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Author Topic: Question regarding reaction workup - Extracting  (Read 898 times)

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Prof.Zzz

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Question regarding reaction workup - Extracting
« on: June 07, 2018, 03:06:14 AM »

I am confused with this procedure. Here they are converting styrene to 2-phenylethanol

Did the through the first organic layer? or did they combined it with the three organic layers used to extract the aquos layer.
Can anyone explain this to me please

Thank you

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sjb

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Re: Question regarding reaction workup - Extracting
« Reply #1 on: June 07, 2018, 04:47:31 AM »

Can you post the full procedure? My gut feeling is that yes this is a combination of organic solvent from the reaction and then the additional portions from the extraction. In addition, consider typing it out to aid search functionality.
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wildfyr

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Re: Question regarding reaction workup - Extracting
« Reply #2 on: June 07, 2018, 05:16:42 AM »

They had an organic layer from the reaction (DCM? EtOAc?), then added water and the organic layer was put aside. The water layer was washed 3x with ether, then then the 3 ether washes and and original organic layer were combined and washed with water, brine, and dried with mag sulfate.
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Marjan

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Re: Question regarding reaction workup - Extracting
« Reply #3 on: June 07, 2018, 08:52:48 AM »

Are you doing this reaction, or are you just pondering it?

If you are doing this reaction, just TLC both extracts and see where your product is.
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crawlingmcedge

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Re: Question regarding reaction workup - Extracting
« Reply #4 on: June 07, 2018, 08:59:03 AM »

Wildfyr has it correct. The ether extraction is to get any soluble organic material that didn't come out with the first organic layer.

Not sure why they're washing the organic layer with water before the brine though. The point of the brine is to get water out, so adding water to that before a brine wash + mag sulphate wash is weird.
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wildfyr

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Re: Question regarding reaction workup - Extracting
« Reply #5 on: June 07, 2018, 09:07:14 AM »

I guess they are just making extra sure no water solubles are in the organic layer, since they did extract an aqueous layer 3x with ether. The they suck the water that got in there from that wash out with the brine and mag sulfate.

Probably unnecessary.
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Prof.Zzz

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Re: Question regarding reaction workup - Extracting
« Reply #6 on: June 13, 2018, 02:20:35 AM »

Thank you for your reply.

The ether extract seems immersible with the organic layer from the reaction. not sure why.

Here is the procedure:
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Prof.Zzz

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Re: Question regarding reaction workup - Extracting
« Reply #7 on: June 13, 2018, 02:27:54 AM »

Better quality;

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Doc Oc

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Re: Question regarding reaction workup - Extracting
« Reply #8 on: June 13, 2018, 05:26:33 AM »

Short answer: You combine all the organic layers before the final washes with water/brine.

Longer answer: After the oxidation step you separate the THF/aqueous layers. Extract the aqueous with ether, then add the THF to all of the ether extracts. Wash that whole thing with water and brine. Dry, rotovap, column.

I guess they are just making extra sure no water solubles are in the organic layer, since they did extract an aqueous layer 3x with ether. The they suck the water that got in there from that wash out with the brine and mag sulfate.

Probably unnecessary.

Definitely unnecessary, a pet peeve of mine. Sometimes people overdo on washes for no good reason, it's a waste.
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clarkstill

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Re: Question regarding reaction workup - Extracting
« Reply #9 on: June 13, 2018, 11:58:13 PM »

Definitely unnecessary, a pet peeve of mine. Sometimes people overdo on washes for no good reason, it's a waste.

I agree with this - often washes are entirely pointless. With THF there might be some justification however - I guess the aqueous layer is actually a THF/water mix, so there's a chance organics might be a little soluble in it. Just playing devil's advocate!
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