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HO Cl CH3 Br H3C HO C O O S CH3O O CH3 O CH3OH 1. Use appropriate curved arrows to indicate the complete mechanism of each of these reactions. a) b) + HBr + KCl c) 2. A pure chiral compound has a specific rotation of +100°. Determine the % composition of an enantiomeric mixture 3. Draw the appropriate structure in each empty box based on the compound(s) and type of arrow provided. .. .. .. .. . a . ) b) + + c) + KH (1 equiv.) CH3OH OCH3 Br2 H2O H3C Br HO While writing the mechanism, justify both the regiochemistry and the relative stereochemistry shown here. Make sure that you understand these terms. + enantiomer + HBr - N :C C CH3 a+ .. .. H .. .. - ether of this compound that has a specific rotation of + 60°. S CH3 O O .. .. .. + NaOTs - THF 4. a) Draw the mirror image of this molecule in the box to the right. OH OH b) Is the above molecule chiral or is it a meso compound? 5. Assign the stereochemistry in each of the following molecules, using the Cahn-Ingold-Prelog i) ii) iii) a) b) OH H3C CH2CH3 H i) ii) iii) Cl H3C CH3 H H Cl 2CH CCl 3 CH2Br CHBr2 c) 6. In the blanks below the molecules label each molecule as 'chiral' or 'achiral'. CH3 CH3 Br Cl CH3 CH3 CH3 7. Which of the following pairs of carbon atoms in this molecule are not chemically equivalent E a) A & D b) A & E c) B & C d) F & H e) none of the above G (i.e., all are equivalent) to one another? A B C D F H priority rules. In each blank, indicate either, 'R', 'S', 'E', 'Z', or 'N/A' (for 'not-applicable', when a particular atom is nonstereogenic). 8. Which of the following carbocations is not resonance stabilized? a) b) c) + d) O H + CH2 + H3C CH3 + .. .. + e) H3C CH3 CH3 NH2 HO d) H NH2 HO O e) O O CH3 O O H Me Me H Cl Cl Et Et Et Me Me Me Me Et Et Et Et Et Cl Cl 9. Which of the following pairs of molecules are not constitutional isomers of one another? and and and a) b) d) c) none of the above f) all of the above and and and and a) b) c) d) 10. Which of the following pairs of molecules are cis/trans stereoisomers of one another (i.e., not a and e) CH(CH3)2 Cl CH(CH3)2 Cl 12. How does the difference in stereochemistry between these two starting materials affect the type of 11. Draw the full mechanism for the formation of the product shown here. CH3 C C CH3 KH DMSO pair that are simply drawn differently nor constitutionally isomeric)? H+ (cat.) KH DMSO products formed from this reaction. Draw the major elimination product expected in each case and explain why it is the major one. CH3 H OH H3C H3C H3C CH3 CH3 + H2O H3C NH (A) DMF I C II (B) OCH2CH3 H3C C C C C C CH3 CH2Cl H H H H3C Cl (C) 16. Draw each of the following stereoisomers in its most stable chair conformation. Then indicate cis-1,3-diethylcyclohexane trans-1,3-diethylcyclohexane c) 14. Provide the IUPAC name for each of the following molecules, designating stereochemistry where 17. Shown below are three contributing resonance structures for the conjugate acid of ii) Calculate the formal charges on all of the nitrogen atoms within each of the resonance i) Draw curved arrows, above, to indicate how you would "push" electrons in structures (A) and (B) KOtBu 13. The following reaction occurs via an E2 mechanism, in which an alkene (II) is formed via a βelimination reaction of the bromine in I. The stereochemistry of the product is not shown, but one alkene stereoisomer does predominate in this reaction. a) Draw a Newman projection (or a comparable drawing which clearly indicates conformation) of the reactive conformation of I. b) Using the information from (a), determine the stereoisomer of the alkene (II) that results from this reaction and draw it in the box below. whether the cis or trans isomer is lower in energy? Explain why. appropriate using the R/S and E/Z conventions. Ph CH3 H Br H OCH2CH3 Ph CHCH3 15. Draw the following molecules: a) (Z)-6-ethyl-2-decen-4-yne b) (2R,4R)-4-methyl-2-octanol C NH2 NH2 .. .. H3C NH C NH2 NH2 .. .. H3C NH C NH2 NH2 .. N-methylguanidine. and thus convert each to the structure on its right. structures (A, B, and C). Write your answers beside the appropriate atoms, above. .. c) trans-2-methoxycyclohexanol (Note that this molecule is chiral, but only the relative stereochemistry is specified; thus, you may draw either enantiomer). + + + Br Cl b) a) F H2O H2C CH2 HC CH CH3OH H3C CH3 O NH3 HC OH CH3CH2NH2 a) b) c) 18. Circle the molecule with the lowest pKa (i.e., strongest acid) in each of the following horizontal rows. 20. Clearly explain why it would be impossible to prepare this compound via a Williamson ether synthesis. (a) (b) O C CH3 CH3 CH3 Then suggest a way that you could synthesize it (from phenol and what else?) 19. Show how you would synthesize each product from the starting material provided. Each H3C CH3 H3C C C CH3 synthesis takes at least two steps. Draw all isolable intermediates. Cl d) CH3 CH3NH2 SH CH3OCH3 CH3OH H Br H Cl H I H F 21. When this reaction is performed in aqueous solution at 25°C, ΔH = -0.12 and TΔS = -0.27 CH3CH2COH O CH3CH2O- O + CH3CH2COO CH3COH O + propanoic acid acetate anion propanoate anion acetic acid Baed on the above information, what can you infer to be true? a) This reaction favors the formation of the products (propanoate anion and acetic acid) at 25°C. b) This reaction is endothermic. c) Raising the termperature of this reaction will favor the formation of more propanoate anion and acetic acid. d) The starting materials disrupt the order of hydrogen bonding in the solvent (i.e., water) more than the products do. 22. Estimate ΔH for the following reaction (bond dissociation energy values are provided). CH3OH + H2C CH2 H3C CH2OCH3 Bond Dissociation Energies H OCH3 HO R H CH2CH3 104 kcal/mol 92 kcal/mol 100 kcal/mol a) +362 kcal./mol b) + 46.0 kcal/mol c) -22 kcal/mol e) -362 kcal./mol d) -30 kcal/mol H2C CH2 (π-bond only) 66 kcal/mol

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