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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: a confused chiral girl on May 31, 2007, 01:40:02 AM

Title: carbohydrate reaction
Post by: a confused chiral girl on May 31, 2007, 01:40:02 AM

Hi everyone  ;D

I am having some problems determining the choice of this reaction. I have the reaction posted below, and there are also 4 choices. I am thinking that the cyclic group would attach to both the O on the anomeric carbon, as well as to the O on the highest stereogenic centre which determines D/L structure.

So I am thinking that there are no cyclic structures adding on to the given structure, but none of the choices fit with my reasoning...

Title: Re: carbohydrate reaction
Post by: a confused chiral girl on May 31, 2007, 01:40:28 AM

choice 1)

Title: Re: carbohydrate reaction
Post by: a confused chiral girl on May 31, 2007, 01:42:09 AM

choice 2

Title: Re: carbohydrate reaction
Post by: a confused chiral girl on May 31, 2007, 01:42:48 AM

choice 3

Title: Re: carbohydrate reaction
Post by: a confused chiral girl on May 31, 2007, 01:43:32 AM

choice 4

thank you everyone  :)

Title: Re: carbohydrate reaction
Post by: Custos on May 31, 2007, 01:54:45 AM

The correct answer is choice 2. In the absence of cyclohexanol the sugar can ring close to give the hemiacetal. If you add an alcohol plus acid to a hemiacetal you get an acetal. Look up hemiacetal and acetal in your text and you'll see what I mean.