Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: wseguins on October 07, 2013, 10:36:26 AM
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Hello, I'm trying the reaction of glycerol with tosylate, but according to the NMR results, the secondary hydroxyl not reacted with the tosylate. Also tested with propylene glycol to confirm the result was not equal to secondary hydroxyl reacted with the tosylate, only the primary reacts.
What do I do guys?? I was reading the literature and perhaps mesylato could be an option. What do you think?
The reaction that I'm using is as follows:
alcohol (10 mmol) was dissolved in chloroform (10ml) at 0 ° C, pyridine (20mmol) and tosylate (15mmol). After two and a half hours of stirring washed with ether and HCl and sodium bicarbonate.
Help me, please!!!
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Did you try propanole-2 to confirm. Probably is a steric problem to get 3 tosylates to the glycerol.
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Did you try propanole-2 to confirm. Probably is a steric problem to get 3 tosylates to the glycerol.
I did the reaction using iso, n, tert propanol. However, from what I observed had no reaction with the secondary hydroxyl. Already redid the calculations and the problem seems to be with the tosylate which does not react with the secondary hydroxyl.
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So if I understand correctly you want to tosylate all three OH groups?
Obviously the primary will react fastest. If the secondary OH reacts you may well end up with the epoxide tosylate.
Try adding some dimethyl-amino pyridine as a catalyst.
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So if I understand correctly you want to tosylate all three OH groups?
Obviously the primary will react fastest. If the secondary OH reacts you may well end up with the epoxide tosylate.
Try adding some dimethyl-amino pyridine as a catalyst.
Actually I want to do tosylate or mesylate propylene glycol. The idea of using glycerol is because it is inexpensive. But if you must use propylene glycol, it's okay.
To answer your question I want to react to one primary and one secondary hydroxyl.
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That will not be possible with glycerol.
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That will not be possible with glycerol.
It is true the reaction of glycerol with tosylato seems unfeasible, but will mesylate has the same behavior tosylato? Or is it possible to use mesylate secondary hydroxyl. I find nothing in the literature.
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Mesylate will be worse as it is a better leaving group than tosylate, so you will get a mess.
Perhaps you should acylate the primary OH, then make your tosylate on the secondary do your chemistry then remove the acyl groups. Or you could make the cyclic acetal with the two primaries.
We really need to know what you want to do after making the tosylates. Tell in general if you can't be specific.
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Mesylate will be worse as it is a better leaving group than tosylate, so you will get a mess.
Perhaps you should acylate the primary OH, then make your tosylate on the secondary do your chemistry then remove the acyl groups. Or you could make the cyclic acetal with the two primaries.
We really need to know what you want to do after making the tosylates. Tell in general if you can't be specific.
I want to react tosylate of propylene glycol with a diamine. I liked the suggestion acylate the primary OH. You have some protocol to get me through?
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Just use an acid chloride and triethylamine in a solvent.
Use a small excess of the alcohol.
Surely you have acylated alcohols before.
Have a look in organic synthesis.
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Just use an acid chloride and triethylamine in a solvent.
Use a small excess of the alcohol.
Surely you have acylated alcohols before.
Have a look in organic synthesis.
Thank you for the valuable tips.
Hug!