I. (2 points) ame Page itrogen atoms in amines can undergo substitution reactions repeatedly under mildly basic conditions. Provide the structure of the starting amine and supply the missing reagent(s). starting amine under mildly basic conditions p > 2 equivalents equivalents ofmann eliminations involve bulky nitrogen leaving groups (like the positively charged nitrogen group seen in the product above). Because of the size of the leaving groups, less substituted alkene products are favored. Compound yields two structurally isomeric alkene products when treated with a big bulky base, one at much higher concentration than the other; draw each in the appropriate box. (i) ofmann favored product C C 2 (iii) Draw a ewman projection of the C -C 2 bond in Compound in the conformation that is favored to undergo elimination; view with the C in front. elimination products (ii) minor product ( ) (Z) wrong connectivity 0 stereochem wrong 0 conformation wrong 2 5 If Compound 2 (below) was used in the above reaction, how might things change? 2 C (i) What is the relationship between Compound and Compound 2? (ii) Would the same two elimination products be formed in the same relative amounts when Compound 2 is used in the reaction above? Explain your answer, and if different product(s) are formed you should draw them. (E) diastereomers 2 Same selection/ratio but both products are different in stereochem from the difference in 2's chiral center, leading to different chiral center AD different anti alignment. (2 pts for explain) 2 pts for each product 6
ame Page 2 II. (29 points) Provide the missing materials for each of the following reactions. If you are providing reagents, be sure to number steps if more than one step is required for the complete transformation. If any product forms as a stereoisomeric mixture, then draw only one clearly showing valid stereochemistry and write " enantiomer" or " diastereomer" or " stereoisomers" (when more than two stereoisomeric molecules can be drawn). (ii) (i) C 2 6 a excess 2 (excess) Pd/C - if add " anything" when it does not apply Draw ALL products; place each in the appropriate box based on its predicted MR signals. 2 C-MR signals C-MR signal ) (excess) 2) Zn (i) C 6 0 (ii) ) 2/PdBaS/quinoline 2) any peroxyacid C 6 2 single product D. (i) C 9 7 this pi bond can also be used with same results one equivalent must be D either one of these note: either pi bond is identical and must write enantiomer ( pt) no pts for relationship if drawing is not correct (ii) The reaction shown directly above also yields product shown below (a structural isomer of the products you have drawn above). Ignoring stereochemistry, draw a complete curved arrow mechanism for the formation of this product. ote: there is no indication of any carbocation formation. either pi bond can be used return arrow can go to either C of the pi bond pts intermediate (all or nothing with charge) Product points for each mechanism - no partial, all arrows 9
III. (25 points) ame Page In this set of reaction predictions, it has already been determined that two different organic products form (please ignore byproducts). This time, please 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. nly one product is optically active either product is optically active o credit for this part unless ) B 2 6 2) 2 2 /a nly one product is optically active either product is optically active o credit for this part unless 2 / nly one product is optically active either product is optically active o credit for this part unless D. E. KMn as S S nly one product is optically active either product is optically active o credit for this part unless nly one product is optically active either product is optically active o credit for this part unless
IV. (28 points) ame Page Each reaction starting with Molecule shown below leads to a product set containing only two compounds sharing the same molecular formula (please IGRE other byproducts); draw these products and define their relationship. C 2 Li S ac C relationship of products relationship of products structural isomers C or constitutional diastereomers 5 pt pt 5 When Compound is heated in ethanol, solvolysis encourages rearrangement and a mixture of E products results. ne of these products,, is shown at right. Its formation is predicted by the formation of a resonance stabilized carbocation intermediate. S C 2 prolonged heating C 2 2 and other products (a) Draw the most straightforward curved-arrow mechanism for formation of from. C 2 S pts each intermediate pts each mechanistic step grading stops with first irrational step 5 (b) Draw the other elimination product expected to form after a single favorable carbocation rearrangement with resonance stabilization as above; it is an isomer of above.
V. (5 points) ame Page 5 These next reactions are more complicated either because more than one mechanistic path is predicted to occur or because the mechanistic path can lead in several different directions. The result is a more complex product set. Provide the requested drawings using the information given. Elimination and substitution occurs under these harsh conditions. Li (i) elimination product(s) C 6 8 (ii) substitution product(s) C 7 excess -2 for missing any product or drawing impossible products Provide the complete IUPAC name (including stereochemistry as needed) for the starting material above. (R,Z)-,5-dichloro--methylpent--ene all or nothing - 2pts each error (numbering, order, etc) root must be correct Uncharged elimination and substitution products result from these mild conditions, too, as nitrogen gas is evolved. (i) elimination product(s) (ii) substitution product(s) -2 for missing any product or drawing impossible products Use the molecular formulae to guide you, provide missing products/starting materials and reagents (be sure to number your steps if more than one chemical transformation is required). LiC 2 C 2 C 2 2 one equivalent C 7 9 Li C 5 8 Li 2 pts each, must have stereo. B 2. 2 2 /a. or Ts/pyridine and then a Li C 7 0 2 (E) C 2