Chapter 7 Practice Problems PDF

CHAPTER 7 Practice Problems PART 1 1. Consider the three structures. (a) Which of these structures has the most angle strain? (b) Which of these structures has the most steric strain? (c) Which of these structures has the most torsional (eclipsing) strain? 2. Consider the images. For cis-1,3-d...

CHAPTER 7 Practice Problems PART 1 1. Consider the three structures. (a) Which of these structures has the most angle strain? (b) Which of these structures has the most steric strain? (c) Which of these structures has the most torsional (eclipsing) strain? 2. Consider the images. For cis-1,3-dimethylcyclohexane, which two chair conformations are in equilibrium? A B C D E F 1 3. Consider the molecule. Which of the answer choices contains a molecule that is the conformational diastereomer to the given molecule? 4. Given the planar trisubstituted cyclohexane, fill in the missing substituents (with H, Cl or Br) to complete the two possible cyclohexane chair conformations. Then, determine the more stable conformer. You might find it helpful to make a model of the cyclohexane to help visualize the chair conformations. Which is the more stable conformer? 2 5. Indicate the relationship between the two structures in the pair. Are they chair conformations of the same molecule? If so, are they conformational diastereomers, conformational enantiomers, or identical? If they are not conformations of the same molecule, what is their stereochemical relationship? What is the relationship? A. They are chair conformations of the same molecule, and they are conformational diastereomers. B. They are chair conformations of the same molecule, and they are conformational enantiomers. C. They are identical conformations of the same molecule. D. They are different molecules, and they are diastereomers. E. They are different molecules, and they are enantiomers. 3 6. State whether you would expect each of the following properties to be identical or different for the following two stereoisomers of 1,3-cyclohexanediol, and explain your reasoning. Two cyclohexane molecules are shown. The left-hand molecule has a solid wedge bond to O H from its top vertex and a hashed wedge bond to O H from its lower right vertex. The right-hand molecule has a hashed wedge bond to O H from its top vertex and a solid wedge bond to O H from its lower right vertex. a. Boiling point b. Optical rotation c. Solubility in hexane d. Density e. Solubility in (S)-3-methylhexane f. Dipole moment g. Taste (Hint: Your taste buds are chiral.) 7. Draw the two chair conformations of the sugar α-(+)-glucopyranose, which is one form of the sugar glucose. Which of these two conformations is the major one at equilibrium? Explain. 4 8. Name the compounds. PART 2 9. Predict the major organic product of the reaction: Add wedge-and-dash bonds to indicate stereochemistry. 5 10. The alkene shown undergoes bromination. (a) Draw the product(s) of bromination of this compound, including all expected stereoisomers (if any). Use wedge-and-dash bonds to designate the stereochemistry at any chirality centers, and make sure to draw an explicit hydrogen if a chirality center has one. (b) Characterize the starting alkene as having the E or Z configuration. (c) characterize the product(s). 11. Show the mechanism for the given reaction conducted at −5°C in CCl4. Cyclohexene + bromine ⟶ dibromocyclohexanecyclohexene Draw wedge and dash bond stereochemical structures, including H atoms at each chirality center, and include charges, electrons, and curved arrows. Details count. Draw one enantiomer only for any racemates. 6 12. Alkenes can be converted to alcohols by hydroboration-oxidation. (a) Draw the structure of the alcohol or alcohols formed in the reaction sequence. Clearly indicate stereochemistry by drawing a wedged bond, a dashed bond and two in-plane bonds per each chiral carbon. Draw hydrogen atoms that are connected to wedge-and-dash bonds. (b)Characterize the product or products of the reactions. 13. (a) Give the structures of all products including stereoisomers. (b) If more than one product is formed, give the stereochemical relationship, if any, of each pair of products, and their physical properties. 7 8