CH Organic Chemistry I (Katz) Practice Exam #2- Fall 2015 (With Answers)

Transcription

1 rganic hemistry I (Katz) Practice Exam #2- all 2015 (With nswers) Name: Score: Part I - hoose the best answer and write the letter of your choice in the space provided. 1. The Newman projection at the right represents: ) 2,3-dimethylbutane ) isopentane ) 2,2,3-trimethylbutane ) 2,2-dimethylbutane 2. Given the following values for bond dissociation energies the absolute numerical value (ignoring the algebraic sign) of Δ (in kj/mol) for the reaction 3-r + N3 ---> 3-N2 + r is: ) 1343 ) 308 ) 194 ) The order of thermodynamic stability of alkyl carbocations, from most stable to least stable is ) 1º>2º>3º>methyl ) 2º>3º>methyl>1º ) methyl>1º>2º>3º ) 3º>2º>1º>methyl 4.The enantiomer of (R)-2-bromobutane: 3 3 ond r-r r N r N2-449 ) may be either (R)- or (S)-2-bromobutane ) cannot be (S)-2-bromobutane E (kj/mol) ) must be (S)-2-bromobutane ) is a mixture of (R)- and (S)-2-bromobutane The following structure represents a compound that : ) is optically inactive and meso ) is optically active and meso ) ontains no chiral carbons ) is optically active and dextrorotatory Is the following compound R or S? 2 3 ) R ) S ( 3 ) 3 ( 3 ) 2

2 7. f the following structures, those structures capable of optical activity are: r r r r r r r r r r V W X Y Z ) (None are capable of optical activity.) ) only V and X ) only W, Y, and Z ) only W and Z 8. The IUP name of the compound at the right is: ) 3-chloro-4-fluoro-2,6-dimethylheptane ) 4-fluoro-5-chloro-2,6- dimethylheptane ) 2-chloro-3-fluoro-1,1,5,5- tetramethylpentane ) 3-fluoro-2-chloro-1,1,5,5- tetramethylpentane 9. The diagram at the right represents: ) the rate-determining step of an Sn2 reaction ) the rate-determining step of an Sn1 reaction ) the final, fast step of an Sn1 reaction ) the transition state of the rate-determining step of an Sn2 reaction Questions 10 and 11 refer to the following three compounds: 10. hoose the thermodynamically most stable isomer. ) ompound 1 ) ompound 2 ) ompound hoose the thermodynamically least stable isomer. ) ompound 1 ) ompound 2 ) ompound ow many stereocenters are present in the following compound? ) 1 ) 2 ) 3 ) 4 l

3 13. In the reaction shown below, the carbon bonded to r was originally which carbon?? ) arbon ) arbon ) arbon ) arbon 14. Which of the following are polar aprotic solvents? ) 1 and 3 3 ) 2 and 4 3 ) 1, 2, and N ) 2, 3, and Which of the following sets of conditions would most likely produce an enantiomerically pure product through complete inversion at a chiral center? ) reaction of strong base with a secondary alkyl iodide in methanol ) reaction of a weak base with a tertiary alkyl iodide in water ) reaction of a strong nucleophile with a primary alkyl bromide in MS ) reaction of a strong nucleophile with a secondary alcohol in water 16. f the following compounds, r? r 3 I l 3 2 r I 2 3 r 3 the total number of E isomers represented is: ) 4 ) 3 ) 2 ) The incorrect IUP name among the following is: ) 4-methylcyclobutene ) 5-bromo-2-chloro-2-hexene ) 3-ethyl-3-hexene ) 3,4-dimethylcyclopentene

4 Part II - Isomers - lassify the following compounds by choosing one of the following terms : ) Identical ) onstitutional Isomers ) enantiomers ) diastereomers l and l l l l l and and 2 3 l and 2 l 3 3 ischer projections Part III - Thermodynamics -Matching - Place the letter corresponding to the term in the blank to the left of the definition.. transition state. standard Gibbs free energy change. endergonic reaction E. exergonic reaction. activation energy. reactive intermediate 22. species that lies at an energy minimum between steps in a reaction, 23. The energy needed by reactants to reach the transition state. E 24. reaction where ΔGº is negative. 25. n intermediate in which bond-breaking and bond-making are taking place. Use the following reaction progress diagram to answer the following questions. Energy 26. The transition state is found at what point on the diagram (hoose,,,) Reaction progress 27. The energy of activation is indicated by which quantity on the diagram (hoose,,,) 28. The reaction free energy change is indicated by which quantity on the diagram (hoose,,,)

5 Part IV - Questions related to conformations. 29. raw a line structure for the compound at right and provide a name for the compound l 3 l (R) 3-chloro-2,2,4-trimethylpentane 30. raw the two chair conformations that are present in a sample of this compound: Which conformer in problem 30 is the most stable? Part V - Questions related to reaction mechanisms. 32. raw the product (s) resulting from the following movement of electrons: a. b

6 33. dd arrows to the reactant (s) to show the mechanism of the following processes: a b. Part VI-Provide IUP names or structures which correspond to the following structures or names on't forget to indicate stereochemistry r 3 l r 3 3 r l (E)-2,3-dichloro-2-hexene 1,5,5-trimethylcyclopentene 36. (Z)-3-isopropyl-2-hexene 37. 1,3-dibromo-4-ethylcyclohexene r r