For each of the pairs shown below, choose the statements that can be used to describe the drawings and their relationship, if a relationship exists.

Transcription

1 I. ( points) ame Page or each of the pairs shown below, choose the statements that can be used to describe the drawings and their relationship, if a relationship exists. (a) (b) and : "heck" any/all descriptions that apply are are are are conformational isomers (conformers) are identical molecules contain at least one R stereocenter (in the pair) represent at least one achiral compound(s) and : "heck" any/all descriptions that apply are are are are conformational isomers (conformers) are identical molecules contain at least one R stereocenter (in the pair) represent at least one achiral compound(s) or each of the compounds shown below: () Identify any sources of stereochemistry by circling the site(s) and providing appropriate stereolabel(s) for each site. If no stereochemistry is present, 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. (a) (b) front: R /Z is not necessary (c) () back: R "heck" all descriptions that apply has an enantiomer has at least one achiral diastereomer has a meso stereoisomer "heck" all descriptions that apply has an enantiomer has at least one achiral diastereomer has a meso stereoisomer "heck" all descriptions that apply has an enantiomer has at least one achiral diastereomer has a meso stereoisomer The MR spectra for B would show : (write in the number) 7 MR signals The MR spectra for would show : (write in the number) 0 MR signals

2 II. ( points) ame Page arbamic acids are extremely versatile organic compounds widely produced and/or used in organic syntheses. In the following reaction scheme, methylcarbamic acid is deprotonated at its most acidic site under basic (catalytic) conditions. In the second step, a decarboxylation reaction occurs to form the products shown, regenerating the base. Provide the missing information for this two-step reaction. Provide the curved arrow mechanism for the proton transfer. methylcarbamic acid Provide the curved arrow mechanism for the second reaction. ΔG to < 0 ΔG to < 0 fast slow verall reaction: Keq >> + + regenerated (iii) ircle the sketch of the energy diagram that most accurately represents the reaction scheme shown above.,, and represent the relative energies of the molecules shown in the boxes above ( represents the product mixture). progress progress progress progress (iv) ketch the transition state for the second step of this reaction. pts all dashed bonds pt each for partial charges Predict the product(s) formed when molecule undergoes the following treatment. optional nbe pts product pt anion equivalent Molecule 5 (similar to above) undergoes substitution to form. The unusual substitution is explained by considering another major resonance contributor for molecule 5. Provide the curved arrow mechanism for the reaction that produces the ionic compound shown. (iii) Draw the transition state for the one-step substitution. curved arrow mechanism 5 (iii) transition state drawing pts all dashed bonds pt each for partial charges

3 III. (8 points) ame Page luticasone propionate (better known as "lonase") is used to treat asthma, allergic rhinitis, and various similar sinus problems. everal chiral stereocenters have been indicated with circles and arrows. Label each with an R or an. Z fluticasone propionate R Label with an or a Z the two double bonds indicated with arrows. pts for each correct R/ label pt for each /Z 0 Provide the requested information for the following reaction, in which is a major product. Draw the starting material ow many other distinct (i.e. different) products would be expected under these reaction conditions? xplain. (catalytic) other: the diastereomer, and the diastereomeric regioisomers (iii) Molecule has: (please fill in each box with the appropriate number to finish the sentence) enantiomer(s) diastereomer(s) 5 stereoisomer(s) 0 meso stereoisomer(s) no partial credit (iv) Draw the two chair conformations for and indicate the K eq for your pair of chairs. s 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. (iv) circle one K eq > = < - pts per error (bond angles, missing, etc.) pts for correct Keq (based on the drawings) if stereochem is wrong, the first chair is all wrong but the second can get points for consistency (each chair worth 5 points) if connectivity is wrong - no points TI I MR TBL

4 IV. (5 points) ame Page onvert name to structure or structure to name as needed. Be sure to include all information on connectivity and stereochemistry in both your drawings and your naming. nd then fill in the missing information about the MR spectrum for each compound. Draw this compound: -,5,5-triethyl--methylcyclohex--ene -if wrong connectivity: 0 -if stereo is wrong but connectivity is right: - pts/ error up to pt each MR ame this compound: ()-,,-trimethylhept--ene pectra taken on this compound should show: 8 MR signals MR signals with ratio :::::: ompounds containing rings offer interesting insight about conformational stability. onsider molecules and B shown below. Draw a ewman projection of the - bond in as shown; view with the in front. connectivity + stereochem + conformation + in order B Draw a ewman projection of the - bond in B as shown; view with the in front. (iii) Draw a ewman projection for the least stable conformation of the - bond in B as shown; view with the in front. connectivity + stereochem + conformation + in order must be eclipsed and consistent with left

5 V. ( points) (iii) (cat.) ame Page 5 The following reactions yield only two different products that share the same molecular formula. These products form in approximately the same concentration, too., showing all information necessary to define the molecule, and describe their relationship by checking the appropriate box. a equivalent l + l l final box only receives credit final box only receives credit final box only receives credit ach of the drawings below shows only the connectivity of a molecule or a set of molecules that share this connectivity. or each, check all the statements that can be used to accurately describe this connectivity and the molecule(s) represented by this connectivity. l l This connectivity represents: "heck" any/all descriptions that apply to this connectivity only unique compound; no stereoisomers exist only enantiomeric compounds only diastereomeric compounds exactly different molecules or more different molecules only optically inactive molecules only optically active molecules This connectivity represents: "heck" any/all descriptions that apply to this connectivity only unique compound; no stereoisomers exist only enantiomeric compounds only diastereomeric compounds exactly different molecules or more different molecules only optically inactive molecules only optically active molecules