2 h; 240 points Signature UM ID # Problem Points Score GSI I 42 II 45 III 35 IV 46 V 36 VI 36 Total 240

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1 hemistry 10 First ame Final Examination Last ame June 5, 01 please print clearly h; 0 points Signature UM ID # PRIT TE FIRST LETTER F YUR LAST AME ERE: Problem Points Score GSI I II 5 III 5 IV V VI Total 0 omplete Lewis structures are required unless you are given other specific instructions. Precision in drawing counts. heck all three-dimensional representations to ensure you are implying an unequivocal direction of bonding. Do not forget to include important features such as nonbonding electron pairs and formal charges when appropriate. Individual point values are given in the corner of each answer space. The exam has pages in addition to this cover page. A pka table is on the last page.

2 ame I. ( points) Page 1 A. For each of the compounds shown below: 1) identify any sources of stereochemistry by circling the site(s) and providing appropriate stereolabel(s) for each site. If no stereolabels can be given, write "none". ) Then choose the statements that can be used to describe that molecule. ) Provide information about the expected MR spectra for those compounds specified. 1 B. Identify and label any source(s) of stereochemistry Identify and label any source(s) of stereochemistry Identify and label any source(s) of stereochemistry l l Identify and label any source(s) of stereochemistry "heck" all descriptions that apply has an enantiomer has at least one chiral diastereomer is a meso compound has at least one achiral diastereomer is optically inactive "heck" all descriptions that apply has an enantiomer has at least one chiral diastereomer is a meso compound has at least one achiral diastereomer is optically inactive "heck" all descriptions that apply has an enantiomer has at least one chiral diastereomer is a meso compound has at least one achiral diastereomer is optically inactive "heck" all descriptions that apply has an enantiomer has at least one chiral diastereomer is a meso compound has at least one achiral diastereomer is optically inactive The MR spectra would show : (write in the number) 1 MR signals The MR spectra would show : (write in the number) 1 MR signals The following reaction produces exactly two organic products in roughly equal amounts. (i) two major products with the same molecular formula are produced - draw each The MR spectra would show : (write in the number) 1 MR signals The MR spectra would show : (write in the number) 1 MR signals (ii) A and B are: Pd- A B iii) This reaction demonstrates (check the best answer) regioselection stereoselection regio- and stereoselection neither regionor stereoselection

3 II. (5 points) ame Page A. The organohalide shown below is toxic and it is synthesized by red algae to keep predators at bay. (a) Find and label all sites that can be given a stereolabel. l l 1 15 (b) For each of the atoms indicated with an arrow above, provide the atom's most reasonable hybridization as well as its electronic (VSEPR) geometry, and its observable geometry (shape). Atom l 1 ybridization Electronic (VSEPR) geom. bs. geom (shape) B. Each of the following transformations yields or uses one organic compound (a single, unique connectivity). Draw this product for each. a) b) 1) a S (cat.) ) l c) d) l /All 1 equiv. l e) f) S (cat.) S (cat.)

4 A. III. (5 points) ame Page onsider the following related compounds (circle the best option for each): i) Which of these compounds contain the longest - bond (indicated)? 1 there is no difference ii) Which of these compounds has the most acidic proton? 1 there is no difference 1 v) Which compound will predominate at a p of.? 1 1 and will be present in equal amounts iii) Which of these compounds will undergo an EAS reaction with the highest rate? 1 there is no difference iv) Which of these compounds will exhibit meta regioselection in EAS? 1 both will neither will B. itrogen can change the reactivity of molecules in a variety of ways. For instance, pyrrole undergoes electrophilic aromatic substitution (EAS) reactions vigorously and with a high degree of regioselection. In fact, bromination of pyrrole requires no Lewis acid catalyst. The following questions address this reaction. pyrrole + i) The reaction diagram shown at left could be used to follow the reaction above. Be sure to show signs for all numbers representing energy changes. Energy A B D Reaction Progress E kcal/mol (a) ow many mechanistic steps occur in this reaction (A to E)? (b) Estimate the ΔG for the E to step (reverse). (c) Estimate the E a (ΔG ) for the to E step (forward). (d) Estimate the ΔG rxn for the reverse (E to A) transformation. (e) What is the E a (ΔG ) for the rate determining step of the forward (A to E) transformation? ii) Draw the most straightforward curved-arrow mechanism for this electrophilic aromatic substitution reaction. Draw and use the best resonance contributor for the carbocation that forms during this reaction. 15

5 A. IV. ( points) ame Page Provide the missing compounds in the proton transfer reaction shown below. Show only the best resonance contributor(s) for both the base and the conjugate acid that form. Estimate the Keq for the reaction. + K eq = 10 x Use your pka table to estimate the Keq for this reaction. + X = B. Each of the following reactions yields only two major products that share the same molecular formula. Draw these products, showing all stereochemistry (if any) clearly, and define their relationship. (a) A and B are: l (cat.) (b) A B E and F are: s (1 equiv) E F (c) Pt and D are: D (d) K G. Draw all organic product(s) that result from the following transformation. G and are: Pd/a quinoline

6 ame V. ( points) Page 5 A. Molecule 1 is best represented using a set of two resonance contributors. 1-A is drawn for you; draw the other all closed shell contributor (atomic formal charges must be between +1 and -1). 1-B 1-A Assuming the hybridization model for all atoms (considering both resonance I am representing: contributors) provide an accurate and complete three-dimensional orbital picture for (circle one) one of the above contributors, using lines, dashes, wedges, and p orbitals (lone or 1-A overlapping) to show the direction of all electrons (or empty orbitals) in your drawing. 1-B All bond angles should reflect the appropriate geometry and hybridization chosen for your drawing. 8 B. For each of the following pairs, circle all the descriptions that apply.. (a) are different molecules are the same molecule are are are are conformers are different molecules are the same molecule are are are are conformers are different molecules are the same molecule are are are are conformers onvert name to structure and structure to name as needed (including stereochemistry) for: (b) l are different molecules are the same molecule are are are are conformers (S,Z)--bromo--methylhexa-1,-diene

7 A. VI. ( points) ame Page When compound 1 is treated with water under mildly acidic conditions, a wide variety of products form without any indication of rearrangement. Draw the missing products, using the information provided. 9 1 and are stereoisomers 1 heat 9 10 and 5 are stereoisomers 5 B. The above treatment of compound 1 also yields some of product. is predicted to form via molecular rearrangement, specifically the sequential formation of three carbocation intermediates. Draw these in the order you would expect them to form, and provide the curved arrows by which each leads to the next. ext rank the relative stabilities of these intermediates; if any have the same stability put them together and circle them. (i) Initial carbocation intermediate and curved arrow(s) to produce the next (ii) Second carbocation intermediate and curved arrow(s) to produce the next 1 (iii) Third carbocation intermediate heat (iv) Stability of intermediates most unstable E most stable. onsider the chemical transformation of the starting material, 7, into 8. (i) (ii) 8 forms (circle one) s alone with its enantiomer with its diastereomer onformational analysis of the bond indicated in 8 reveals that steric considerations are most important. 8 (iii) Using a ewman projection, draw the most stable conformation for the bond indicated in 8. Use the arrow given to view the bond. 5

8 AID (Strongest Acid) l S I l F pk a JUGATE BASE (Weakest Base) -1 l S -7. I l -. F AID S l l l pk a JUGATE BASE S l l l (Weakest Acid) 9 (Strongest Base)

2 h; 240 points please print clearly Dr. Kathleen Nolta Signature UM ID # Problem Points Score GSI I 42 II 44 III 40 IV 43 V 31 VI 40 Total 240

2 h; 240 points please print clearly Dr. Kathleen Nolta Signature UM ID # Problem Points Score GSI I 42 II 44 III 40 IV 43 V 31 VI 40 Total 240 hemistry 10 First ame Final Examination Last ame h; 0 points please print clearly Dr. Kathleen olta ignature UM ID # PRIT TE FIRT LETTER F YUR LAT AME ERE: Problem Points core GI I II III 0 IV V 1 VI 0