HO 1:1 1:1. Amines, like cathine, are often excellent nucleophiles Provide the requested information for the following one-step reaction scheme.

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1 I. (4 points) A. athine (shown at right) is a psychoactive amphetamine drug obtained from the plant atha edulis (also known as khat). View down the 1 - bond indicated ( 1 being the front atom), and answer the following questions. [α] D = + 4 ame Page 1 cathine 1 view (a) Draw a ewman projection of the 1 - bond in cathine in the conformation shown; view with the 1 in front. (b) Maintaining the same view for this bond, and taking into account steric and intramolecular forces, draw the most stable eclipsed conformation expected for this bond in cathine. iefly explain your answer. B. 4 (c) Given cathine's optical activity, predict the optical activity for each of the following molecules or mixtures. If it cannot be determined, write "unknown". [α] D = (a) 1:1 1:1 mixture mixture 1 [α] D = 1 [α] D = 1 [α] D = 1 Amines, like cathine, are often excellent nucleophiles Provide the requested information for the following one-step reaction scheme. Provide the curved arrow mechanism for the reaction predicted to occur (b) Provide product(s) - balance your reaction 6 l l 4 (c) Provide a complete transition state drawing for this reaction 4

2 II. (4 points) ame Page A. For each of the following structural pairs, check all the descriptions that can be used to describe the relationship between the molecule(s) represented. (a) l l l l different molecules same molecule stereoiosomers s (b) different molecules same molecule stereoiosomers s conformers 4 4 conformers B. For each of the following molecules, check all the descriptions that can be used to describe it and its related molecules. (a) (b) (c) (d). onsider the energy diagram provided when answering these questions. Energy, G B D F (a) Using positional labels, how would you calculate the E a (ΔG ts ) of the rate determining step for the formation of G from A? (c) Using positional labels, how would you calculate the ΔG for the rate determining step in the formation of A from G? A E G (b) What can you conclude about the K eq for the formation of G from A? (d) Using positional labels, identify the intermediates that form in the forward reaction. reaction coordinate

3 ame III. (4 points) Page A. You might remember some of those antibiotics that were introduced to you on the first exam. ne of them, clavulinic acid, is often used in conjunction with amoxicillin in a treatment called co-amoxiclav. These drugs are shown for you here for your stereochemical analysis. ircle and label every chiral (tetrahedral) stereocenter in amoxicillin. ircle and label every chiral center and double bond stereosite in clavulinic acid. amoxicillin clavulinic acid co-amoxiclav: aka augmentin 14 B. omplete the following multi-step synthesis by filling in the missing chemical intermediates, using the information provided to guide you. (a) Draw the two isomeric products 6 1 MR signals 5 1 MR signals l 1 equivalent first transformation What best describes the relationship between these two initial products s 5 second transformation A subsequent addition reaction using either or both product(s) from the first reaction yields another pair of isomeric products. Draw these two distinct products. (b) Draw the two isomeric products 6 1 MR signals 5 1 MR signals What best describes the relationship between these two final products s 5

4 IV. ( points) ame Page 4 Each of the following reactions demonstrates regioselection (i.e. only one product A. connectivity is observed). Draw a product that is selected to form, showing connectivity (and stereochemistry when it applies) clearly and unambiguously. Then state how many other distinct products (with the same connectivity, stereoisomers of the product you drew) will form. I 1 equivalent Draw regioselected product other product(s) that is/are and stereoisomer(s) of this will form fill in a number here 4 (cat.) Draw regioselected product other product(s) that is/are and stereoisomer(s) of this will form fill in a number here 4 (cat.) Draw regioselected product other product(s) that is/are and stereoisomer(s) of this will form fill in a number here B. Ring formation is often a consequence of reactions occurring in molecules with complementary reactive sites. Provide the most straightforward curved arrow mechanism for this addition reaction which involves a ring-forming second step, using (and regenerating) the appropriate acid indicated for these conditions. 4 (cat.) 14

5 V. (5 points) ame Page 5 onsider the hydration reaction (addition of water) involvng the starting material, M, shown at right. Draw in the missing product and continue your analysis by answering the questions below. M 4 (cat.) P1 + (a) Draw P (b) ame the starting material, M, providing stereolabels as required: 4 P1 and P are stereoisomeric compounds and they form in different concentrations. (c) Draw the two chair conformations for P1 and indicate the K eq for your pair of chairs. As always, be sure to clearly and accurately show the axial and equatorial positions for all substituted ring atoms. You do not have to show axial and equatorial hydrogen atoms for unsubstituted ring atoms. circle one K eq > 1 = 1 < 1 1 (d) an you explain why P1 forms in a greater concentration over P? M (e) heck all the descriptions that apply to M: P1 (f) heck all the descriptions that apply to P1:

6 AID (trongest Acid) l I l F pk a JUGATE BAE (Weakest Base) -1 l -7. I l -4.6 F AID l l l pk a JUGATE BAE l l l (Weakest Acid) (trongest Base)