Organic Chemistry
9th Edition
ISBN: 9781305080485
Author: John E. McMurry
Publisher: Cengage Learning
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Chapter 25.SE, Problem 55AP
Interpretation Introduction
Interpretation:
To draw the pyranose form of α-D-galactopyranose, β-D-galactopyranose.
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D-Xylose in aqueous solution exists in the pyranose form as a mixture of α and β anomers. Furanose and acyclic forms are present in negligible amounts and can be ignored.
A sample of pure α-D-xylopyranose is dissolved in pure neutral water. The optical rotation is then measured immediately using a polarimeter. The specific rotation [??]?? is +93.6°.
The optical rotation is then observed to decrease with the passage of time, and the solution is allowed to reach equilibrium. Eventually the specific rotation stabilises at [??]?? = +18.8°. The anomeric ratio at equilibrium a : β is 37 : 63. A sample of pure β-D-xylopyranose is not available.
Using this information, predict the specific rotation of pure β-D-xylopyranose. Show how the a and β anomers equilibrate using a mechanism, assuming the presence of a trace amount of base as catalyst.
Ribose, a carbohydrate with the formula shown, forms a cyclic hemiacetal, which, in principle, could contain either a four-membered,
five-membered, or six-membered ring. To determine which ring is formed, ribose is treated with methanol in the presence of an acid
catalyst. The products are then isolated and treated with
NaIO, then with
H₂O*.
HO
OH
OH
OH
Ribose, C5H10O5
H
9.81
**
MeOH
H*
A & B
isomeric cyclic
acetals with
formula C6H12O5
Assuming that ribose formed a five-membered ring cyclic hemiacetal, draw the structure of the sodium periodate digestion
products.
▼
• Use the wedge/hash bond tools to indicate stereochemistry where it exists.
• Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner.
1. NalO4,
2. H₂O*
MeOH products
4
SIF
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Like glucose, galactose mutarotates when it dissolves in water. The specific rotation ofa-d-galactopyranose is +150.7°, and that of the b anomer is +52.8°. When either ofthe pure anomers dissolves in water, the specific rotation gradually changes to +80.2°.Determine the percentages of the two anomers present at equilibrium.
Chapter 25 Solutions
Organic Chemistry
Ch. 25.1 - Prob. 1PCh. 25.2 - Prob. 2PCh. 25.2 - Prob. 3PCh. 25.2 - Prob. 4PCh. 25.2 - Prob. 5PCh. 25.3 - Prob. 6PCh. 25.3 - Prob. 7PCh. 25.4 - Prob. 8PCh. 25.4 - Prob. 9PCh. 25.4 - Prob. 10P
Ch. 25.5 - Prob. 11PCh. 25.5 - Prob. 12PCh. 25.5 - Prob. 13PCh. 25.5 - Prob. 14PCh. 25.5 - Prob. 15PCh. 25.6 - Prob. 16PCh. 25.6 - Prob. 17PCh. 25.6 - Prob. 18PCh. 25.6 - Prob. 19PCh. 25.6 - Prob. 20PCh. 25.6 - Prob. 21PCh. 25.6 - Prob. 22PCh. 25.6 - Prob. 23PCh. 25.7 - Prob. 24PCh. 25.8 - Show the product you would obtain from the...Ch. 25.SE - Prob. 26VCCh. 25.SE - Prob. 27VCCh. 25.SE - Prob. 28VCCh. 25.SE - Prob. 29VCCh. 25.SE - Prob. 30MPCh. 25.SE - Prob. 31MPCh. 25.SE - Glucosamine, one of the eight essential...Ch. 25.SE - D-Glicose reacts with acetone in the presence of...Ch. 25.SE - Prob. 34MPCh. 25.SE - Prob. 35MPCh. 25.SE - Prob. 36APCh. 25.SE - Prob. 37APCh. 25.SE - Prob. 38APCh. 25.SE - Prob. 39APCh. 25.SE - Prob. 40APCh. 25.SE - Assign R or S configuration to each chirality...Ch. 25.SE - Prob. 42APCh. 25.SE - Prob. 43APCh. 25.SE - Prob. 44APCh. 25.SE - Prob. 45APCh. 25.SE - Prob. 46APCh. 25.SE - Prob. 47APCh. 25.SE - Prob. 48APCh. 25.SE - Prob. 49APCh. 25.SE - Prob. 50APCh. 25.SE - Prob. 51APCh. 25.SE - Prob. 52APCh. 25.SE - Prob. 53APCh. 25.SE - Prob. 54APCh. 25.SE - Prob. 55APCh. 25.SE - Prob. 56APCh. 25.SE - Prob. 57APCh. 25.SE - Prob. 58APCh. 25.SE - Prob. 59APCh. 25.SE - Prob. 60APCh. 25.SE - Prob. 61APCh. 25.SE - Prob. 62APCh. 25.SE - Prob. 63APCh. 25.SE - D-Mannose reacts with acetone to give a...Ch. 25.SE - Prob. 65APCh. 25.SE - Prob. 66APCh. 25.SE - Prob. 67APCh. 25.SE - Prob. 68APCh. 25.SE - Prob. 69APCh. 25.SE - Prob. 70APCh. 25.SE - Prob. 71AP
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- Ribose, a carbohydrate with the formula shown, forms a cyclic hemiacetal, which, in principle, could contain either a four- membered, five-membered, or six-membered ring. To determine which ring is formed, ribose is treated with methanol in the presence of an acid catalyst. The products are then isolated and treated with NaIO4 then with H3O+. OH HO OH OH Ribose, C5H10O5 H MeOH H* A & B isomeric cyclic acetals with formula C6H₁2O5 1. NalO4 2. H₂O* MeOH products Assuming that ribose formed a six-membered ring cyclic hemiacetal, draw the structure of the sodium periodate digestion products. • Use the wedge/hash bond tools to indicate stereochemistry where it exists. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner.arrow_forwardThe most stable conformation of the pyranose ring of most D-aldohexoses places the largest group, CH2OH, in the equatorial position. An exception to this is the aldohexose D-idose. Draw the two possible chair conformations of either the a or ß anomer of D-idose. Explain why the more stable conformation has the CH2OH group in the axial position.arrow_forwardCompound A is a D-aldopentose that can be oxidized to an optically inactive aldaric acid B. On Kiliani-Fischer chain extension, A is converted into C and D; C can be oxidized to an optically active aldaric acid E, but D is oxidized to an optically inactive aldaric acid F. What is the structure of compound F? • Use the wedge/hash bond tools to indicate stereochemistry where it exists. You do not have to explicitly draw H atoms. If a group is achiral, do not use wedged or hashed bonds on it. • Show stereochemistry in a meso compound. • Do not include lone pairs in your answer. They will not be considered in the grading.arrow_forward
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