BIOC 3110 Lecture Notes - Lecture 10: Aldose, Alpha And Beta Carbon, Oligosaccharide
29 Sep 2016
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Chapter 10: carbohydrates: carbohydrate chemistry and isomers. Contain 2 or more oh groups, and have formula (ch2o)n- can have aldehyde (aldose) or ketone(ketose) Stereoisomers-atoms connected in same spot, just different 3d arrangement: enantiomers- one spot switched, has only one stereocenter; sides flipped: d glyceradehyde vs. L-glyceraldehyde: diastereomers-not mirror images; must have 3 or more carbons; multiple asymmetric carbons. Anomers-differ on new asymmetric carbon after ring is closed (oh up vs oh down) How do rings form: aldehyde + alcohol hemiacetal. Glucose open chain, bond formed between c of aldehyde and c of alcohol on the other end forms ring with ester in it. Can form with oh above ring (beta) or bellow ring (alpha) 1/3 alpha, 2/3 beta, and less than 1 percent open chain form. In chair form, in the beta configuration, all of the axial atoms are protons, and bigger molecules are in equatorial, so less steric hindrance: ketone + alcohol hemiketal.
