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Leah
#1 Posted : Monday, July 25, 2011 2:17:26 PM
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897. Shouldn`t the answer to this question be B?
899. I don`t really understand this question so if someone could explain that would be great!

Thanks!
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thivisharajagopal
#2 Posted : Thursday, July 28, 2011 5:13:27 PM
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Q897) When assigning alpha or beta, you are looking the CH2OH at C6 with reference to the OH at C1. For cellulose, if you look at the sugar on the left, the OH at C1 and CH2OH at C6 are CIS, therefore its beta linkage and you are correct.

Q899)The sugar itself contains a 5 carbons so its a FURANOSE and not PYRANOSE. So you are between option C or D. To determine if its ketose or aldehyde you have to identify the anomeric carbon. R group is OH and carbon it binds to is the hemiacetal. How do I know its hemiacetal? If I break the bond between the C-O in the ring you get primary alcohol (R=OH), alchol can only come from an aldehyde therefore its aldose and not ketose.

hope this helps!
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