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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Jens on January 15, 2016, 06:32:59 AM

Title: Selective protecting of primary alcohol groups in beta-cyclodextrin
Post by: Jens on January 15, 2016, 06:32:59 AM

Hello everyone

I am a 3rd term student in chemical engineering (not really sure if this is the right place to post since I am only 3rd term)

I have a question about NMR analysis of the compound: heptakis(6-O-TBDMS)-β-Cyclodextrin
According to litterature it should be possible to have good yield on the product using anhydrous pyridine as solvent. My question is regarding how to ensure that the product obtained is indeed heptakis(6-O-TBDMS)-β-Cyclodextrin. Can this be done by proton NMR analysis?
I know that the integrals of the proton NMR peaks can be used to tell if there is only one TBDMS group pr glucopyranose unit. I am unsure however if the chemical shift of the protons on the 6th carbon will vary enough to tell if the TBDMS group is placed there.

I assume that the lower electronegativity of Si vs H will make the C-6 protons become less shielded and thus increase their chemical shift?

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Any help is appreciated

Best regards

Title: Re: Selective protecting of primary alcohol groups in beta-cyclodextrin
Post by: Jens on January 17, 2016, 05:50:42 AM

The protons on the C-6 carbon should shift their chemical shift values when the silicium atom is introduced to the molecule. I think that NMR analysis should be easily sensitive enough to register the difference.