Organic Chemistry 3540

Transcription

1 rganic Chemistry 3540 ctober 27, 2004 (6 Pages, 13 Parts) Name 1. (10%) Draw structures of the following showing stereochemistry if appropriate: a. s -butyl alcohol b. isobutyl isopropyl ether c. p-nitrophenoxide ion d. (S)-3-hexanol e. meso-2,3-dihydroxybutane 2. (3%) Determine if the following compound is (R) (S). 3. (8%) Mark each stereocenter (chiral carbon) in the compounds below with an asterisk * AND give the maximum number of possible stereoisomers f each compound. C 2 =CCIC(C 3 )CFC 2 C 2 Pregnenolone

2 4. (14%) Encircle the crect answer: a. Me soluble in water: C 3 C 2 C 2 C 2 C 3 C 2 C 2 C 2 C 3 b. igher boiling point: C 3 C 2 C 2 C 2 C 3 C 2 C 2 C 3 c. Me soluble in water: C 3 C 2 C()C 2 C 3 C 3 C 2 C 2 d. ptically active: 50/50 mixture of two diastereomers 50/50 mixture of two enantiomers e. Enantiomer of F 3 C : C 3 F F C 3 3 C f. ptically active diastereomer: C 3 3 C C 3 g. 1,2-Epoxycyclohexane (cyclohexene oxide) plus aqueous acid yields: h. Stronger acid: C 3 C 2 CF 3 C 2 +1 i. Better leaving group: -SC 3 -S(C 3 ) 2 j. Better nucleophile: -1 I -1 k. Reacts faster in S N 2 reaction: (C 3 ) 3 C C 3 C 2 C 2 C 2 l. Reacts faster in S N 1 reaction: C 3 C 2 C 2 C 2 (C 3 ) 3 C m. Reacts faster in S N 1 reaction: n. Diastereomer of 3 C C 3 3 C C 3 3 C C 3 3 C C 3

3 5. (6%) F each of the following, state if the operating mechanism is S N 1, S N 2, E1, E2, if the mechanism can t be determined from the given data. Reaction is: R-X + Y >? (There are no other functional groups in R.). a. Rate = k [R-X] and the product is an alkene. b. ptically active R-X gives optically active R-Y. c. C 3 C 2 C 2 C 2 -X gives predominantly C 3 C=CC 3. d. (C 3 ) 3 CCXC 3 > (C 3 ) 2 C=C(C 3 ) 2. e. t-amyl iodide and the bromide ion gives t-amyl bromide at the same rate as t-amyl iodide and the chlide ion gives t-amyl chlide. f. (C 3 ) 3 CCXC 3 ---> (C 3 ) 2 CCY(C 3 ) 2 6. (6%) Dehydrohalogenation of the following bromide using alcoholic K goes under E2 conditions. a. Give the structure of the product being careful to show stereochemistry. C 6 5 C 6 5 C 3 b. Give the mechanism of the reaction using the curved arrow notation.

4 7. (6%) Give simple chemical tests which will differentiate between the members of the following pairs. Give the fmulas of the compounds you would ADD and tell what you would SEE. a. b. 8. (7%) Give the mechanism of the following transfmation (curved arrow notation, of course): (7%) Encircle the deactivating groups and underline the tho,para-directs f electrophilic aromatic substitution reactions. N C C 3 C N C 3 C 2 5 CF 3 N 2 N 3 +1

5 10. (12%) utline syntheses of the following compounds starting from acetylene, benzene, ethanol, and methanol and as your only source of carbon atoms. a. b. c. C 2 N 2

6 11. (4%) The - group is an tho,para- direct in electrophilic aromatic substitution. At first glance this seems to be inconsistent with the inductive effect of the electronegative oxygen. owever, the reality of the directive effect of - can be easily explained by considering resonance effects. Draw the key resonance contribut that explains the directive behavi of the - group and note what is so special about this contribut (as compared to the other contributs). 12. (7%) ptically active A, C 6 11, was treated with a solution of KMn 4 and no precipitate fmed. A was treated with alcoholic potassium hydroxide and gave two optically inactive isomers, B and C, C Treatment of B with hot, acidic potassium permanganate gave D, C 3 4, and E, C Treatment of C with hot, acidic potassium permanganate gave F, C 4 6 2, and G, C F had only three peaks in the C-13 nmr spectrum. Give logical structures of A, B, C, D, E, F, and G. 13. (10%) Compare and contrast the S N 1 and S N 2 mechanisms f the hypothetical reaction: R-X + Nu -1 > R-Nu + X -1 by giving the following facts f each mechanism (sht but complete answers are satisfacty): S N 1 S N 2 a. Rate Equation b. Stereochemical utcome c. Relative rates of 1 o vs. 3 o substrate d. Possibility of Rearrangements e. Give mechanisms f each using the curved arrow notation