Chem 348 Hourly Exam 2 Name _______________________Wednesday March 31, 2010 Student #_____________________1) Consider the reaction AH(+) + H2O → A:( ‐) + H3O(+). For the following named acids: a) draw the structure of the acid, b) give the approximate pKa of the acid, c) give the name of the conjugate base, and d) draw the structure of the conjugate base. Acid iso‐Butyl alcohol pKa Cyclopentadiene pKa Ethylbutanoate pKa Diisopropyl amine pKa Conjugate Base name: name: name: name: 2) Consider the reaction B:(‐) + H3O+ → BH(+) + H2O. For the following named bases: a) draw the structure of the base, b) draw the structure of the conjugate acid, c) give the approximate pKa of the conjugate acid, and d) give the name of the conjugate acid Base t‐Butyl acetate enolate anion Imidazole p‐Toluenesulfonate anion Phenoxide anion Conjugate Acid pKa pKa pKa pKa name: name: name: name: 3) The barrier to rotation for compound 1 about the indicated C‐C bond is about 65 kcal/mol. Compound 2 (called calicene) has not been synthesized, but computational methods agree the inter‐ring rotation should be about 32 kcal/mol. Using good molecular orbital arguments, explain using words and pictures why calicene (2) has much lower predicted barrier to r otation about the indicated C‐C bond. 4) When 2‐cyclobutylpropan‐2‐ol is treated with a solution of HBr in Et2O, 2‐bromo‐1,1‐dimethylcyclopentane is the resulting product. Write the reaction and propose a mechanism using curved arrows notation in each step. 5) Complete the following: Stereochemistry and regiochemistry are important. a)b)c)d)f)g)h)i)typetypetypetypetypetypetypetypetypej)typee)CO2Me40oCOHPBr3PhOOH2,Pd/CEtOHhydrogenolysisNBS, hCCl4CHONH2a) NaNO2/H2SO4(aq)b) CuCNPhOsO4,NaIO4THF (aq)FNO2O2NH2NCO2Menucleophilic aromatic substitutionHBrperoxidesClPhOHSiPhPht-BuHOimidazole, DMF+ 6) Propose a synthesis of (E)‐5‐heptene‐2‐ol using precursors that contain fewer than four (< 4) carbon atoms. Use any necessary organic or inorganic reagents; any reagents or precursors used may contain more than four carbon atoms if fewer than four of the carbon atoms from that reagent or precursor remain in your final product. 7) (S)‐1‐phenyl‐4,5‐dihydroxypentan‐1 ‐one can be converted into (1S, 4S)‐1‐phenyl‐2,7‐dioxabicyclo[2.2.1]heptane in one simple step. Write the reactio n and propose a mechanism using curved arrows notation. I pledge on my honor that this exam was completed by me, that I received no unauthorized help, and that I have not violated the honor code of the University. Please sign your name