No 232493
Ab2,
Also asides from using Li salts or dilute H2SO4 reflux iare there other methods of hydrolysis that would be applicable here?
thermal rearrangement from epoxide to the ketone, see Post 227831 (uemura: "Ketones from Propenylbenzenes via the di-bromides", Novel Discourse)
(Stoni's sexual toy)
11-03-01 10:44
No 232521
Ooooops!
Was wrong! No platinum anode, graphit will do. Nice.
(Commodore "Mole Bouncer")
11-03-01 21:47
No 232702
looks like we're good to go then
, thanx for the debunking. now i gotta get a head around these new units and learn the nomenclature."All those memories lost like rain..."
(Hive Bee)
12-14-01 09:22
No 247426
So how about the DMSO will it possibly work as a solvent.
VL_
(Hive Bee)
01-22-02 02:31
No 259186
http://www.biologie.uni-hamburg.de/b-onl
Just look at the structure of any solvent in question and if it lacks an o-h bond your good to go.
(Hive Addict)
01-22-02 07:11
No 259249
In ../rhodium /guest.p
(Mr. Spock)
01-22-02 10:36
No 259318
Acetone isn't considered aprotic. DMSO, DMF, acetonitrile are better examples.
Live long and Prosper.