1.5 h; 120 points Signature. Problem Points Score GSI I 23 II 30 III 23 IV 24 V 20 Total 120

Transcription

1 hemistry 0 econd Examination June, 0 First ame Last ame please print clearly.5 h; 0 points ignature For fastest return, if you are in lab this term. LAB GI: UM ID # PRIT TE FIRT LETTER F YUR LAT AME ERE: Problem Points core GI I II 0 III IV V 0 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 6 pages in addition to this cover page. A pka table is on the last page.

2 A. I. ( points) ame Page onsider the substitution reaction in which compound is converted to compound. a Each of the above conformations is stabilized by at least one intramolecular force, but destabilized by another. onsidering all possible factors (steric interactions, electron repulsion, and potential attractive forces), list one stabilizing and one destabilizing factor (specifically describe the atoms/groups involved) under the conformation you have drawn for and. ) Using a ewman projection, draw the conformation of the bond indicated in - be sure to use the view of the bond indicated by the arrow ) Using a ewman projection, draw the conformation of the bond indicated in -be sure to use the view of the bond indicated by the arrow tabilizing force: tabilizing force: Destabilizing force: Destabilizing force: B. Using the following information, construct an energy diagram for the reaction above, label the position of the transition state, and draw the transition state structure: ) kcal ) Draw the transition state structure for the reaction above. ΔG rxn = - kcal/mol E a (ΔG ) = 6 kcal/mol Energy Reaction progress

3 A B D E F II. (0 points) For each of the compounds shown below: ame Page ) 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. "heck" all descriptions that apply "heck" all descriptions that apply "heck" all descriptions that apply "heck" all descriptions that apply "heck" all descriptions that apply "heck" all descriptions that apply The MR spectra for B would show : (write in the number) MR signals MR signals The MR spectra for D would show : (write in the number) MR signals MR signals The MR spectra for F would show : (write in the number) MR signals MR signals

4 III. ( points) ame Page A. Ethinyl estradiol is synthetic steroid used for birth control because it prevents ovulation. Find, circle and label with an R or an all chiral stereocenters that can be assigned a configuration in ethinyl estradiol. Ethinyl estradiol 0 B. When Molecule is treated with a small amount of acid, +, in water, as shown below, the product, Molecule, is formed in a large amount. The reaction is thought to start with the formation of a very stable carbocation intermediate. This entire reaction can be explained using three mechanistic steps, and the acid is regenerated in the process. Draw this complete transformation. Be sure to draw all products for each step, provide all curved arrows, and number your steps. + ) 0 ) Given its connectivity above, provide a name for Molecule. ) ow many different molecules are represented by:

5 IV. ( points) ame Page A. () The following reaction yields four different products that share the same molecular formula. ne of these (A) is provided for you; draw the other three. Be sure to show all the structural information that makes each product unique. l l A 6 () onformational analysis: Draw the two chair conformations for A 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. K eq > = < B. Draw the two structural isomers with molecular formula 7, using the information given. Be sure to draw clearly, and be sure to use all the information given. 7 (R)-,-dimethylcyclopentanol MR signals MR signals with ratio: ::

6 V. (0 points) ame Page 5 A. () omplete the following syntheses using the information provided. Li + Li Li () Each of these products is a unique connectivity: no stereoisomers form. Major regioisomer Minor regioisomer excess 6 B. onsider the one-step transformation shown: heat + ) Draw the curved arrow mechanism for this transformation, and ) draw the transition state that forms. curved arrow mechanism + transition state

7 AID (trongest Acid) l I l F pk a JUGATE BAE (Weakest Base) - l -7. I l -.6 F AID l l l pk a JUGATE BAE l l l (Weakest Acid) 9 (trongest Base)