Organic Chemistry question!!!

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yalla22

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For Orgo lab buffs out there, I have my final exam tomorrow and have a few urgent questions about hydroborations:( I understand the mechanism but dont understand how the lab procedure fits into the mechanism...
For example, why do we add NaOH along with the hydrogen peroxide? Why is diethyl ether added? And what are we extracting from what during the last phase of the experiment?

Any help would be appreciated!!!!

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A hydroxide ion, in your NaOH, is generally always there to take a proton. I believe the hydrogen peroxide would be an oxidizing agent. Hard to tell without knowing what your starting product was and what you were supposed to end up with. Really hard to tell without reading the lab manual too. I just looked in mine..that reaction sounds similar..what is it entitled in your book?

Alicia
 
Basically you take 1-octene and convert it to 1-octanol...we add borane THF solution with 1-octene and stir for 45 minutes. then is says we have to add NaOH and hydrogen peroxide to the solution ( i understand why we add h2o2 but not the naoh)....then we have to stir for another hour, cool to room temp and then add diethyl ether to extract it..then it says to do another extraction with hcl (why??)
 
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The ether extracts the product and then gets boiled off. The HCl removes remaining OH. Two years removed from Organic Synthesis, that's the best I can do.
 
Et2O = solvent (easily removed at the end of the reaction)

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The intermediate of this reaction is B(OR)3

The B is HUGELY electro positive (or...non-electronegative). It likes being surrounded by e- donating oxygen atoms. We can think of BO3 as a good leaving group. OH- attacks the R and OB(OR)3 leaves. This happens two more times resulting in Na3BO3.

In otherwords, the OH is what actually forms the alcohol.

Because this is done in base the newly formed alcohol gets deprotonated (R-O-) and must be extracted using HCl (forming R-OH)

N/A
 
Whoops..I think Nevada is right. I'm wrong.
 
For Orgo lab buffs out there, I have my final exam tomorrow and have a few urgent questions about hydroborations:( I understand the mechanism but dont understand how the lab procedure fits into the mechanism...
For example, why do we add NaOH along with the hydrogen peroxide? Why is diethyl ether added? And what are we extracting from what during the last phase of the experiment?

Any help would be appreciated!!!!
http://www.organic-chemistry.org/namedreactions/brown-hydroboration.shtm

See the above webpage. Basically you need to understand the whole mechanism of the rxn to understand the NaOH. Adding H2O2 oxidizes the intermediate boron species (remember 3 alkenes per BH3) to boronic ethers then NaOH hydrolyzes that species and liberates boronic acid and the free alcohol(s). In the last stage of your experiment you are extracting the alcohol (ether soluble) from the boronic acid (water soluble).:luck:
 
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