Organic Chemistry,5th Edition L.G.Wade,Jr. Chapter 23 Carbohydrates and Nucleic Acids Jo Blackburn Richland College,Dallas,TX Dallas County Community College District ©2003，Prentice Hall
Chapter 23 Carbohydrates and Nucleic Acids Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
Carbohydrates Synthesized by plants using sunlight to convert CO2 and H2O to glucose and O2. Polymers include starch and cellulose. Starch is storage unit for solar energy. Most sugars have formula C(H2O)n, “hydrate of carbon.” => Chapter 23 2
Chapter 23 2 Carbohydrates • Synthesized by plants using sunlight to convert CO2 and H2O to glucose and O2 . • Polymers include starch and cellulose. • Starch is storage unit for solar energy. • Most sugars have formula Cn (H2O)n , “hydrate of carbon.” =>
Classification of Carbohydrates Monosaccharides or simple sugars >polyhydroxyaldehydes or aldoses >polyhydroxyketones or ketoses Disaccharides can be hydrolyzed to two monosaccharides. Polysaccharides hydrolyze to many monosaccharide units.E.g.,starch and cellulose have 1000 glucose units. => Chapter 23 3
Chapter 23 3 Classification of Carbohydrates • Monosaccharides or simple sugars ➢polyhydroxyaldehydes or aldoses ➢polyhydroxyketones or ketoses • Disaccharides can be hydrolyzed to two monosaccharides. • Polysaccharides hydrolyze to many monosaccharide units. E.g., starch and cellulose have > 1000 glucose units. =>
Monosaccharides Classified by: >aldose or ketose >number of carbons in chain >configuration of chiral carbon farthest from the carbonyl group CHO CH,OH 41 OH glucose,a C=0 D-aldohexose HO H HO H H OH H OH fructose,a H OH D-ketohexose H OH => CH2OH Chapter 23 CH2OH
Chapter 23 4 Monosaccharides • Classified by: ➢aldose or ketose ➢number of carbons in chain ➢configuration of chiral carbon farthest from the carbonyl group glucose, a D-aldohexose fructose, a D-ketohexose =>
D and L Sugars D sugars can be degraded to the dextrorotatory(+)form of glyceraldehyde. L sugars can be degraded to the levorotatory(-)form of glyceraldehyde. CHO C02↑ H一C一OH CHO C02↑ HO-C-H degrade HO一C-H degrade CHO CO2 H-C-OH H-C-OH H一C-OH CHO H一C一OH H一C一OH H一C- OH degrade H一C一OH CH2OH CH2OH CH,OH CH2OH D-(+)-glucose D-(-)-arabinose D-(-)-erythrose D-(+)-glyceraldehyde Chapter 23 5 =>
Chapter 23 5 D and L Sugars • D sugars can be degraded to the dextrorotatory (+) form of glyceraldehyde. • L sugars can be degraded to the levorotatory (-) form of glyceraldehyde. =>
The D Aldose Family CHO HOH CH OH D-(+)-glyceraldehyde CHO CHO H-OH HO十H H生OH H-OH CHOH CH,OH D-(-）erythrose D-(-)-threose CHO CHO CHO CHO H-OH HO- -H H-OH HO- 一H H-OH H- 一OH HO- 一H HO- -H H-OH H-OH H-OH H-OH CHOH CH,OH CHOH CH,OH ￥D-(-)-ribose D-(-)-arabinose D-(+)-xylose D-(-)-lyxose CHO CHO CHO CHO CHO CHO CHO CHO H-OH HO- 一H H- -OH HO- -H H -OH HO- 一H H -OH HO-H H-OH H- OH HO- 一H HO- -H H- 一OH H -OH HO- 一H HO-H H-OH H-OH H 一OH H- -OH HO- 一H H0一 一H HO- -H HO-H H-OH H-OH H-OH H-OH H-OH H-OH H-OH H-OH CH,OH CH,OH CH,OH CH,OH CH,OH CHOH CH,OH CHOH => D-(+)-allose D-(+)-altrose D-(+)-glucose D-(+)-mannose D-(-)-gulose D-(-)-idose D-(+)-galactose D-(+)-talose 6
Chapter 23 6 The D Aldose Family =>
Erythro and Threo Terms used for diastereomers with two adjacent chiral C's,without symmetric ends For symmetric molecules,use meso or d,/. CH2CH3 CH2CH3 COOH COOH H Br Br H H OH H OH H Br H Br H OH HO H CH3 CH3 COOH COOH erythro threo meso (d,l) 2,3-dibromopentane tartaric acid => Chapter 23 7
Chapter 23 7 Erythro and Threo • Terms used for diastereomers with two adjacent chiral C’s, without symmetric ends. • For symmetric molecules, use meso or d,l. =>
Epimers Sugars that differ only in their stereochemistry at a single carbon. 1CHO C2epimers CHO CHO H H-2 OH H-2 一 OH HO3H HO-3H C4 epimers HO3H H-4-OH H-4-OH HO牛H H-5-OH H-5-OH H CH,OH CH,OH CH,OH D-mannose D-glucose D-galactose => Chapter 23 8
Chapter 23 8 Epimers Sugars that differ only in their stereochemistry at a single carbon. =>
Cyclic Structure for Glucose Glucose cyclic hemiacetal formed by reaction of -CHO with -OH on C5. CHO H 一OH HO- -H CH,OH H CHOH 4 H OH H -OH CH-OH O H+ OH H OH H OH H +H+ H OH HO HO HO 2 CH2OH H OH OH OH Fischer projection on right side C6 rotated up Haworth projection H 6 H 6 CHOH CH,OH 5 HO 5■ HO OH 2 -H 3 OH T OH 分 H OH => chair conformation(all substituents equatorial) chair conformation(OH on CI axial) Chapter 23 D-glucopyranose 9
Chapter 23 9 Cyclic Structure for Glucose Glucose cyclic hemiacetal formed by reaction of -CHO with -OH on C5. => D-glucopyranose
Cyclic Structure for Fructose Cyclic hemiacetal formed by reaction of C=O at C2 with -OH at C5. ICH2OH 2C=0 H HO-CH2Q: 0-H 6 HO3-H OH 2 HO H4-OH 5K日 HO H4 3 H4 3 CH2OH H 一OH OH H OH H 6CH2OH D-fructofuranose D-fructose cyclic form => Chapter 23 10
Chapter 23 10 Cyclic Structure for Fructose Cyclic hemiacetal formed by reaction of C=O at C2 with -OH at C5. => D-fructofuranose