24 - CHAPTER 24 Carbohydrates Carbohydrate is the general...

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CHAPTER 24 Carbohydrates Carbohydrate is the general name for various sugars C (H O) C n (H 2 O) n Glucose Fructose Ribose
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Carbohydrate is the general name for various sugars = Aldehyde or Ketone that contains at least two hydroxyl groups. Aldose Ketose Aldose Glucose Fructose Ribose Carbohydrate is the general name for various sugars Based on chain length, sugars are called trioses (C3), tetroses (C4), pentoses (C5) and hexoses (C6). Aldohexose Ketohexose Aldopentose Glucose Fructose Ribose
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Simple sugars are monosaccharides (= aldehyde or ketone containing at least two hydroxy groups). Complex sugars are formed by the linkage of simple sugars through ether bridges. A disaccharide is derived from two monosaccharides by the formation of an ether (usually acetal) bridge by the formation of an ether (usually acetal) bridge. Trisaccharides , tetrasaccharides and eventually polysaccharides are formed through additional ether are formed through additional ether bridges. (Starch and cellulose are two important biological polysaccharides.)
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Fischer projections depict all-eclipsed conformations. Monosaccharides whose highest numbered stereocenter has the same absolute configuration as that of D-glyceraldehyde are labeled D. Those having the opposite absolute configuration are Those having the opposite absolute configuration are labeled L.
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Note that the D (or R) label does not necessarily imply (+) and L (or S) does not necessarily imply (-). D-glyceraldehyde is dextrorotatory. D-erythrose is levorotatory. Almost all naturally occurring sugars have the D absolute configuration.
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Important Concepts Si l b h d t Simple carbohydrates are sugars : poly-hydroxy aldehydes (aldoses) poly-hydroxy ketones (ketoses) Fischer Projection Stereochemistry: D isomer : highest numbered stereocente is R D isomer : highest numbered stereocenter is R L isomer : highest numbered stereocenter is S Epimers are sugars related by inversion at one stereocenter (Most naturally occurring sugars are D isomers)
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If either pure glucose anomer is placed in water, the initial value of the specific rotation slowly changes to a constant value of +52.7 o .
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This note was uploaded on 12/26/2008 for the course CHEM CHEM 140C taught by Professor Finn during the Spring '08 term at UCSD.

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24 - CHAPTER 24 Carbohydrates Carbohydrate is the general...

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