Chapter07

Chapter07 - BCH 4053 Spring 2001 Chapter 7 Lecture Notes...

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Chapter 7, page 1 BCH 4053 Spring 2001 Chapter 7 Lecture Notes Slide 1 Chapter 7 Carbohydrates Slide 2 Carbohydrates: Nomenclature • Hydrates of carbon • General formula (CH 2 O) n (simple sugars) or C x (H 2 0) y • Monosaccharides (simple sugars) • Aldoses and ketoses • Sugar derivatives • Sugar acids, sugar alcohols, deoxy sugars, sugar esters, amino sugars, glycosides • Oligosaccharides • Polysaccharides Slide 3 Monosaccharides • Carbon chain, 1 oxygen for each carbon • One oxygen is carbonyl, rest are alcohols • Aldose—carbonyl on carbon-1 (aldehyde) • Ketose—carbonyl on carbon-2 (ketone) • Number of carbon atoms can vary • Triose, tetrose, pentose, hexose, heptose
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Chapter 7, page 2 Slide 4 Monosaccharides, stereochemistry • Chiral carbons • n-2 for aldoses (trioses have one, tetroses two, etc) • n-3 for ketoses (tetroses have one, pentoses two, etc) • Fischer projection • D correlates with d-glyceraldehyde • L correlates with l-glyceraldehyde • See Figure 7.1 Slide 5 Stereochemistry, con’t. • Number of isomers = 2 n • where n = number of chiral centers 3 8 4 16 Hexoses 2 4 3 8 Pentoses 1 2 2 4 Tetroses 0 1 1 2 Trioses Ketoses n isomers Aldoses n isomers Slide 6 Monosaccharide, nomenclature • Sugar class refers to the penultimate (n-1) carbon configuration • D sugar if n-1 position has D configuration • L sugar if n-1 position has L configuration • Isomers at other positions distinguished by different names • See Figure 7.2 for aldoses, 7.3 for ketoses
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Chapter 7, page 3 Slide 7 Monosaccharide, nomenclature, con’t. • Learn the following structures: • Trioses: all • Tetroses: all • Pentoses: ribose, ribulose, xylulose • Hexoses: glucose, mannose, galactose, fructose Slide 8 Some stereochemical terms • Enantiomers, mirror image isomers • Configuration at every chiral carbon is different • See Figure 7.4 • Diastereomers, isomers with one or more configuration differences that are not enantiomers • Epimers, isomers that differ only at one chiral center Slide 9 Acetals and Ketals • Aldehydes can react with alcohols to form hemiacetals and acetals • Ketones can react with alcohols to form hemiketals and ketals R CH O R' OH R CH OH O R O O H + hemiacetal acetal H + R C O O R R C OH O R R' OH R C O R" " " hemiketal ketal + + The aldehyde and hemiacetal are in equilibrium, and depend on the concentration of the alcohol. Heating with acid and excess alcohol can cause dehydration between the alcohol and the hemiacetal to occur to form an
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This note was uploaded on 11/27/2011 for the course CHM 365 taught by Professor Thomaszamis during the Spring '06 term at FSU.

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Chapter07 - BCH 4053 Spring 2001 Chapter 7 Lecture Notes...

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