Chemistry 261 Exam 2 Practice Fall 2017

Transcription

1 Chemistry 261 Exam 2 Practice Fall 2017 The following practice examination contains 30 questions valued at 3 point/question unless otherwise noted. Wednesday s exam will also contain 30 questions, with an additional 9 points available as bonus/challenge questions Name: ELECTRON DEFICIENT COMPOUNDS AND LEWIS ACID-BASE DEFINITIONS 1. Which of the following is not a Lewis acid? a. AlCl 3 b. 3 O c. FeCl 3 d. SO 3 e. N/A; all of the above will act as Lewis acids ELECTRON DEFICIENT COMPOUNDS AND LEWIS ACID-BASE REACTIONS 2. The amino group on the weak base aniline (anilinium ion pk a = 4.87) is strongly ortho and para directing, activating the benzene ring towards electrophilic aromatic substitution (EAS, chapter 16). owever, when in the presence of the common catalyst for electrophilic aromatic bromination of the benzene ring, Fe 3, the reaction is strongly inhibited, with complex I being formed. The aniline amino group has acted as a. A Lewis acid b. A Lewis base c. A ønsted acid d. A ønsted acid e. An electrophile Complex I

2 NUCLEOPILES, ELECTROPILES, AND LEAVING GROUPS 3. In the reaction between NaCN and propyl chloride to generate cyanopropane (formally butanenitrile) the chloro group acts as a. A nucleophile b. An electrophile c. A Lewis acid d. A Lewis base e. A leaving group NUCLEOPILES, ELECTROPILES, AND LEAVING GROUPS 4. Which of the following is the strongest electrophile? a. C 3 CO 2 C 3 b. C 3 CO 2 c. C 3 OC 3 d. C 3 COC 3 e. C 3 C C Na BRØNSTED-LOWRY ACIDS AND BASES CONJUGATE ACID AND BASE DEFINITION 5. Which of the following is the conjugate base of ammonia? a. N 4 b. N 3 c. N 2 d. N 2 4 e. N/A; none of the above is the conjugate base of ammonia BRØNSTED-LOWRY ACIDS AND BASES CONJUGATE ACID AND BASE DEFINITION 6. Which of the following are ønsted bases in the following equilibrium? 2O 2O O 3O a. 2 O and O b. 3 O and O c. 2 O and 2 O d. 3 O and 2 O e. Only O as water cannot simultaneously be an acid and a base

3 FUN WIT pk a s 7. What is the approximate pk a of hexanoic acid (commonly caproic acid)? a. 2 b. 3 c. 4 d. 5 e. 6 FUN WIT pk a s 8. Which of the following compounds would be deprotonated by potassium tert-butoxide? a. exane b. 1-exene c. 1-exyne d. (b) & (c) e. None of the above FUN WIT pk a s 9. Which of the following compounds would be deprotonated by sodium hydride? a. exane b. 1-exene c. 1-exyne d. (b) & (c) e. None of the above FREE ENERGY AND CEMICAL EQUILIBRIUM 10. Which of the following correctly expresses the relationship between pk a and the standard free energy of dissociation? a. G o a = 2.3RTpK a b. G o a = -2.3RTpK a c. G o a = 10 pk a/2.3rt d. G o a = 10 pk a/2.3rt o e. pk a = 2.3RT G a

4 STRUCTURE-ACIDITY RELATIONSIPS 11. Rank the bold-faced hydrogens in the following compounds from most acidic to least acidic. COO CF 3 O 3 C 3 C C 3 O I II III IV V a. I > II > III > IV > V b. III > V > II > I > IV c. V > II > IV > III > I d. III > I > V > II > IV e. V > III > I > II > IV STRUCTURE-ACIDITY RELATIONSIPS 12. Rank the identified hydrogens from the most acidic to least acidic in the compound shown below a. a > b > c > d b. a > c > d > b c. c > d > a > b d. d > a > c > b e. c > a > d > b

5 STRUCTURE-ACIDITY RELATIONSIPS 13. For the simple hydrides listed below, which is the correct order of decreasing pk a values? a. C 4 > N 3 > 2 O > 2 S > b. > 2 S > 2 O > N 3 > C 4 c. > 2 O > N 3 > 2 S > C 4 d. N 3 > 2 S > C 4 > 2 O > e. 2 S > 2 O > > N 3 > C 4 ACID-BASE REACTION PRODUCT PREDICTION CURVED ARROW APPROAC 14. What is/are the products of the following acid-base mechanism? Mg a. Mg b. Mg C 3 C 3 c. d. Mg C 3 C 3 e. None of the above

6 ACID-BASE REACTION PRODUCT PREDICTION CURVED ARROW APPROAC (IMPLIED) 15. What is/are the products of the following acid-base reaction? a. b. c. Na N N N Na Na N d. Na N e. N/A; There is no acid-base reaction between the reactants shown STRUCTURE AND BONDING IN ALKENES 16. Which of the following unknown acyclic molecules contains no rings or double bonds a. C 5 13 N b. C 5 10 O c. C 6 10 Cl 2 O d. C 7 12 I e. More than one of the above

7 STRUCTURE AND BONDING IN ALKENES 17. For which of the following molecules can resonance give a completely equivalent, noncharge separated form? a. Benzene b. 1,3,5-exatriene c. 1,3-Cyclobutadiene d. 1,3-Butadiene e. More than 1 of the above DOUBLE BOND STEREOISOMERS/CIS-TRANS & E,Z NOMENCLATURE 18. Please draw the structure for (Z)-2-vinyl-2-pentenoic acid DOUBLE BOND STEREOISOMERS/CIS-TRANS & E,Z NOMENCLATURE 19. Please name the following compound, adhering to IUPAC conventions Name:

8 UNSATURATION NUMBER OR INDEX OF YDROGEN DEFICIENCY 20. What is the unsaturation number for the compound immediately below a. 2 b. 3 c. 4 d. 5 e. 6 PYSICAL PROPERTIES OF ALKENES 21. Which of the following will have the highest boiling point a. 1-pentene b. 1-hexene c. cyclopentene d. cyclohexene e. All of the above boil within 5 o C of one another RELATIVE STABILITIES OF ALKENE ISOMERS 22. Which alkene would you expect to be most reactive toward acid-catalyzed hydration? int: resonance possibilities may surprise you a. Styrene (vinyl benzene) b. Toluene (methyl benzene) c. 1-exene d. 2-exene e. Cyclohexene

9 ADDITION OF YDROGEN ALIDES/CARBOCATION STABILITY/CARBOCATION REARRANGEMENTS 23. Which of the following carbocations would not undergo rearrangement? a. C 3 CCC 3 b. C 3 C 3 C 3 CCC 3 c. C 3 C 3 C 3 CC 2 C 3 d. C 3 e. C 3 CC 2 C 3 C 3 CCC 2 C 3 C 3 ADDITION OF YDROGEN ALIDES/CARBOCATION STABILITY/CARBOCATION REARRANGEMENTS 24. Treating 1-methylcyclohexene with 3 O would produce which of the following as the principal product(s)? O O O I II III O O a. I & V b. II c. III & IV d. IV e. I, III, & V IV V

10 ADDITION OF YDROGEN ALIDES/CARBOCATION STABILITY/CARBOCATION REARRANGEMENTS 25. What is the principal product of the following reaction? 2, C 3 O a. O enantiomer b. OC 3 enantiomer c. enantiomer d. 3 CO OC 3 enantiomer e. More than one of the above

11 ADDITION OF YDROGEN ALIDES/CARBOCATION STABILITY/CARBOCATION REARRANGEMENTS 26. Reacting 1-methylcyclopentene with bromine monochloride (Cl) yields which of the following as principal products? Cl enantiomer a. I b. II c. III d. IV e. V C 3 C 3 Cl enantiomer Cl I II III C 3 enantiomer IV C 3 Cl enantiomer V C 2 Cl enantiomer REACTION RATE CONSIDERATIONS 27. Which of the following correctly expresses the relationship between rate and the standard free energy of activation? a. log(rate) = 2.3RT G o b. log(rate) = -2.3RT G o c. log(rate) = - G o /2.3RT d. log(rate) = G o /2.3RT e. ln(rate) = - G o /2.3RT REACTION RATE CONSIDERATIONS 28. iefly, what is the difference between the standard free energy of activation and the standard free energy of dissociation?

12 CATALYSIS/CATALYTIC YDROGENATION OF ALKENES 29. Under usual hydrogenation conditions, how many moles of diatomic hydrogen will react with the compound immediately below a. 2 b. 3 c. 4 d. 5 e. 6 CATALYSIS/CATALYTIC YDROGENATION OF ALKENES 30. Which of the following will convert cyclohexene into cyclohexane? a. 2 /Ni/high pressure b. 2 /Pd/C c. 2 O/Ni d. More than 1 of the above e. All of the above