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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: luscofusco on February 17, 2023, 05:36:53 AM

Title: Alkene reactivity
Post by: luscofusco on February 17, 2023, 05:36:53 AM: I'm doing this exercise and it says provide reaction conditions. My idea is:

1. I can get OH on carbon 2 by a hydroboration oxidation
2. I can get OH on carbon 1 by oximercuriation demercuriation.

My question is: can I do both? If I do one I need an elimination to get the alkene again (this is just a guess, I'm not 100% sure) but isn't the H from the OH going to react faster than any of the other ones?

Since both OH are on the same plane, does epoxidation (for example with MCPBA) even work here? Because it would flip the configuration due to backside attack.
Title: Re: Alkene reactivity
Post by: Hunter2 on February 17, 2023, 01:40:30 PM: Use OsO4, or MnO4-,

https://www.chemistrysteps.com/wp-content/uploads/2019/06/syn-dihydroxylation-alkene-KMnO4-OsO4-mechanism.png

https://www.organische-chemie.ch/OC/Namen/upjohn3.GIF
Title: Re: Alkene reactivity
Post by: rolnor on February 19, 2023, 01:20:38 PM: Its a chiral product so you need to do asymetric dihydroxylation.

https://en.wikipedia.org/wiki/Sharpless_asymmetric_dihydroxylation#:~:text=Sharpless%20asymmetric%20dihydroxylation%20%28also%20called%20the%20Sharpless%20bishydroxylation%29,chiral%20quinine%20ligand%20to%20form%20a%20vicinal%20diol.
Title: Re: Alkene reactivity
Post by: Enthalpy on February 21, 2023, 06:17:33 PM: For my information: how toxic is OsO₄? I read astonishing data.
Title: Re: Alkene reactivity
Post by: Hunter2 on February 22, 2023, 05:43:31 AM: There are a lot of toxic compounds, lice arsenic, cyanide, phosgen, a.o. If to work with it , the corresponding safety rule and features have to be used
Title: Re: Alkene reactivity
Post by: sjb on February 24, 2023, 07:25:33 AM: Quote from: rolnor on February 19, 2023, 01:20:38 PM
Its a chiral product so you need to do asymetric dihydroxylation.

https://en.wikipedia.org/wiki/Sharpless_asymmetric_dihydroxylation

True - but it might just be referring to the Z diastereomeric pair.
Title: Re: Alkene reactivity
Post by: rolnor on February 24, 2023, 03:16:23 PM: As the structure of the compound is drawn, its chiral. It can be non-correctly drawn, yes. I think OsO4 will hydroxylate double-bonds in the body and be re-oxidized so even small amounts will hurt the biology inj the body. Compounds like phosghene will be consumed and will be neutralized in the body, its not catalytical. Many toxic things in nature are enzymes, Botuline and many snake-venoms are enzymes and they catalyticaly interfere with the biochemistry. I have worked a lot with OsO4 and its volatile, you get it in the rotavapor solvent waste, you get it everywhere. Not very nice.
Title: Re: Alkene reactivity
Post by: Babcock_Hall on February 27, 2023, 01:31:39 PM: There is a method that uses NMO (the N-oxidized form of N-methylmorpholine) as the oxidant, with OsO₄ as the catalyst. My inference is that using NMO is a safer alternative to using stoichiometric OsO₄.
Title: Re: Alkene reactivity
Post by: rolnor on March 13, 2023, 02:09:24 PM: OsO4 is expensive and toxic so deffinetly use it catalytic.