11:115:301 Lecture Notes - Lecture 10: Anomer, Asymmetric Carbon, Glyceraldehyde
22 Sep 2019
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Document Summary
Monosaccharides: aldehydes or ketones with 2 or more hydroxyls. Larger ones = tetroses, pentoses, hexoses, heptoses. Isomers: have the same molecular formula but different structures. Constitutional isomers: differ in the order of attachment to atoms. Stereoisomers: atoms are connected in the same order but differ in spatial arrangement. Diastereomers: isomers that are not mirror images. Epimers: differ at one of several asymmetric carbon atoms. Anomers: isomers that differ at a new asymmetric carbon atom formed on ring closure. Dha is the only one without chiral carbon. The # of possible stereoisomers = 2^n. Sugars often form a ring with themselves cyclize. When a keto sugar cyclizes hemiketal. When the anomeric oh is further derivatized or and or" instead of oh and or. Hemiketals must tautomerize to an aldose to be oxidized. Can"t go back and forth between acetal and hemiacetal. Cyclization of glucose to form a six-membered pyranose ring.
