Chem 348 Final Exam Name _______________________Thursday May 6, 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. 16 points possible Acid Benzyl oxonium cation pKa <0 Propyl propionate pKa ~20 Pentane‐2,4‐dione pKa ~20 Allyl amine pKa 35 Conjugate Base NH name: benxyl alcohol name: Propyl propionate enolate anion name:pentane‐2,4‐dione anion name: allyl amide anion 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. 16 points possible Base 3‐Pentoxide anion Methanide anion p‐Ethoxyanilinium cation Cyclopentadienyl anion Conjugate Acid pKa ~15 pKa ~60 CH4 pKa 5 pKa 15 name:3‐pentanol name: methane name: p‐ethoxyaniline name: cyclopentadiene 3) Consider the diketone hexane‐2,5‐dione, which under acidic conditions and high heat is converted to 2,5‐dimethylfuran. Devise a reasonable mechanism that accounts for this transformation using the curved arrow notation to account for all bond making and bond breaking. Remember this reaction is run under acidic condition so do not show any negatively charged species in your mechanism . 10 points possible OOO2,5-dimethylfuranhexane-2,5-dioneH+12345OH67OH32O65417OH232O65417OH32O65417HHOHH 4) Benzaldehyde reacts with a 50 % solution of aqueous sodium hydroxide to give a 1:1 mixture of two products ‐ benzyl alcohol and benzoate ‐ in the Cannizzaro Reaction, a reaction you have not seen before but have the tools to rationalize. When deuterium is used for labeling, the following is observed: Devise a reasonable mechanism that accounts for this reaction using the curved arrow notation to account for all bond making and bond breaking. 10 points possible 5) Complete the following: Stereochemistry and regiochemistry are important. 30 points possible a)b)c)d)f)g)h)i)typetypetypetypetypetypetypetypetypej)typee)CO2Me40oCa),remove H2Ob) PCC, CH2Cl2THF (aq)CF3CO2HOOONaOH,NOOa)b) H3O+OOOPh3P=CHCHOOOb)c) NaOH, H3O+,Malonic Ester SynthesisOOHa) DMSO, (COCl)2CH2Cl2,-20oCb) Et3N, -20oCa) (COCl)2,cat.DMFCH2Cl2OOHOBr2,HOAca)CO2HOEAS - AlkylationCHOOOHOHCH2OHCO2MeOCHOWittingDiels-Alderacetal formation; oxdationO OMichael w/ enamineOBralpha brominationEtOOEtOONaOet/EtOHBrBrOCHOSwern oxidationOClOformationofacidchlorideOOOOHOOOOOOOOORobinson (Michael then aldol)for i) above 6) Use molecular orbital analysis (sketch the HOMO/LUMO pi interactions) used to predict the Diels Alder reaction to predict if allyl anion OR allyl cation could react with ethylene in a thermal cycloaddition reaction. 8 points possible HOMOLUMOLUMOHOMOLUMOHOMOallyl anionallyl cationethylenefavorable interactions w/ allyl anion LUMO andethylene HOMO = orbital matchedbondingbonding7) Propose a synthesis of the following molecule starting from 4‐(3‐bromopropyl)benzaldeh y de. Use any reagents and starting materials necessary to accomplish this transformation . 10 points possible