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Author Topic: Synthesis : Glycols(diols) from Alkenes  (Read 5890 times)

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jmarjorie

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Synthesis : Glycols(diols) from Alkenes
« on: March 20, 2006, 12:51:12 AM »

Dear All,

I wish to attain a 'one-pot' synthesis of a diol from an alkene, and have drawn up a reaction scheme; pls let me know if the following is feasible:
Points to note :
1) The Alkene is an aliphatic hydrocarbon and is water soluble
    (soluble in Ethanol,the resultant mix is soluble in water)
2) The reaction temperature in both cases is 25 degrees C
3) There are no other functional groups present in the alkene

                              REACTION    SEQUENCE

   C = C         +           HOCl     ---------> C(OH)-C(Cl)
                      (5% NaOCl, pH 6.5)                    
                                                                   

   C(OH)-C(Cl) + 2M  NaOH (aq)  --------> C(OH)-C(OH)
   
 
Is the above scheme feasible and viable ?
If possible, what would be probable yields ?
Will the diol undergo any changes, eg dehydration on heating to 100 deg C
Any side reactions,considering that Ethanol is present with Hypochlorite ?

Thanks in advance,
Best regards,
jmarjorie
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AWK

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #1 on: March 20, 2006, 02:23:14 AM »

This scheme gives you good yield only for ethylene glycol synthesis, but as an intermediate you will obtaina   very dangerous ethylene oxide (oxirane) which is gaseous. Your product can contain also diethylene and triethylene glycols as side products..
« Last Edit: March 20, 2006, 02:24:21 AM by AWK »
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Albert

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #2 on: March 20, 2006, 02:25:37 AM »

This is the easiest way.
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fishyuyue

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #3 on: March 20, 2006, 02:30:10 AM »

I don't think it is feasible. HOCl is hypochlorous acid (HClO). For alkene, it undergoes electrophilic substitution. We can't get the Cl-C-C-OH, and get H-C-C-ClO(maybe)
The right method:the cold ,diluted and basic KMnO4 (aq) reacts with C=C to get diol
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B.W. McCann

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #4 on: March 20, 2006, 02:42:49 PM »

Would OsO4 be a good reagent to create a diol from an alkene in "one pot"?


Billy Wayne  





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fishyuyue

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #5 on: March 20, 2006, 07:37:12 PM »

Would OsO4 be a good reagent to create a diol from an alkene in "one pot"?


Billy Wayne  



OsO4 is very toxic chemical, not very safe.



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Pelle

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #6 on: March 21, 2006, 01:41:57 AM »

It's interesting how stuff like that isn't mentioned at all in Org. Chem. books. It just says something like "for synthesis of syn-diols use OsO4". Thanks for the info (not that I'd be digging up OsO4 to make diols any time soon, but good to know any way).

Can anyone tell me more about KMnO4 to make diols? Isn't there a risk of over-oxidation?
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tonyliruhan

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #7 on: March 21, 2006, 02:46:26 AM »

of course there is some risk of over oxidation. but by the strict control of the temperature and the pH of solvent, the yeild of diol will expectly higher
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Albert

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #8 on: March 21, 2006, 03:13:19 AM »

It's interesting how stuff like that isn't mentioned at all in Org. Chem. books. It just says something like "for synthesis of syn-diols use OsO4". Thanks for the info (not that I'd be digging up OsO4 to make diols any time soon, but good to know any way).

Have a look at this example.
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movies

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #9 on: March 21, 2006, 05:53:34 AM »

OsO4 is a far more efficient reagent for the production of 1,2-diols.  It is expensive and highly toxic, but it can be used safely in a laboratory setting.  Moreover, you can use it in catalytic amounts, sometimes less than 1 mol%.

KMnO4 has to be used stoichiometrically and over oxidation is a big problem.  It is used industrially to make 1,2-diols, however, because it is so cheap and relatively easy to use.
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Albert

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #10 on: March 21, 2006, 06:19:31 AM »

Quote
OsO4 is a far more efficient reagent for the production of 1,2-diols.

It's used in one of the final steps of the industrial synthesis of cortisone.
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HP

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Re:Synthesis : Glycols(diols) from Alkenes
« Reply #11 on: March 21, 2006, 08:18:21 AM »

Theres some new procedure for effective epoxidation alkenes exist. As i remember reagents from the type mixt fluoro-halogenes/acetonitrile/H2O2 used for epoxidation double bonds...I mean F2 gas + Br2 = FBr3 (i am not very sure :) which reagent in mixture with CH3CN and H2O2 makes the epoxy at mild conditions. I am not sure if there were and direct diolization procedure but its easy to convert epoxy compounds to the corresponding diols by hydrolyze them...
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