ºÝºÝߣ

ºÝºÝߣShare a Scribd company logo

Lecture8 carbohydrates

?
?
S
sanisaddam

This document discusses carbohydrate classification and structures. It notes that carbohydrates are composed of carbon, hydrogen, and oxygen and are a major energy source. There are three types: monosaccharides, disaccharides, and polysaccharides. Monosaccharides can be classified as aldoses or ketoses depending on whether they contain an aldehyde or ketone group. Many monosaccharides form cyclic structures with 5-6 carbons through a reaction between a hydroxyl group and aldehyde/ketone. Common monosaccharides like glucose and fructose form specific cyclic structures called Haworth structures depending on whether they are in the alpha or beta configuration.

1 of 29
Downloaded 78 times
Carbohydrates Classification Monosaccharides Chiral Carbon Atoms Structures of Important Monosaccharides Cyclic Structures 1
Carbohydrates ? Major source of energy from our diet ? Composed of the elements C, H and O ? Produced by photosynthesis in plants 2
Types of Carbohydrates ? Monosacchrides ? Disaccharides Contain 2 monosacchride units ? Polysacchrides Contain many monosacchride units 3
Monosacchrides ? Three Carbons = Triose ? Four Carbons = Tetrose ? Five Carbons = Pentose ? Six Carbons = Hexose 4
Monosacchrides ? Aldoses are monosacchrides with an aldehyde group and many hydroxyl (-OH) groups. ? Ketoses are monosacchrides with a ketone group and many hydroxyl (-OH) groups. 5
Learning Check C1 Identify each as tetrose, pentose or hexose, and as aldose or ketose H C O CH2OH H C OH C O H C OH HO C H H C OH H C OH H C OH CH2OH CH2OH A B 6
Solution C1 H C O CH2OH H C OH C O H C OH H C OH HO C H H C OH H C OH CH2OH CH2OH A B aldose, hexose ketose, pentose 7
Chiral Objects ? Chiral compounds have the same number of atoms arranged differently in space. ? A chiral carbon atom has four different groups attached 8
Mirror Images ? The three-dimensional structure of a chiral compound has a mirror image. ? Your hands are chiral. Try to superimpose your thumbs, palms, back of hands, and little fingers. Is it possible? Why or why not? 9
Tetrahedral carbon atom bonded to four different groups 10
ARE THERE CHIRAL C-ATOMS IN THESE MOLECULES? CH3CHClCH2CH3 A CH2ClCH3 B 11
Learning Check C2 Determine if there is a chiral carbon in each compound. Cl Cl H C CH 3 H C CH3 CH 2 CH 3 H A B 12
Solution C2 Cl Cl H C CH3 H C CH3 CH2CH3 H A Yes, 4 different B No, the groups are attached 2 H atoms to the second C atom are identical 13
14
Glyceraldehyde 15
D and L Notation ? D,L tells which of the two chiral isomers we are referring to. ? If the ¨COH group on the next to the bottom carbon atom points to the right , the isomer is a D-isomer; if it points left, the isomer is L. ? The D form is usually the isomer found in nature. 16
D notation O H C H C OH H C OH CH2OH Right = D 17
Glucose H C O H C OH HO C H H C OH H C OH CH2OH D-Glucose 18
Fructose CH2 OH C O HO C H H C OH H C OH CH2OH D-Fructose 19
Galactose H O C H C OH HO C H HO C H H C OH CH2OH D-galactose 20
Cyclic Structures ? Monosaccharides with 5-6 carbon atoms form cyclic structures ? The hydroxyl group on C-5 reacts with the aldehyde group or ketone group O o 21
Haworth Structure for D-Isomers The cyclic structure of a D-isomer has the final CH2OH group located above the ring. CH2OH o 22
Haworth Structure for D- Glucose ? Write ¨COH groups on the right (C2, C4) up ? Write ¨COH groups on the left (C3) down ? The new ¨COH on C1 has two possibilites: down for ¦Á anomer, up for ¦Â anomer 23
Cyclization of glucose 24
Haworth Structure for D- Glucose CH2OH CH2OH o o OH ¦Â OH OH OH OH OH ¦Á OH OH ¦Á-D-Glucose ¦Â-D-Glucose 25
d-fructose 26
Mutarotation ? Mutarotation: A small amount of open chain is in equilibrium with the cyclic forms. ? The most stable form of glucose is ¦Â-D- glucose . ¦Á-D-glucose D-glucose (open) ¦Â-D-glucose (36%) (trace) (64%) 27
Learning Check C3 Write the cyclic form of ¦Á-D-galactose H O C H C OH HO C H HO C H H C OH CH2OH 28
Solution C3 CH2OH OH o OH OH OH ¦Á-D-galactose 29

More Related Content

Lecture8 carbohydrates

  • 1. Carbohydrates Classification Monosaccharides Chiral Carbon Atoms Structures of Important Monosaccharides Cyclic Structures 1
  • 2. Carbohydrates ? Major source of energy from our diet ? Composed of the elements C, H and O ? Produced by photosynthesis in plants 2
  • 3. Types of Carbohydrates ? Monosacchrides ? Disaccharides Contain 2 monosacchride units ? Polysacchrides Contain many monosacchride units 3
  • 4. Monosacchrides ? Three Carbons = Triose ? Four Carbons = Tetrose ? Five Carbons = Pentose ? Six Carbons = Hexose 4
  • 5. Monosacchrides ? Aldoses are monosacchrides with an aldehyde group and many hydroxyl (-OH) groups. ? Ketoses are monosacchrides with a ketone group and many hydroxyl (-OH) groups. 5
  • 6. Learning Check C1 Identify each as tetrose, pentose or hexose, and as aldose or ketose H C O CH2OH H C OH C O H C OH HO C H H C OH H C OH H C OH CH2OH CH2OH A B 6
  • 7. Solution C1 H C O CH2OH H C OH C O H C OH H C OH HO C H H C OH H C OH CH2OH CH2OH A B aldose, hexose ketose, pentose 7
  • 8. Chiral Objects ? Chiral compounds have the same number of atoms arranged differently in space. ? A chiral carbon atom has four different groups attached 8
  • 9. Mirror Images ? The three-dimensional structure of a chiral compound has a mirror image. ? Your hands are chiral. Try to superimpose your thumbs, palms, back of hands, and little fingers. Is it possible? Why or why not? 9
  • 10. Tetrahedral carbon atom bonded to four different groups 10
  • 11. ARE THERE CHIRAL C-ATOMS IN THESE MOLECULES? CH3CHClCH2CH3 A CH2ClCH3 B 11
  • 12. Learning Check C2 Determine if there is a chiral carbon in each compound. Cl Cl H C CH 3 H C CH3 CH 2 CH 3 H A B 12
  • 13. Solution C2 Cl Cl H C CH3 H C CH3 CH2CH3 H A Yes, 4 different B No, the groups are attached 2 H atoms to the second C atom are identical 13
  • 14. 14
  • 16. D and L Notation ? D,L tells which of the two chiral isomers we are referring to. ? If the ¨COH group on the next to the bottom carbon atom points to the right , the isomer is a D-isomer; if it points left, the isomer is L. ? The D form is usually the isomer found in nature. 16
  • 17. D notation O H C H C OH H C OH CH2OH Right = D 17
  • 18. Glucose H C O H C OH HO C H H C OH H C OH CH2OH D-Glucose 18
  • 19. Fructose CH2 OH C O HO C H H C OH H C OH CH2OH D-Fructose 19
  • 20. Galactose H O C H C OH HO C H HO C H H C OH CH2OH D-galactose 20
  • 21. Cyclic Structures ? Monosaccharides with 5-6 carbon atoms form cyclic structures ? The hydroxyl group on C-5 reacts with the aldehyde group or ketone group O o 21
  • 22. Haworth Structure for D-Isomers The cyclic structure of a D-isomer has the final CH2OH group located above the ring. CH2OH o 22
  • 23. Haworth Structure for D- Glucose ? Write ¨COH groups on the right (C2, C4) up ? Write ¨COH groups on the left (C3) down ? The new ¨COH on C1 has two possibilites: down for ¦Á anomer, up for ¦Â anomer 23
  • 25. Haworth Structure for D- Glucose CH2OH CH2OH o o OH ¦Â OH OH OH OH OH ¦Á OH OH ¦Á-D-Glucose ¦Â-D-Glucose 25
  • 27. Mutarotation ? Mutarotation: A small amount of open chain is in equilibrium with the cyclic forms. ? The most stable form of glucose is ¦Â-D- glucose . ¦Á-D-glucose D-glucose (open) ¦Â-D-glucose (36%) (trace) (64%) 27
  • 28. Learning Check C3 Write the cyclic form of ¦Á-D-galactose H O C H C OH HO C H HO C H H C OH CH2OH 28
  • 29. Solution C3 CH2OH OH o OH OH OH ¦Á-D-galactose 29