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Carbohydrates
     Classification
   Monosaccharides
 Chiral Carbon Atoms
Structures of Important
    Monosaccharides
   C...
Carbohydrates

• Major source of energy from our diet

• Composed of the elements C, H and
 O

• Produced by photosynthesi...
Types of Carbohydrates
• Monosacchrides

• Disaccharides
     Contain 2 monosacchride units

• Polysacchrides
    Contain ...
Monosacchrides
• Three Carbons =   Triose

• Four Carbons =    Tetrose

• Five Carbons =    Pentose

• Six Carbons =     H...
Monosacchrides
• Aldoses are monosacchrides with an
  aldehyde group and many hydroxyl (-OH)
  groups.

• Ketoses are mono...
Learning Check C1
Identify each as tetrose, pentose or
hexose, and as aldose or ketose
  H
      C O                     C...
Solution C1
    H
        C O
                         CH2OH
    H C OH
                         C O
    H C OH
    H C OH...
Chiral Objects
• Chiral compounds have the same number
  of atoms arranged differently in space.
• A chiral carbon atom ha...
Mirror Images
• The three-dimensional structure of a chiral
  compound has a mirror image.
• Your hands are chiral. Try to...
Tetrahedral
carbon atom
bonded to four
different groups




                   10
ARE THERE CHIRAL C-ATOMS
  IN THESE MOLECULES?
      CH3CHClCH2CH3
           A

        CH2ClCH3
           B

          ...
Learning Check C2
Determine if there is a chiral carbon in
each compound.
     Cl                        Cl
H       C CH 3...
Solution C2
       Cl                       Cl
H      C CH3               H    C CH3
       CH2CH3                   H
A Y...
14
Glyceraldehyde




                 15
D and L Notation
• D,L tells which of the two chiral isomers
  we are referring to.
• If the –OH group on the next to the ...
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
  wi...
Haworth Structure for D-Isomers
The cyclic structure of a D-isomer has
the final CH2OH group located above the
ring.
     ...
Haworth Structure for D-
           Glucose
• Write –OH groups on the right (C2,
  C4) up
• Write –OH groups on the left (...
Cyclization of glucose




                         24
Haworth Structure for D-
            Glucose
     CH2OH               CH2OH
          o                   o    OH   β
    ...
d-fructose




             26
Mutarotation
• Mutarotation: A small amount of open
  chain is in equilibrium with the cyclic
  forms.
• The most stable f...
Learning Check C3
Write the cyclic form of α-D-galactose
               H       O
                   C
              H C O...
Solution C3

     CH2OH

OH        o
     OH
               OH

          OH
α-D-galactose
                    29
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Lecture8 carbohydrates

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Lecture8 carbohydrates

  1. 1. Carbohydrates Classification Monosaccharides Chiral Carbon Atoms Structures of Important Monosaccharides Cyclic Structures 1
  2. 2. Carbohydrates • Major source of energy from our diet • Composed of the elements C, H and O • Produced by photosynthesis in plants 2
  3. 3. Types of Carbohydrates • Monosacchrides • Disaccharides Contain 2 monosacchride units • Polysacchrides Contain many monosacchride units 3
  4. 4. Monosacchrides • Three Carbons = Triose • Four Carbons = Tetrose • Five Carbons = Pentose • Six Carbons = Hexose 4
  5. 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. 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. 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. 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. 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. 10. Tetrahedral carbon atom bonded to four different groups 10
  11. 11. ARE THERE CHIRAL C-ATOMS IN THESE MOLECULES? CH3CHClCH2CH3 A CH2ClCH3 B 11
  12. 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. 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. 14
  15. 15. Glyceraldehyde 15
  16. 16. D and L Notation • D,L tells which of the two chiral isomers we are referring to. • If the –OH 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. 17. D notation O H C H C OH H C OH CH2OH Right = D 17
  18. 18. Glucose H C O H C OH HO C H H C OH H C OH CH2OH D-Glucose 18
  19. 19. Fructose CH2 OH C O HO C H H C OH H C OH CH2OH D-Fructose 19
  20. 20. Galactose H O C H C OH HO C H HO C H H C OH CH2OH D-galactose 20
  21. 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. 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. 23. Haworth Structure for D- Glucose • Write –OH groups on the right (C2, C4) up • Write –OH groups on the left (C3) down • The new –OH on C1 has two possibilites: down for α anomer, up for β anomer 23
  24. 24. Cyclization of glucose 24
  25. 25. Haworth Structure for D- Glucose CH2OH CH2OH o o OH β OH OH OH OH OH α OH OH α-D-Glucose β-D-Glucose 25
  26. 26. d-fructose 26
  27. 27. Mutarotation • Mutarotation: A small amount of open chain is in equilibrium with the cyclic forms. • The most stable form of glucose is β-D- glucose . α-D-glucose D-glucose (open) β-D-glucose (36%) (trace) (64%) 27
  28. 28. Learning Check C3 Write the cyclic form of α-D-galactose H O C H C OH HO C H HO C H H C OH CH2OH 28
  29. 29. Solution C3 CH2OH OH o OH OH OH α-D-galactose 29

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