D /L carbohydrates..ring opening?

[fluoropHore]

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How can you tell if a carb is D or L?
Also, is there an easier way to "more easily" visualize opening carb rings to see the fisher projection?

 

[pfaction]

D: The CH2OH to the left of the oxygen in the ring will be pointing UP.
L: " pointing DOWN.

 

[fluoropHore]

can you elaborate- what about if its in a fisher projection? the CH2o2 will be usually in the vertical axis.

 

[chiddler]

in fischer projection, L is when the stereogenic carbon furthest away from the anomeric carbon is to the left.

ie

L is when carbon #5's OH is to the left. D is when carbon #5's OH is to the right.

The easiest way to imprint this in your mind is just to go check out examples. Go look up D and L fructose and look for differences. And other sugars.

 

[syoung]

use your right hand, make a fist and turn it to the left. the index fingers are the OH's on the vertical, the thumb is the anomeric carbon. Glucose is c2(OH r), c3(OH l), c4(OH r), c5(OH r), and ignore c6. call it f*** D glucose.