diene. If stereoisomeric mixtures form, indicate by drawing one and writing "+ enantiomer" and/or "+ diastereomer" in the box.

Transcription

1 I. (9 points) Page A. Consider how varying the conditions of a reaction can vastly influence the rate of a reaction as well as the product(s) formed. First draw the product(s) that form in the reference reaction, then evaluate how the rate will change with the changes suggested, assuming the mechanistic path is unchanged. If SM is changed to (a) SM C If SM is changed to (b) LiCN DMF CN If SM is changed to If DMF is changed to SM (c) I C C Provide the missing information C If [C ] is doubled If I is tripled C-NMR: C-NMR: Pt ) ) Zn

2 Page II. ( points) A. Draw all the product(s) expected to form in the following halogenation reaction involving a diene. If stereoisomeric mixtures form, indicate by drawing one and writing "+ enantiomer" and/or "+ diastereomer" in the box. C C C C equiv. (a) C-NMR: 5 (b) C-NMR: C C C C C C C C As expected, a halonium ion forms in the first (rate-determining) step in the transformation shown. Since the conditions used are very mild, a final proton-transfer step is needed to yield a neutral organic product, causing the p of the reaction mixture to drop slightly. Using this information, draw a complete, stepwise curved arrow mechanism for the formation of the product given. return arrow can go to either C of the pi bond Ph may be used for the top and bottom Ph groups pts intermediate (all or nothing with charge) points for each mechanism - no partial, all arrows Phenylselenium bromide is a common source of electrophilic selenium that also provides a source of nucleophilic bromide. These reagents react in addition reactions with the same regioselection and stereoselection of halogenation reactions. Draw one product predicted to form in this reaction and indicate whether others are expected by writing "+ enantiomer," "+ diastereomer" or "+ stereoisomers" in the box. Se Se + enantiomer C Connectivity +, stereochem + + for enantiomer

3 III. (0 points) Page In this set of reaction predictions, it has already been determined that two different (but related) neutral organic products form (please ignore byproducts). Draw both products, clearly showing in your drawing all structural and/or stereochemical information that distinguishes them from each other. Then discuss the optical activity of these products and their relationship. must have correct products to A. receive credit for analysis S (cat.) equiv. excess must show the cis and trans must have correct products to receive credit for analysis ne ne ne D. P heat ne E. ) B ) /Na ne

4 IV. (8 points) Name Page A. Complete the following synthetic pathway by supplying the missing structures. Na Na Pd/BaS Pb Under acidic conditions, isomerizations, especially those involving carbocation rearrangements, are quite common. The mechanism proposed for the following transformation (similar to hydration/dehydration) can be deduced using the one complete intermediate that is provided. Use this guidance to provide the missing intermediates and the complete curved-arrow mechanism the production of clovene from caryophyllene; you may ignore stereochemistry. ydronium ion and water are available for those steps requiring external agents. step mechanism caryophyllene clovene complete the intermediate and provide the step mechanism complete the intermediate and provide the step mechanism caryophyllene 5 5 acidic conditions clovene pts each intermediate pts each mechanistic step (all or 0 for mech arrows) this intermediate is complete; provide the step mechanism 6

5 V. ( points) Name Page 5 In contrast to a previous problem, each of the following reactions yields a single distinct organic product. Draw this product clearly, showing connectivity and stereochemistry (when it exists) unambiguously. ) N (b) A. (a) S C C CN ) C Na ) C ) Na ) NaCN Na/N D. (a) Bimolecular elimination yields a single product in each of the following two cases. K KMn (i) Draw the complete (substituted ring atoms with axial and equatorial bonds clearly drawn) chair conformation favored for this reaction and show the curved arrow mechanism. pts chairwrong connectivity or stereochem means 0 pts for chair pts mech; need to have axial and need all arrows for those pts must be the meso compound and must be drawn in D (ii) The single product 7 (b) N N a big, strong base (iii) Give the complete IUPAC name (with stereolabels as needed) for the starting material - pts/error in label, group name, main chain or numbering (S,S)--bromo-,,-trimethylhexane (i) The single product (Z) C (ii) Draw a Newman projection showing the conformation favored for this type of reaction. The C with the leaving group should be in front. C wrong connectivity 0 stereochem wrong 0 conformation wrong +