Organic chemistry, 7e Brown Chapter 25

CHAPTER 25—CARBOHYDRATES MULTIPLE CHOICE 1. What is the relationship between D-erythrose and D-threose? a. constitutional isomers b. enantiomers c. diastereomers d. tautomers ANS: C 2. What is the relationship between D-threose and L-threose? a. constitutional isomers b. enantiomers c. diastereomers d. tautomers ANS: B 3. What is the relationship between D-ribose and D-xylose? a. constitutional isomers b. enantiomers c. diastereomers d. tautomers ANS: C 4. What is the relationship between D-arabinose and L-arabinose? a. constitutional isomers b. enantiomers c. diastereomers d. tautomers ANS: B 5. Which of the following structures represent the same carbohydrate? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. 1, 2 and 3 ANS: D 6. Which of the following structures represent the same carbohydrate? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. 1, 2 and 3 ANS: C 7. Which carbon in the following carbohydrate is the anomeric carbon? a. i b. ii c. iii d. iv ANS: A 8. Which carbon in the following carbohydrate is the anomeric carbon? a. i b. ii c. iii d. iv ANS: A 9. Which of the following has a D-configuration? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. only 1, 2 and 3 ANS: B 10. Which of the following has a D-configuration? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. only 1, 2 and 3 ANS: D 11. What are the R/S stereochemical designations of C2 and C3 of D-erythrose? a. 2R,3R b. 2R,3S c. 2S,3R d. 2S,3S ANS: A 12. What are the R/S stereochemical designations of C2 and C3 of L-threose? a. 2R,3R b. 2R,3S c. 2S,3R d. 2S,3S ANS: B 13. What is (are) the major organic product(s) obtained from the following reaction? a. only 1 b. only 2 c. only 2 and 3 d. 1, 2 and 3 ANS: C 14. What is the major organic product obtained from the following reaction? a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: A 15. What is the major organic product obtained from the following reaction? a. 1 b. 2 c. 3 d. 4 ANS: B 16. Which of the following represents a furanose? a. only 1 b. only 2 c. only 3 d. only 2 and 3 ANS: B 17. Which of the following represents a pyranose? a. only 1 b. only 2 c. only 3 d. only 1 and 2 ANS: A 18. Which of the following represent a ketose? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. 1, 2 and 3 ANS: D 19. Which of the following represent an aldose? a. only 1 and 2 b. only 1 and 3 c. only 2 and 3 d. 1, 2 and 3 ANS: B 20. Which of the following is a disaccharide? a. glucose b. fructose c. sucrose d. mannitol ANS: C 21. Which of the following is an alditol? a. glucose b. fructose c. glucaric acid d. mannitol ANS: D 22. Which of the following is vitamin C? a. D-glucose b. D-mannitol c. L-ascorbic acid d. L-sorbose ANS: C 23. Which of the following is not a polysaccharide? a. amylose b. amylopectin c. glycogen d. ribulose ANS: D TRUE/FALSE 1. A 1,4-a-linkage between two glucose units produces a disaccharide called maltose. ANS: T 2. Starch, cellulose, and surcrose are all classified as polysaccharides. ANS: T 3. The difference between the pyranose and furanose forms of a given aldohexose is the ring size. ANS: T 4. Consider the structure shown below. The Haworth projection formula for the pyranose form of b-D-galactose is given below. ANS: F 5. Reduction of an optically active aldopentose with NaBH4 gives an optically inactive alditol. The aldopentose could be: ANS: T 6. Oxidation of optically active D-erythrose with nitric acid produces optically inactive meso-tartaric acid (below). The structure of D-erythrose is shown below. ANS: F 7. A glycoside is formed upon reaction of glucopyranose with NaBH4. ANS: F 8. The following compound will react with Tollens' solution. ANS: F 9. The following structure shows the correct assignment of the R or S configuration to each chirality center in sorbose. ANS: T 10. The following are two different methods of representing the same structure. ANS: T 11. Consider the following Fisher projections. They all convert to the same tetrahedral representation as shown below.. ANS: T COMPLETION Consider the following structures. Answer the following questions by placing the appropriate number or indicated letter in the blank. 1. Structure ____ represents a ketohexose. ANS: 2 two 2. Structure ____ represents a aldopentose. ANS: 1 one 3. The structures that represent reducing sugars are: a. only the ketoses. b. only the aldoses. c. all of these structures. ANS: c 4. The number of hydroxyl groups in the pyranose form of glucose is _____. ANS: 6 six 5. The number of the anomeric carbon in the following structure is _____. ANS: 2 two C2 6. The formula for maltose is: The number of the acetal carbon is _____. ANS: 1’ 7. The following monosaccharide has ________ equatorial hydroxyl groups. ANS: 3 three From the sugars below, choose the one that best fits each description below. Place the letter of the sugar in the blank to the left of the description. There is only one correct answer for each question. 8. _____ is a D-sugar. ANS: d 9. _____ is a deoxy sugar. ANS: b 10. _____ is a sugar with three chirality centers. ANS: a 11. _____ is a sugar which yields a single alditol upon reduction. ANS: b 12. The name of the following Fischer projection including stereochemistry is _____________________. ANS: (2R,3S)-dibromobutane (2R,3S)-dibromobutane (2R,3S)-dibromobutane (2R,3S)-dibromobutane 13. The fundamental difference between the monosaccharide, disaccharide, and polysaccharide classifications of carbohydrates is the number of _________________present. ANS: monosaccharides monosaccharide units Refer to the equilibrium below to answer the following question(s). 14. The enantiomer of ribose is drawn is _______. (D or L) ANS: D 15. The anomer of ribose is drawn is _______. (alpha or beta) ANS: Beta b 16. The correct name for the cyclic structure is__________________________. ANS: b-D-ribofuranose beta-D-ribofuranose PROBLEM 1. Complete the structure on the right so that it represents the pyranose form of the carbohydrate shown on the left as a Fischer projection. Place the substituents carefully so that their position in axial or equatorial positions accurately reflects the stereochemistry of the carbohydrate. ANS: 2. Complete the structure on the right so that it represents the pyranose form of the carbohydrate shown on the left as a Fischer projection. Place the substituents carefully so that their position in axial or equatorial positions accurately reflects the stereochemistry of the carbohydrate. ANS: 3. What are the two major organic products obtained from the following reaction? What is the relationship between them? (What type of isomers are they?) ANS: The two methyl glycosides are diastereomers of one another 4. What is the major organic product obtained from the reaction of glucose with glucose oxidase? ANS: 5. What is the major organic product obtained from the following reduction of glucose? ANS: 6. What are the two major organic products obtained from treatment of an a-hydroxyketone with periodic acid in water? ANS: 7. What are the major organic products obtained from treatment of a 1,2,3-triol with periodic acid in water? ANS: 8. What are the major organic products obtained from treatment of a methyl glycoside with periodic acid in water? ANS: 9. The textile rayon is produced by treatment of cellulose with carbon disulfide in aqueous sodium hydroxide. What type of functional group is introduced on the cellulose under these conditions? ANS: a sodium xanthate salt 10. The textile cellulose acetate is produced by treatment of cellulose with acetic anhydride. What type of functional group is introduced on the cellulose under these conditions? ANS: an acetate ester BIAF 7e Test Bank 17