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/sci/ - Science & Math

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11508456

cant wait to do my first grignard reaction at home x) Anonymous Sat Mar 28 05:06:30 2020 No.11508456 [Reply] [Original]

im doing a home chemistry hobby ever since finished gen chem I and II and organic chem I and II

at first i did a lot of fischer esterifications and built up a collection of fragrant esters, but i have to redo the large esters like nonyl acetate b/c i realized you have to react the alcohol to completion (Dean stark technique) to avoid contamination with 1-nonanol.

well while i wait for a dean stark trap to come in the mail, i'm working on doing the grignard reaction at home. I just made some hydrobromic acid from sodium bromide pool tablets, so i can convert alcohols to alkyl bromides.

i think i'm gonna start by making isopropyl bromide from isopropyl alcohol. i just got diethyl ether and propionaldehyde, still waiting for magnesium turnings. then i can react grignard reagents with acetone and propionaldehyde to make a lot of cool alcohols and discover their scents for myself

When working with alkyl bromides, you have to do it outside and wear a respirator and gloves, because they might be carcinogenic.

>>	Anonymous Sat Mar 28 05:29:07 2020 No.11508487 >>11508456 Ah yes grignard reactions, orgo seems like a lifetime away. Big feels

>>	Anonymous Sat Mar 28 16:01:39 2020 No.11509993 >>11508456 Nice job OP, moving fast. Grignards can be a real pain to initiate, good luck though

>>

Anonymous Sat Mar 28 16:12:47 2020 No.11510019

>>11508456
I have experience making grignard reagents at the pilot and small scale, 5-50 kg.

If you can, get a hold of dibromoethane, and an IR lamp. Add all of the Mg turnings to the fask/reactor with your solvent ((really would recommend THF over Et2O for safety concerns), though it really depends on your separation process) and about 10 ml or so of dibromo-.

Perhaps I'm preaching to the choir, and so ill close with suggesting that a pressure equalization funnel be used with your alkylhalide.

Be safe, grignard rxns will run away faster than the chemist can remediate the situation.

t. process chemist

>>	Anonymous Sat Mar 28 23:22:40 2020 No.11511144 File: 25 KB, 1013x893, poopoopoo.png [View same] [iqdb] [saucenao] [google] >>11510019 Uh, why use dibromoethane? Can you do a reaction like in picture attached?

>>	Anonymous Sat Mar 28 23:23:43 2020 No.11511148 >>11511144 i mean that intermediate molecule with one MgBr wouldn't really happen b/c quenching the adduct would quench the grignard reagent, but you know what i mean.

>>	Anonymous Sat Mar 28 23:25:27 2020 No.11511151 >>11510019 one more question if u happen 2 be reading this. is a 200 mm hempel column packed with raschig rings a descent enough fractionating column, or should i buy one more 200 mm column and stack it on top?

>>

Anonymous Sat Mar 28 23:40:57 2020 No.11511188

>>11511144
>Uh, why use dibromoethane?
magnesium turnings passivate, and form chemically impenetrable shells. In order to break open that shell, initiators are added. Bromoethane, iodine crystals, mercury chloride, and/or rapid stirring are some common ways of penetrating through to the bare metal

>>	Anonymous Sun Mar 29 00:02:58 2020 No.11511241 >>11511188 Meth cooks deserved to be anally raped with no lube, over and over again, for making iodine a suspicious chemical.

>>	Anonymous Sun Mar 29 06:19:54 2020 No.11511836 Cool choice. Did that in my lab a few weeks ago. Make sure there’s no residual water in the glassware. That will mess things up. Also, Just don’t react bromotoluene and ethanal to make phenylacetone and react it with methylamine if you catch my drift.

>>

Anonymous Sun Mar 29 06:37:53 2020 No.11511856

>>11508456
Make sure that your glassware is dry, any water will kill the reaction. Your solvent will also need to be dry, THF and diethyl ether is usually dried other sodium metal using benzophenone as an indicator. You will not be able to do this at home. I have used DMF that was dried over mol sieves to protect an alcohol as its silyl ether. If this would work with ethers is out of my experience, but it will reduce the water content.

>>

Anonymous Sun Mar 29 08:08:13 2020 No.11511956

>>11511151
That sounds workable to me, a packed 200 mm column. A taller column is always preferable in my experience, however. I would start with the 200, wrapped in tin foil, with glass fibre insulation around that. use the head temp reading to judge what's coming over.

there's a lot going on in fractional distillation, a taller column needs strong boilup, which usually means higher heat flux into the system/reactor. flooding the top of a column is worse than dumping the bottom.

If you have the funds... a splitter head /w take-off timer ontop of a silvered, vacuum-jacked, packed column is peak process chemistry.

tl:dr-work with the cock ya got. improvise, adapt, and overcome

>>

Anonymous Sun Mar 29 08:21:34 2020 No.11511968

>>11511144
ya sure can. keep in mind this rxn will be dummy exothermic, and so without an initiator, good luck getting the process running smoothly and not boiling over.

Further pushing my point about solvent choice...THF is irritating on skin and harsh smelling. Et2O is HIGHLY flammable, 2.6x denser than air, and a narcotic.

what im getting at is the rxn may run so hot, the Et2O boils out past the condenser-leaving behind more concentrated alkylhalide among Mg turnings, further accelerating the rxn into runaway territory.

>>	Anonymous Sun Mar 29 13:30:01 2020 No.11512602 >>11511241 Or maybe blame the government that prohibits chemistry because they don't like it when people get high.

>>	Anonymous Sun Mar 29 14:02:25 2020 No.11512664 >>11508456 Are you the guy who's always posting about esters and their smells? I've always wanted to get into those types of home experiments as well since I used to love chemistry, but I went the math/cs route in college.

>>	Anonymous Sun Mar 29 14:11:48 2020 No.11512689 >>11512602 I blame both. But methheads in particular need to be cleansed with holy fire

>>	Anonymous Sun Mar 29 16:05:46 2020 No.11513027 File: 101 KB, 785x731, 8234761239487191.jpg [View same] [iqdb] [saucenao] [google] >>11512689 >"PEOPLE WHO USE THE BAD MOLECULES ARE BAD PEOPLE"

>>	Anonymous Sun Mar 29 18:41:10 2020 No.11513427 >>11512664 >Are you the guy who's always posting about esters and their smells? yes

>>	Anonymous Mon Mar 30 06:56:38 2020 No.11514819 >>11508456 Please be careful, anon, gringard reagents are extremely strong bases!

>>	Anonymous Mon Mar 30 18:22:39 2020 No.11516365 >>11508456 wholesome bread