KEY I. (28 points) i) NOTE: sp-hybridized carbanions make good nucleophiles for substitution reactions. Product A C C CH 3. Product B.

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1 I. (8 points) Page 1 A. omplete the following as necessary NT: sp-hybridized carbanions make good nucleophiles for substitution reactions NaN N Na Na (optional) i equivalents of Product A Product B a) 1 b) 1 -NMR: signals ratio: 1::9 c) 1 -NMR: signals a) 1 b) 1 -NMR: signals ratio: 1: c) 1 -NMR: signals Would you expect product A in part i to be the major or minor product? minor onsider the following four structures when answering the questions below. ompound ompound D ompound ompound F Write the letter(s) for the compound(s) that......is chiral iv)...has at least one chiral diastereomer iv), i...has at least one diastereomer i,d, v)...has an enantiomer v)...is a unique compound...no other stereoisomers exist F v...is meso v

2 II. ( points) The structure of compound A is shown below Potentially useless inf ormation ompound G G o eq =. kcal/mol Name Page - G o eq(kcal/mol) ( ).1 -( ) A. Draw the two chair conformations for ompound G in the boxes below. Your drawings should clearly show both axial and equatorial positions for any ring atoms that have substituents (be clear in your bond angles!). K eq What can you tell about K eq for the equilibrium as drawn in part A? ircle the correct option. Note: The "Potentially useless information" above will be useful here. K eq >1 K eq <1 K eq =1 annot determine K eq i If the - groups in ompound G were changed to -, would you expect your answer to to change or stay the same? If it changes, what is the new answer? Why? If it does not change, why not? It would change. K eq would be less than 1 due to the loss of hydrogen bonding stabalization with the Gauche groups.. What is the name of ompound G? R (1S,S,S,5R)--tert-butyl-5-methylcyclohexane-1,-diol (1S,S,S,5R)--tert-butyl-5-methyl-1,-cyclohexanediol may use "t-butyl"

3 III. (18 points) Page A. You may recall gliotoxin from your first exam. ere it is again, drawn threedimensionally to show the appropriate stereochemistry for the active natural compound (one of many stereoisomers that can be drawn for this connectivity). Atom a) There are a total of Atom W sources of stereochemistry in this compound. For each of the circled centers (1-),assignthecenterits correct stereolabel in the corresponding box below N S the structure. S N a) Give labels to circled sources of stereochemistry. 1 5 R R Z Z S S 1 Atom Y Gliotoxin 5 Atom Z b) circle all that apply b) The above stereoisomer of gliotoxin has a specific rotation of [ ] D = -5 o. What is D = -5o D = -10o the specific rotation (using the above atom labels) of (1S,S,Z,Z,5R,R)-gliotoxin? D = 5o D = 10o D =0o no way to determine c) The nitrogen atom labeled "Atom W" is not circled as a stereocenter. Given that nitrogen can be a stereocenter, and a lone pair of electrons can count as one of the four "different" groups, why is Atom W not a stereocenter? c) The nitrogen labeled "Atom W" is not tetrahedral. It is sp -hybridized due to resonance with the neighboring carbonyl. Newman projections are often used to show the spatial arrangement of groups in complicated structures. Draw the conformation of the bond between chiral stereocenters 5 and above, using the point of view with carbon 5 in front. Note: you SULD abbreviate the atoms in the rings that are attached to these carbons by using the labels corresponding to the atoms (i.e.w,,y,z) that are directly attached to the bond represented in the Newman, but all other groups should be drawn. Y Z

4 IV. (8 points) A. The following reaction produces a mixture of stereoisomers. i Draw the transition state from the first step in the path leading to ompound J i transition state drawing - ompound Name Page ompound J Draw an energy diagram of the above reaction. Indicate the locations of the starting materials (SM), any intermediates (I), all transition states (), and the products ( and J). SM -First highest pt -&J same level - for &J same level -I for &J same J reaction progress I Provide the complete IUPA name (including stereochemistry, if applicable) for ompound J ompound J (R)--bromo--methylbutane i Draw the Newman projection for the conformation of ompound J shown above, viewing the bond as indicated. Draw the Newman projection for the most unstable, highest energy conformation for this same bond in ompound J (use the same view, and your Newman must be consistent with the one you drew in i.

5 V. (0 points) Page 5 A. Provide the structures for the compounds that are required to complete the following reactions. major regioisomer S (cat.) ignore stereochemistry i N N N ote: ionic product Na Na Note: balance the reaction omplete the following reaction i The two products of the above reaction are best described as being (pts) diastereomers of each other. The products drawn above are the major regioisomeric products. Two other products are theoretically possible, though less likely. Draw them.