You must have your answers written in PERMANENT ink if you want a regrade!!!! This means no test written in pencil or ERASABLE INK will be regraded.

Transcription

1 AME (Print): SIGATURE: hemistry 310M/318M Dr. ent Iverson Final exam December 8, 2010 Please print the first three letters of your last name in the three boxes Please ote: This test may be a bit long, but there is a reason. I would like to give you a lot of little questions, so you can find ones you can answer and show me what you know, rather than just a few questions that may be testing the one thing you forgot. I recommend you look the exam over and answer the questions you are sure of first, then go back and try to figure out the rest. Also make sure to look at the point totals on the questions as a guide to help budget your time. You must have your answers written in PERMAET ink if you want a regrade!!!! This means no test written in pencil or ERASABLE IK will be regraded. Please note: We routinely xerox a number of exams following initial grading to guard against receiving altered answers during the regrading process. FIALLY, DUE T SME UFRTUATE REET IIDETS YU ARE T ALLWED T ITERAT WIT YUR ELL PE I AY WAY. IF YU TU YUR ELL PE DURIG TE EXAM YU WILL GET A "0" MATTER WAT YU ARE DIG WIT TE PE. PUT IT AWAY AD LEAVE IT TERE!!!

2 Total Pts T Score W Total Grade (W score + Exam Grade) % Page Points (26) (14) (19) (19) (16) (27) (27) (13) (19) (26) (42) (30) (21) (14) (14) (10) (16) (16) (8) (8) (385) 20

3 onor ode The core values of the University of Texas at Austin are learning, discovery, freedom, leadership, individual opportunity, and responsibility. Each member of the University is expected to uphold these values through integrity, honesty, trust, fairness, and respect toward peers and community. (Your signature)

4 ompound pk a ydrochloric acid -l -7 Protonated alcohol R ydronium ion Acetic acid Ammonium ion β-dicarbonyls R 2 R' Ethyl ammonium ion β-ketoesters β-diesters Water Alcohols Acid chlorides Aldehydes Ketones Esters R R R 2 R 2 R 2 R 2 2 R' 2 R' l R 2 R' R' Terminal alkynes R 25 LDA -(i- 3 7 ) 2 40 Terminal alkenes R 2 44 Alkanes

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6 ere is a page in which you could write down your roadmap if you would like

7 Pg 1 (26) 1. (4 pts) What is the most important question in organic chemistry? Where are the electrons? 2. (10 pts) Amides are best represented as the hybrid of three contributing structures. Draw the second and third important contributing structures in the spaces provided, including all lone pairs and formal charges. For the two structures on the left in each problem, use arrows to indicate the movement of electrons to give the structures you drew. There is no need to draw any circles around any of these contributing strucures. You might want to read these directions again to make sure you know what we want 3. (1 pt. each ) n the following structure, indicate the hybridization state of each atom indicated. sp sp 3 sp 2 sp 2 sp 3 3 sp 2 4. (1 pt. each )n the following structure, describe the bonds indicated in terms of overlap between hybrid orbitals (the valence bond approach). For example, an answer might be σ sp 3 -sp 3 σ sp 3 -sp 2 σ sp 2 -sp 2 σ sp 2-1s π 2p-2p σ sp 2 -sp 2 π 2p-2p

8 Pg 2 (14) 5. (14 pts) Shown below are three different amino acids. At the p values indicated, draw the predominant species at each indicated p value BY DRAWIG ALL ATMS, ALL LE PAIRS, AD ALL FRMAL ARGES. (You do not have to add anything such as atoms to atoms not drawn in the boxes.) This problem is testing your understanding of the relationship of protonation state to p to pka values for certain functional groups we have discussed. ext, in the spaces provided, write the overall charge on each structure at the indicated p. For your reference, here are the relevant pka values: 3 pk a = pk a = pk a = 0.5 p = 7 Total charge on molecule: 0 p = 2 Total charge on molecule: 1

9 Pg 3 (19) 6. (19 pts total) The following molecule contains a guanidine group. The guanidine group can add a proton to create a resonance stabilized cation. Draw the three most important contributing structures, making sure to show all lone pairs and formal charges. Draw arrows on the structures to indicate the movement of electrons required to produce the next contributing structure. (f the four contributing structures, only the structure on the right will not have arrows) 3 Guanidine group Amines will also react with protons as shown. 3 2 Amine 3 (5 pts) Predict which will be easier to protonate (i.e. is more basic), the guanidine or amine. In no more than two sentences, explain your answer. The guanidine group is much easier to protonate than the amine because the protonated guanidinum delocalizes the positve charge through resonance, and the positive charge on the amine is localized entirely on the atom.

10 Pg 4 (19) 7. (1 pt. each) Fill in the following with the word or words that best completes the statements. Moving charge creates a magnetic field. Atomic nuclei with an odd atomic mass or odd atomic number have a quantum mechanical property called. spin The difference in energy between the +1/2 and -1/2 spin states of a 1 nucleus is proportional to the magnetic field strength. Resonance in MR refers to the phenomenon of absorption of energy when a nuclear spin "flips". A nucleus with more electron density around it will be shielded more from the external magnetic field, a phenomenon that results from the small but significant magnetic field created when the electron density circulate (i.e. move) due to the external magnetic field. An MRI image is a picture of the relative density of atoms in the tissues being imaged, and especially the amount of water and fat because these two types of molecules have the greatest proportion of atoms in them. 1 1 For either the MR experiment in the laboratory or the acquisition of an MRI image in the clinic, the sample or patient is placed in a strong magnetic field, then the absorption of energy is measured as nuclear (or 1 nuclei) spins flip from the +1/2 to the -1/2 spin states. Running, swimming, biking, etc. every weekend for the rest of your adult life is the best way to stay fit, the secret to true success in life. (otice you cannot get this one wrong unless your activity involves a couch!!!!!!!)

11 Pg 5 (16) 8. (16 pts. total) Rank the following species in terms of the stated property from 1 to 4 with intermediate numbers to rank the species of intermediate stability activity. Please make sure you know what we want, as you will get no credit if you get the numbers backwards! Stability of carbocations: Place a 1 under the most stable carbocation and a 4 under the least stable carbocation Relative Acidity: Place a 1 under the most acidic molecule and a 4 under the least acidic molecule. F S F S F Radical Stability: Place a 1 under the most stable radical and a 4 under the least stable radical Reaction with nucleophiles: Place a 1 under the molecule that is most reactive in an S 2 reaction and a 4 under the molecule that is least reactive in an S 2 reaction. l l l I

12 Pg 6 (27) 9. (5 or 7 pts each) The following reactions all involve chemistry of alkyl halides. Fill in the box above the arrow with the mechanism that will be followed (S 2, E2, etc.). Then draw only the predominant product or products and please remember that you must draw the correct stereoisomers. For S 1/E1 reactions you must draw all significant products (including all stereoisomers). A. S 2 + B. S 2 +. l S 1 / E1 + D. E2 + E. S 2 +

13 Pg 7 (27) 10. (27 pts total) n the line provided, state the stereochemical relationship between each pair of molecules: enantiomers, diastereomers, or the same molecule. I recommend you assign R and S to each chiral center to help answer this question. ircle all meso compounds. Relationship R S Enantiomers l R R l l R R l Same Molecule l S R Meso l l R R l Diastereomers ow that your stereochemistry Mojo is warmed up, here is a reaction that has a variety of products. Draw all products you would expect from the following reaction. Use wedges and dashes to show the different stereoisomers created. Write if appropriate. 2 2 Racemic

14 Signature Pg. 8 (13) Shown below are four different energy diagrams. Each is labeled with a letter. Use these letters to answer questions at the bottom of the page, and on the next TW mechansim pages. Potential Energy A Potential Energy B Reaction oordinate Reaction oordinate Potential Energy Potential Energy D Reaction oordinate Reaction oordinate 11. (13 pts.) For the reaction shown below, fill in the details of the mechanism. Draw the appropriate chemical structures and use arrows to show how pairs of electrons are moved to make and break bonds during the reaction shown. Draw all non-bonded electrons as dots around the appropriate atoms and include all formal charges. MAKE SURE T FILL I TE BX AT TE BTTM The reaction diagram from page 8 that best describes this reaction is: A Energy Diagram Letter TIE TIS Product(s)

15 Pg 9 (19) 12. (19 pts.) Read these directions carefully. Read these directions carefully. (It was worth repeating) For the following two reactions, fill in the details of the mechanisms. Draw the appropriate chemical structures and use arrows to show how pairs of electrons are moved to make and break bonds during the reaction. Make sure to show all lone pairs and all formal charges. Indicate stereochemistry where appropriate. Draw all products of each step. IF A RAEMI MIXTURE F ITERMEDIATES IS FRMED, YU LY EED T DRAW E EATIMER BUT WRITE RAEMI. IF A RAEMI MIXTURE F PRDUTS IS FRMED DRAW BT EATIMER PRDUTS AD WRITE RAEMI! In the boxes provided next to the arrows, state what kind of mechanistic element is being described, i.e. make a bond, etc. 3 add a proton 3 make a bond 3 take a proton away 3 Products The reaction diagram from page 8 that best describes this reaction is: Energy Diagram Letter TIE TIS

16 Pg 10 (26) 13. (22 pts.) Alcohols will react similar to water in most reactions. For the following reaction, fill in the details of the mechanism. Draw the appropriate chemical structures and use arrows to show how pairs of electrons are moved to make and break bonds during the reaction. Make sure to show all lone pairs and all formal charges. Indicate stereochemistry where appropriate. Draw all products of each step. In the boxes provided next to the arrows, state what kind of mechanistic element is being described, i.e. make a bond, etc. IF A RAEMI MIXTURE F ITERMEDIATES IS FRMED, YU LY EED T DRAW E EATIMER BUT WRITE RAEMI. IF A RAEMI MIXTURE F PRDUTS IS FRMED DRAW BT EATIMER PRDUTS AD WRITE RAEMI! In the boxes provided next to the arrows, state what kind of mechanistic element is being described, i.e. make a bond, etc. + l l make a bond Racemic l l 3 make a bond l 3 3 Racemic 3 l 3 take a proton away 3 l Racemic Products The reaction diagram from page 8 that best describes this reaction is: Energy Diagram Letter Did you remember to draw both product enantiomers? TIE TIS

17 Pg 11 (42) 14. (3 or 5 pts each) For the following, complete the reactions with the predominant product or products. You must indicate stereochemistry with wedges and dashes. You must draw all stereoisomers produced as predominant products and write "" under the structures when appropriate. Assume no rearrangments take place. l l l l l 2 2 Pd 3 3 hν RR 1) B 3 1) g(ac) 2 2 2) 2 2 / 2) ab S 4 (cat.) BS hν S 4 (cat.) I 3 2 I I

18 Pg 12 (30) 15. (3 or 5 pts each) For the following, complete the reactions with the predominant product or products. You must indicate stereochemistry with wedges and dashes. You must draw all stereoisomers produced as predominant products and write "" under the structures when appropriate. Assume no rearrangments take place. l l l 2 2) 1) a 2 2 eq. l 2 2 Lindlar's catalyst 2 eq. 1) (sia) 2 B 2) 2 2 gs 4 2, 2 S 4 3 S 3 S l P 3 P 2 S 4 (cat.)

19 Pg 13 (21) 16. (3 or 5 pts each) For the following, complete the reactions with the predominant product or products. You must indicate stereochemistry with wedges and dashes. You must draw all stereoisomers produced as predominant products and write "" under the structures when appropriate. Assume no rearrangments take place. 3 1) s 4 2) as 3, ot!

20 Pg 14 (14) 16. (7 pts each) For the following sequences of reactions, work through all the different steps and then write the final product(s). Assume only the predominant product is formed at each step. You must indicate stereochemistry with wedges and dashes. You must draw all stereoisomers produced as predominant products and write "" under the structures when appropriate. Assume no rearrangments take place. 1), RR, hν 2) a 3) 2, 2 S 4, gs 4 1), RR, hν 3) 2, 2 S 4, gs 4 2) a This next one may look simple, but it is not. You might consider saving it until the end!! 1) 3 2) BS, hν 1) 3 2 E2 2) BS, hν

21 Pg 15 (14) 17. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned provided that the product(s) you draw for each step is/are the predominant one(s). Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction. You must draw all stereoisomers formed, and use wedges and dashes to indicate chirality at each chiral center. Write when appropriate. A) (7 pts)? 2 2 Lindlar's catalyst 2 a 2 meso B) (7 pts)? 2 hν tbuk 1) s 4 2) as 3, 2

22 Pg 16 (10) 17. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned provided that the product(s) you draw for each step is/are the predominant one(s). Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction. You must draw all stereoisomers formed, and use wedges and dashes to indicate chirality at each chiral center. Write when appropriate. For this one, all of the carbon atoms in the product must come from the starting material shown. ) (10 pts)? 3 or R R 3

23 Pg 17 (16) 17. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned provided that the product(s) you draw for each step is/are the predominant one(s). Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction. You must draw all stereoisomers formed, and use wedges and dashes to indicate chirality at each chiral center. Write when appropriate. For this one, all of the carbon atoms in the product must come from the starting material shown. D) (16 pts)? tbuk 2 Lindlar's catalyst 2 a 2 1) 3 a 2 2) Mild acid

24 Pg 18 (16) 17. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned provided that the product(s) you draw for each step is/are the predominant one(s). Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction. You must draw all stereoisomers formed, and use wedges and dashes to indicate chirality at each chiral center. Write when appropriate. For this one, all of the carbon atoms in the product must come from the starting material shown. E) (16 pts)? 2 hν 2 hν tbuk 2 S 4 (catalytic) tbuk 1) B 3 2) 2 2,

25 Pg 19 (8) 18. (8 pts) The key paradigm of organic synthesis is that individual functional groups react the same in complex molecules as they do in simple ones. The following transformations were used to construct complex molecules of interest in medicine and biology. In the space provided, fill in the reagents we have learned this semester that would bring about the desired reactions. R 3 From the synthesis of analogs of leukotriene A 4, 4, and D 4 Journal of the American hemical Society, 1980, 102, / Lindlar catalyst P R R 1) s 4 2) as 3 / 2 3 R' 3 From the synthesis of 11-desoxyprostaglandins R' Journal of rganic hemistry, 1974, 39, 256.

26 Pg 20 (5) 19. (5 pts) ere is an apply what you know question to finish the semester. You have not seen this reaction, but you know enough to get it correct. If you do get it correct, trumpets will play a fanfare!!! Write the product or products of the following reaction. 3 1) 2) Very mild acid 3 In only one sentence, explain your reasoning. TIE TIS The alkyne anion is a good nucleophile so it will react at the less hindered carbon of the expoxide analogous to (A new carbon-carbon bond...trumpet fanfare!!!) ave a glorious and relaxing holiday. Remember to run every chance you get!!