1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound?

Transcription

1 EM 331: hapter 1/2: Structures (Atoms, Molecules, Bonding) 1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound? N 2 N 2 N What hybrid orbitals are used to form the sigma bond between -1 and -2, respectively, in the structure shown? 3 3 N In which of these structures would the sulfur atom be assigned a formal charge of +1? 3 S 3 3 S 3 S 3 S hapter 3: Alkanes 4. There are four different functional groups in the molecule below. Identify the types of functional groups. 2 N N 2 5. The heat of combustion of neopentane is kj/mol; that of pentane is kj/mol. Which statement best describes the relative stability of these two compounds? a. Pentane and neopentane are isomers and therefore exhibit the same stability b. Pentane is more stable than neopentane by 19 kj/mol. c. Neopentane is more stable than pentane by 19 kj/mol. d. Neopentane and pentane are not isomers so no statement can be made regarding relative stability.

2 6. Write the IUPA name for the following: Which Newman projection represents the most stable conformation of 3- methylpentane ( 3 2 ( 3 ) 2 3 ) when viewed down the 2-3 carbon-carbon bond? Which compound will have three peaks of equal height and three valleys of equal depth in a diagram of potential energy vs. angle of rotation for one complete rotation around the - bond? hapter 4: ycloalkanes 9. What factor is responsible for a greater heat of combustion per 2 for cyclopropane than the heat of combustion per 2 for cyclohexane? a. yclohexane has a different hydrogen-to-carbon atom ratio than cyclopropane. b. yclohexane is a strained ring relative to cyclopropane c. yclopropane is a strained ring relative to cyclohexane d. yclohexane has more carbon atoms than cyclopropane. 10. What is the IUPA name for this compound? a. ortho-bromocyclohexanol b. cis-2-bromocyclohexanol c. endo-2-bromocyclohexanol d. trans-2-bromocylohexanol

3 11. Which is the most stable conformation for cis-1-bromo-3-methylcyclohexane? hapter 5: Stereochemistry 12. What is the correct stereochemical description of the relationship between this pair of compounds (identical, constitutional isomers, enantiomers, diastereomers)? 13. Which statement about these Fischer Projections is correct? a. I and II are enantiomers. b. II and IV are identical c. II is a meso compound d. I and II are diastereomers 3 3 I II III IV Which of these molecules are meso isomers? 15. Determine if each of the configurations in each of these two molecules is R or S S

4 16. What is the stereochemical classification of (1S, 2S)-1,2-cyclohexanediol and (1R, 2S)-1,2-cyclohexanediol? a. enantiomers b. diastereomers c. meso compounds d. racemates 17. Which statement is true? a. ompounds with R stereocenters rotate plane-polarized light clockwise. b. For equal concentrations and equal path lengths, solutions of (+) and (-) enantiomers rotate plane-polarized light equally, but in opposite directions c. Racemic mixtures can rotate plane-polarized light either clockwise or counterclockwise. d. Meso compounds can rotate plane-polarized light either clockwise or counterclockwise. 18. Which of the following molecules is the enantiomer of this molecule? ow many stereocenters (chiral centers) are present in this molecule? Which of these molecules could have an enantiomer?

5 21. Which is capable of exhibiting cis-trans isomerism? 3 3 ( 3 ) Which molecule shown below is the same stereoisomer as the one in this Fischer projection? hapter 7: Intro to Alkenes 23. What is the IUPA name for this compound? a. (E)-3,5-dimethyl-2-hexene b. (Z)-3,5-dimethyl-2-hexene c. (Z)-1,2-dimethyl-2-isobutylethylene d. (E)-3,5,5-trimethyl-2-pentene ( 3 ) What would be the stereochemical classification of the major product of this reaction? 3 ( 3 ) 2 a. R-enantiomer b. S-enantiomer c. Achiral d. Racemic

6 25. yclohexene reacts with bromine to yield 1,2-dibromocyclohexane. Molecules of the product would be: a. a racemic form and, in their most stable conformation, they would have both bromine atoms equatorial. b. a racemic form and, in their most stable conformation, they would have one bromine atom equatorial and one axial. c. a meso compound and, in its most stable conformation, it would have both bromine atoms equatorial. d. A meso compound and, in its most stable conformation, it would have one bromine atom equatorial and one axial. hapter 8: Alkene Reactions 26. What set of reagents would convert the alkene in this alcohol as the major product? a. 2, b. B 3 followed by Na, 2 2 c. g(ac) 2, 2 followed by NaB 4 d. followed by Na 27. Draw the product of the following reaction: 1. BD Na, What intermediate is involved in the reaction shown? 3, K 29. The addition of bromine, 2, to the alkene shown will give a. one meso compound b. one pair of enantiomers c. two meso compounds d. four stereoisomers 2

7 hapter 9: Alkynes and Reactions 30. What is the major product isolated from the reaction shown? 3 2 2, gs 4 2 S What reagent(s) can be used to reduce a triple bond to a double bond having Z (cis) geometry (as shown in the figure)? R' R R' R a. Na, N 3 b. NaB 4 c. 2, Pd/a 3 /Pb d. 2, Pd/ hapter 10: Radicals 32. For which free radical can the most resonance forms be written that show the delocalization of the radical? a. b. c. d Which of the indicated sites would most readily undergo hydrogen atom abstraction to generate a radical? What is the expected stereochemistry of the organic product from this reaction? 3 2, light 3 + a. (S)-isomer only b. (R)-isomer only c. equal amounts of (R)-isomer and (S)-isomer d. unequal amounts of (R)-isomer and (S)-isomer

8 35. Which radical is the most stable? hapter 11: Substitutions and Eliminations 36. The reaction of benzyl bromide ( ) with azide ion (N 3 ) is N N 3 + shown in the box. When the benzyl bromide concentration is constant and the azide concentration doubles, the reaction rate is observed to increase by a factor of two. When the azide concentration is held constant and the benzyl bromide concentration doubled, the rate of the reaction doubles. What is the correct rate law for this reaction? a. Rate = k [ ] 2 [N 3 ] 2 b. Rate = k [ ] 4 [N 3 ] 2 c. Rate = k [ ] 2 [N 3 ] d. Rate = k [ ] [N 3 ] 37. What is the structure of the reagent that would yield the two products shown?? What is the expected reaction pathway (E2, E1, S N 2, S N 1) for the following reaction?

9 39. What is the configuration of the substitution product formed from the reaction of K with (R)-1-chloro-1-deuteriobutane ( D)? a. (S)-1-deuterio-1-butanol b. (R)-1-deuterio-1-butanol c. meso-1-deuterio-1-butanol3 d. a racemic mixture of (a) and (b) 40. Put the nucleophiles ( 3, 3, 3 N 2 ) in order, fastest to slowest, for reaction with propyl bromide ( Nuc Nuc). 41. Which alkyl halide would you expect to undergo S N 1 hydrolysis most rapidly? a. ( 3 ) 3 I b. ( 3 ) 3 c. ( 3 ) 3 d. ( 3 ) 3 F 42. Which anion is the most nucleophilic towards methyl iodide in an S N 2 reaction? S What is the major elimination product from the reaction shown? D 3 KtBu 44. What is the product of the reaction shown? 3 D 6 5 KtBu 45. What would be the possible product(s) of the dehydrohalogenation of trans-1- bromo-2-methylcyclohexane? K 3

10 46. Why would concentrated hydrobromic acid be an inappropriate catalyst for the dehydration of alcohols? a. is too weakly acidic to protonate the alcohol. b. The conjugate base,, is a good nucleophile and it would attack the carbocation to form an alkyl bromide. c. is strongly acidic, so the water molecule would not be a good leaving group after protonation of the alcohol. d. would be more like to promote rearrangement of the carbocation intermediate. 47. Which carbocation is not likely to undergo rearrangement? 48. Which alcohol is dehydrated fastest in concentrated 2 S 4? onsider the following typical nucleophilic substitution reaction. The effect of doubling the volume of solvent would be to multiply the reaction rate by a factor of: a. ¼ b. ½ c. 2 d K 3 + K hapter 18: Ethers 50. Which set of products is expected from the reaction shown? 2 3 heat a. b. c. d No Reaction

11 51. What is the product of the reaction shown? Na Which reaction would product phenyl propyl ether? a. b. Na Na c. d Na Which of the following molecules shown below is the product of the reaction of (E)-1-phenylpropene with meta-chloroperbenzoic acid? 3 mpba