Note: You must have your answers written in pen if you want a regrade!!!!

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1 NAME (Print): SIGNATURE: hemistry 310M/318M Dr. ent Iverson 2nd Midterm ctober 29, 2009 Please print the first three letters of your last name in the three boxes Please Note: 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. Note: You must have your answers written in pen if you want a regrade!!!!

2 Page Points Total (20) (24) (22) (16) (17) (24) (36) (16) (20) (19) (15) (24) (13) (24) (12) (302) % T Score W (W score + Exam Grade) Total Grade

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!-dicarbonyls N R 2 R' Ethyl ammonium ion!-ketoesters!-diesters Water Alcohols Acid chlorides Aldehydes Ketones Esters 3 N R R R 2 R 2 R 2 R 2 2 R' 2 R' l R 2 R' R' Terminal alkynes R 25 LDA -N(i- 3 7 ) 2 40 Terminal alkenes R 2 44 Alkanes

6 Pg 1 (20) 1. (5 pts) What is the most important question in organic chemistry? Where are the electrons? 2. (10 pts) Write an acceptable IUPA name for the following two molecules. Where appropriate, use E and Z or R and S This will not be graded (3E, 5S, 6E, 8R)-4,5-diisopropyl-3,6,7,8-tetramethyl-1,3,6-decatriene (3E, 5S, 6E, 8R)-3,6,7,8-tetramethyl-4,5-di-(1-methylethyl)-1,3,6-decatriene (3E,5E,7E)-5-isopropyl-2,3,4,8,9-pentamethyl-6-propyl-1,3,5,7-decatetraene (3E,5E,7E)-2,3,4,8,9-pentamethyl-5-(1-methylethyl)-6-propyl-1,3,5,7-decatetraene 3. (5 pts) Draw the structure that corresponds to the following name: (3E,5S,6R,7E)-2,3,4,5,6-pentamethyl-1,3,7-decatriene

7 Pg 2 (24) 5. (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 N N N 6. For the following carbocation: A) State the hybridization state of the indicated atom in the square box provided. In the rectangular boxes, describe the bonds indicated by the arrows in terms of overlap between hybrid orbitals (the valence bond approach). For example, answers might be! sp 3 -sp 3 or " 2p-2p. Note that this part of the question is NT about hyperconjugation. We just want a valence bond description of the bonding in a carbocation structure. (2 pts. each)! sp 2-1s sp 2 NTIE TIS! sp 3 -sp 3! sp 2 -sp 3 B) (6 pts) This part refers to hyperconjugation. n the structure, circle all of the sigma bonds that can take part in hyperconjugation with the carbocation.

8 Pg 3 (22) 7. A) (8 pts) omplete the following structure of the artificial sweetener Nutrasweet TM at p 3.0, the p of soft drinks like Diet oke TM. By adding appropriate numbers of lone pair electrons, atoms, and formal charges to the atoms in the boxes. (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. Next, in the space provided, write the overall charge on each structure at the indicated p. For your reference, here are the relavant pk a values: 3 pk a = N 3 pk a = N * N * 3 Total charge at p Nutrasweet TM at p 3.0 B) (1 pt. each) n the above structure, put an asterisk next to each chiral center. ) (3 pt) Given the number of chiral centers you identified, how many total stereoisomers are theoretically possible for Nutrasweet TM? 2 2 = 4 D) (3 pt) What is the configuration at all the chiral centers in the molecule, R or S? S E) (2 pt) Nutrasweet TM is made of the amino acids Aspartic Acid and Phenylalanine. Are the amino acids in Nutrasweet the same configuration as the configuration of the amino acids most commonly found in all living oganisms on this planet? Yes F) (2 pt) Would you expect the enantiomer or any of the diasterereomers of Nutrasweet TM to taste sweet to humans? No G) (3 pt) At p of 7.0, what is the total charge on the Nutrasweet TM molecule? 0

9 _ (16) pg 4 8. (4 or 6 pts each) Label each chiral center as "R" or "S" and on the line provided state whether the pair of molecules represent two enantiomers, two diastereomers, or the same compound. Draw a circle around any meso compound. A. Relationship: S R Enantiomers S R B. R S Diastereomers Meso S S. S S Diastereomers Meso R S Did you remember to circle any meso compounds?

10 Pg 5 (17) 9. (6 pts) For each acid-base reaction, circle the side of the equation that predominates at equilibrium. In each case identify the stronger and weaker acids by comparing relative stabilities of the anions which are the conjugate bases of the two acids. Equilibrium favors formation of the weaker acid. You will notice this means you circled the side with the more stable anion N + N + 3 S S 3 pk a = 23 pk a = (11 pts. total) Rank the following species in terms of the stated property from 1 to 4 (or 3) as described, 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 alkene: Place a 1 under the most stable (i.e. least reactive) and a 4 under the least stable (i.e. most reactive) (cis) (trans) Stability of carbocations: Place a 1 under the most stable carbocation and a 4 under the least stable carbocation F Relative Acidity: Place a 1 under the most acidic molecule and a 3 under the least acidic molecule. F F F F F F F 1 F F

11 Pg 6 (24) 11. (6 pts each) For each set of reagents, draw the important intermediate or transition state that we discussed in lecture in the box provided. You must show all lone pairs and formal charges on the structures you draw!! Draw all species produced in this step of the mechanism Next, draw arrows on the starting materials to indicate electron flow to generate the intermediate or transition state that you have drawn. If the intermediate or transition state is chiral, you only need to draw one of the enantiomers, not both. Please read these directions again to make sure you know what we want. Note that we are only interested in the first step of the mechanism here, not the whole mechanism! A Intermediate B Intermediate. A. 3 Ac g + g Ac 3 Intermediate D. For this one used dotted lines ( ) to indicate bonds being made or broken in the structure you draw. 3 + B 3 B Transition state

12 Signature Pg. 7 (36) 12. (24 pts.) Read these directions carefully. Read these directions carefully. (It was worth repeating) For the reaction of an alkene with water and a small amount of sulfuric acid shown below, fill in the details of the mechanism. Draw the appropriate chemical structures and use an arrow to show how pairs of electrons are moved to make and break bonds during the reaction. For this question, you must draw all molecules produced in each step (yes, these equations need to be balanced!). Finally, fill in the boxes adjacent to the arrows with the type of step involved, such as "Make a bond" or Take a proton away". MAKE SURE T NTIE TE QUESTINS AT TE BTTM. If an intermediate or product is chiral, you only need to draw one enantiomer for this problem. S + + S Electrophilic addition/add a proton Products Take a proton away Nucleophile Make a bond between a nucleophille and electrophile (4 pts) During the reaction described by the above mechanism, say what happens to the p of the solution The p stays the same because just as much acid is made as is used. (4 pts) Is this reaction catalytic in acid? Yes (4 pts) ne of the above steps involves making a bond between a nucleophile and electrophile. Draw a circle areound the Nuclophile in this step.

13 Signature Pg. 8 (14) 12. A. (4 pts) For the reaction mechanism you drew on the previous page, draw a circle around the energy diagram that best describes your mechanism. Potential Energy X Potential Energy Reaction oordinate Reaction oordinate Potential Energy Potential Energy Reaction oordinate Reaction oordinate B. (4 pts) Now draw an X through the energy diagram that best describes the reaction of an alkene with B 3, BEFRE the chemist opens the flask and adds 2 2 / -. (2 pts each) For the following, circle the capitalized word that best completes the statement. For a reaction that has a favorable motive (thermodynamic driving force) as written, the products are LWER or IGER in energy than the starting materials. A reaction that has greater opportunity (occurs faster) has a LWER or IGER activation energy. A nucleophile will serve as an ELETRN SURE or ELETRN SINK for an arrow that indicates the making of a new bond. An electrophile will serve as an ELETRN SURE or ELETRN SINK for an arrow that indicates the making of a new bond.

14 Pg 9 (20) 13. The following molecule undergoes rearrangment. Draw the first carbocation intermediate in the first box, then the rearranged carbocation intermediate in the second. Include all lone pairs, formal charges, and arrows and draw the products of the reactions in the last box A. (14 pts) + l l 2 carbocation First carbocation intermediate Rearrangement l Not chiral Rearranged Product l 3 carbocation Rearranged carbocation intermediate B. (6 pts) For the following reactions, all of the observed products are shown. Deduce which reagents were used to produce these product mixtures from the starting alkene shown. Whrite those reagents above the arrows given in the boxes. 2 2 S 4 Rearranged product indicating a carbocation intermediate Racemic 1) g(a) 2 2 2) NaB 4 No rearrangement Racemic

15 Pg 10 (19) 14. (3-5 pts each) The following reactions all involve chemistry of alkenes. Fill in the box with the product(s) that are missing from the chemical reaction equations. Draw only the predominant regioisomer product or products (i.e. Markovnikov or non-markovnikov products) and please remember that you must draw the structures of ALL the product stereoisomers using wedges and dashes to indicate stereochemistry. When a racemic mixture is formed, you must write "racemic" under all of the structures EVEN TUG YU DREW ALL F TE STRUTURES. A (not chiral) B. 1. g(ac) NaB 4 (not chiral) B / (not chiral) D. 3 2 Racemic E. 3 l 2 2 l Racemic l

16 Pg 11 (15) 14. (cont.) (3-5 pts each) The following reactions all involve chemistry of alkenes. Fill in the box with the product(s) that are missing from the chemical reaction equations. Draw only the predominant regioisomer product or products (i.e. Markovnikov or non-markovnikov products) and please remember that you must draw the structures of all the product stereoisomers using wedges and dashes to indicate stereochemistry. When a racemic mixture is formed, you must write "racemic" under all of the structures EVEN TUG YU DREW ALL F TE STRUTURES. F. l 2 3 l l 3 l l Racemic Mixture G. 2 2 S 4 Racemic Mixture. 1. B / Racemic Mixture

17 Pg 12 (24) 12. (cont.) (10 pts) The following reactions all involve chemistry of alkenes. Fill in the box with the product(s) that are missing from the chemical reaction equations. Draw only the predominant regioisomer product or products (i.e. Markovnikov or non-markovnikov products) and please remember that you must draw the structures of all the product stereoisomers using wedges and dashes to indicate stereochemistry. When a racemic mixture is formed, you must write "racemic" under all of the structures EVEN TUG YU DREW ALL F TE STRUTURES. G S 4 (catalytic) 3 Racemic (4 or 6 pts each) The following problems are a new format. We turn the tables and give you the product. In the box provided, draw the starting material required to make that product AS TE PREDMINANT NE(S) using the given reagents. When more than one starting material would work, you must draw both. A. or 3 Not hiral B (Racemic Mixture) 3. 1) B 3 2) 2 2 / (Racemic Mixture)

18 Pg 13 (13) 14. (13 pts total) rganic chemistry is a very creative science because there are so many different reactions known that often we are only limited by our imaginations. For example, the same starting alkene can be converte to the different products listed. Deduce the identity of the starting alkene, and write its structure in the box labeled "Starting Alkene". Fill in the boxes containing arrows with the reagents required to produce the given products. I I I Racemic I Starting Alkene 1) B 3 2) 2 2 / l 2 l l l Racemic l

19 Pg 14 (24) 14. (6 pts) Assuming no rearrangements, draw the three different alkenes that can give rise to the indicated racemic mixture of products with reacted with. or 3 or 3 Racemic 14. (18 pts) For the following reaction, draw all possible products including the different regioisomers and stereoisomers. For this part, assume no rearrangement takes place. A) No rearrangement B) In your answer to part A), did you draw any pairs of enantiomers? No ) Is your answer to part A) a racemic mixture? No D) Now draw any additional product(s) you would see upon rearrangement of the intermediate carbocation Rearranged product(s) (not chiral)

20 Pg 15 (12) 15. (12 pts total) The following reaction will generate a number of products. Assume there is enough 2 so that both pi bonds react completely. Note you do not have to draw the products here, we just want you to answer the questions based on the chemistry intuition you have gained so far. excess 2 A. ow many chiral centers will be created in this reaction? 4 B. ow many total stereoisomers are possible given this number of new chiral centers created? 16. ow many stereoisomers will be produced in this reaction? 4 D. In no more than one or two sentences, explain your answer to part. above. The anti addition stereochemistry requirement of this reaction means that at each pi bond only two different stereoisomers will be produced. Because there are two pi bonds, the total number of stereoisomers observed will be 2 x 2 = 4 out of the 16 possible stereoisomers. You did not have to draw them, but these are the four stereoisomers produced for your reference.

Note: You must have your answers written in pen if you want a regrade!!!!

Note: You must have your answers written in pen if you want a regrade!!!! NAME (Print): SIGNATURE: hemistry 310M/318M Dr. ent Iverson 2nd Midterm November 1, 2007 Please print the first three letters of your last name in the three boxes Please Note: This test may be a bit long,