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32.4.24: Chapter 25

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    460336
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    Problem 25-1
    (a) Aldotetrose
    (b) Ketopentose
    (c) Ketohexose
    (d) Aldopentose
    Problem 25-2
    (a) S
    (b) R
    (c) S
    Problem 25-3 A, B, and C are the same.
    Problem 25-4 The central carbon is bonded to C H 3 on right, C H 2 O H on left, hydrogen on the top and chlorine on the bottom.
    Problem 25-5 Fischer projection of aldotetrose. It comprises four carbon where C 2 and C 3 have an R configuration. C H O is positioned on the top.
    Problem 25-6
    (a) L-Erythrose; 2S,3S
    (b) D-Xylose; 2R,3S,4R
    (c) D-Xylulose; 3S,4R
    Problem 25-7 The structure of L-arabinose which is an aldopentose containing five carbon atoms and including an aldehyde functional group.
    Problem 25-8
    (a) The Fischer projection of L-xylose.
    (b) The Fischer projection of L-galactose.
    (c) The Fischer projection of L-allose.
    Problem 25-9 16 D and 16 L aldoheptoses
    Problem 25-10 The Fischer projection of D-ribose which is a simple sugar with molecular formula C 5 H 10 O 5.
    Problem 25-11 A  furanose D-ribose is presented. The cyclization of ribose occurs via hemiacetal formation due to an attack on aldehyde by C 4 hydroxyl group to produce a furanose ring .
    Problem 25-12 Structures of alpha D-fructopyranose and alpha-D fructofuranose with 6-membered and 5-membered  ether rings, respectively. In both structures, the anomeric  O H group on C 2 is pointing down.
    Problem 25-13 Structures of beta D-galactopyranose and beta-D-mannopyranose.  The C 4 hydroxyl group of beta galactopyranose is equatorial and  C 2 hydroxyl group of beta mannopyranose is axial.
    Problem 25-14 Structure of beta-L-galactopyranose with an axial OH at C 4 and three equatorial  O H groups at C 1, C 2 and C 3.
    Problem 25-15 α-D-Allopyranose
    Problem 25-16 Beta-D-Ribofuranose  reacts with iodomethane in the presence of silver oxide to form beta-D-ribofuranose tetramethyl ether in which the hydrogens of the hydroxyl groups are replaced by C H 3 groups Beta-D-Ribofuranose reacts with acetic anhydride in pyridine to form beta-D-ribofuranose tetraacetate in which the hydrogens of the hydroxyl groups are replaced by acetate groups
    Problem 25-17 D-Galactitol has a plane of symmetry and is a meso compound, whereas D-glucitol is chiral.
    Problem 25-18 The −CHO end of L-gulose corresponds to the −CH2OH end of D-glucose after reduction.
    Problem 25-19 D-Allaric acid has a symmetry plane and is a meso compound, but D-glucaric acid is chiral.
    Problem 25-20 D-Allose and D-galactose yield meso aldaric acids; the other six D-hexoses yield optically active aldaric acids.
    Problem 25-21 D-Allose + D-altrose
    Problem 25-22 L-Xylose
    Problem 25-23 D-Xylose and D-lyxose
    Problem 25-24 Fischer projection of N-acetylmannosamine. The reaction of N-acetylmannosamine with pyruvate ion involving a base to form neuraminic acid. The reaction has multiple steps.
    Problem 25-25
    (a) The hemiacetal ring is reduced.
    (b) The hemiacetal ring is oxidized.
    (c) All hydroxyl groups are acetylated.

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