CHAPTER 20—DIENES, CONJUGATED SYSTEMS, AND PERICYCLIC REACTIONS

CHAPTER 20—DIENES, CONJUGATED SYSTEMS, AND PERICYCLIC REACTIONS MULTIPLE CHOICE 1. Which of the following are conjugated dienes? a. only 1 b. only 2 c. only 1 and 2 d. 1, 2 and 3 ANS: C 2. Which of the following are conjugated dienes? a. only 1 b. only 2 c. only 1 and 2 d. 1, 2 and 3 ANS: B 3. What is the IUPAC name of the following compound? a. 2,3-dimethyl-2,4-pentadiene b. (Z)-2,3-dimethyl-2,4-pentadiene c. 3,4-dimethyl-1,3-pentadiene d. (Z)-3,4-dimethyl-1,3-pentadiene ANS: C BIAF 7e Test Bank4. What is the IUPAC name of the following compound? a. (R)-3-vinyl-1-butene b. 3-methyl-1,5-pentadiene c. 3-methyl-1,4-pentadiene d. (R)-3-methyl-1,4-pentadiene ANS: C 5. What is the systematic IUPAC name of the following compound? a. (3S,4E)-3-ethyl-3,4-dimethyl-1,4-hexadiene b. (3R,4E)-3-ethyl-3,4-dimethyl-1,4-hexadiene c. (3S,4Z)-3-ethyl-3,4-dimethyl-1,4-hexadiene d. (3R,4Z)-3-ethyl-3,4-dimethyl-1,4-hexadiene ANS: A 6. Which of the following alkenes undergoes the least exothermic hydrogenation upon treatment with H2/Pd a. 1 b. 2 c. 3 d. 4 ANS: C 7. What is the correct order of exothermicity for hydrogenation of the following hexadienes upon treatment with H2/Pd (more exothermic less exothermic)? BIAF 7e Test Banka. 1 2 3 b. 3 1 2 c. 2 1 3 d. 3 2 1 ANS: B 8. Which of the following arrangements of p atomic orbitals gives the lowest energy -bonding molecular orbital of 1,3-butadiene? a. 1 b. 2 c. 3 d. 4 ANS: B 9. Which of the following arrangements of p atomic orbitals gives the highest energy -antibonding molecular orbital of 1,3-butadiene? a. 1 b. 2 c. 3 d. 4 ANS: C 10. Which of the following arrangements of p atomic orbitals of 1,3-butadiene has the greatest number of nodes? a. 1 b. 2 c. 3 d. 4 ANS: C BIAF 7e Test Bank11. What is the reactive intermediate in the reaction of 1,3-butadiene with HBr resulting in 1,2-addition? a. cyclic bromonium cation b. allylic cation c. allylic radical d. dienophile ANS: B 12. Which of the following terms describes the mechanism for the addition of Br2 to butadiene? a. electrophilic addition b. nucleophilic addition c. pericyclic addition d. conjugate addition ANS: A 13. What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 1 and 3 c. only 2 and 4 d. only 1 and 4 ANS: D 14. What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 1 and 2 c. only 1 and 3 d. only 2 and 4 BIAF 7e Test BankANS: B 15. Which of the following is(are) formed upon addition of 1 mol of Br2 to 1,3-cyclohexane? a. only 2 b. only 1 and 3 c. only 2 and 4 d. 1, 2 and 3 ANS: C 16. Which of the following is not a major organic product obtained from the addition of 1 mole of bromine to (E)-1,3-pentadiene? a. (E)-4,5-dibromo-2-pentene b. 3,4-dibromo-1-pentene c. (E)-1,4-dibromo-2-pentene d. (E)-1,2-dibromo-2-pentene ANS: D 17. What is the thermodynamic product obtained from the addition of 1 mole of bromine to 1,3-butadiene? a. 3,4-dibromo-1-butene b. (E)-1,4-dibromo-2-butene c. (Z)-1,4-dibromo-2-butene d. (Z)-2,3-dibromo-2-butene ANS: B 18. What is the kinetic product obtained from the addition of 1 mole of bromine to 1,3-butadiene? a. 3,4-dibromo-1-butene b. (E)-1,4-dibromo-2-butene c. (Z)-1,4-dibromo-2-butene d. (Z)-2,3-dibromo-2-butene ANS: A BIAF 7e Test Bank19. What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 2 c. only 1 and 3 d. only 2 and 4 ANS: B 20. What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 3 c. only 1 and 3 d. only 2 and 4 ANS: B 21. What is (are) the major organic product(s) formed in the following reaction? a. only 1 b. only 2 c. only 3 d. 1, 2 and 3 BIAF 7e Test BankANS: C 22. Which of the following reaction coordinate diagrams explains the formation of different thermodynamic (T) and kinetic products from the same reactants (R)? a. 1 b. 2 c. 3 d. 4 ANS: C BIAF 7e Test Bank23. Which of the following energy diagrams represents the electronic state of the ground state of 1,3- butadiene? a. 1 b. 2 c. 3 d. 4 ANS: A 24. Which of the following energy diagrams represents the electronic state of butadiene after absorption of radiation?