Page 1 EXAM TWO CHEMISTRY 0310 PROF WILCOX NOVEMBER 1 2012 NAME PeopleSoft 1 Write your name or initials on the second page of the exam 2 Read all questions carefully There are 9 questions and there are 7 pages to this exam Check to be sure that you have all pages 4 Check the blackboard at the front from time to time to see any late bulletins about the exam Please stay in your seat Raise your hand if you have a question Ask for help if you feel there is an error in the exam or if a question is unclear 5 A key will be posted asap on Courseweb 1 24 2 6 3 24 4 6 5 5 6 14 7 6 8 6 9 9 TOTAL 100 Page 2 Page 3 1 Predict the major product of each of the following reactions Circle whether the reaction proceeds by the SN1 SN2 E1 or E2 pathway Br CH3 3CO Na SN1 SN2 E1 E2 Br Na NH2 CH3CH2O Na OCH2CH3 Br CH3 CH3OH H3CO CH3 O HOCCH3 O O Na SH SH Br Cl I SN1 SN2 E1 E2 SN1 SN2 E1 E2 SN1 SN2 E1 E2 E1 also circled OK SN1 SN2 E1 E2 E1 also circled OK SN1 SN2 E1 E2 2 Give the two major substitution products of the following reaction HOCH2CH3 H3C H Br H C6H5 C6H5 OCH2CH3 C6H5 H3C C6H5 H3CH2CO H3C H H H H C6H5 C6H5 any manner of showing retention and inversion substitution products is OK a b c d e f 3 Complete the following reactions In a the aqueous workup steps have been omitted Page 4 LiAlH4 O O OSO2CH3 KCN NaCN etc CN OH OH CN Br LiAlH4 OH O PCC or Na2Cr2O7 or H2CrO4 Na2Cr2O7 or H2CrO4 OH O H3C excess conc H I H3C OH O I I a b c d e f 4 Provide reagents for the following two transformations If a transformation requires more than one step number the reagents for the steps sequentially Br 1 Li or Mg O 2 H3C H 3 H2O or H H2O Br2 light H3C OH Page 5 5 Circle true or false a Thiols have higher boiling points than alcohols True False b H20 is a better leaving group than bromide Br True False c Carbocations are strong Bronsted acids True False d H2S is a better nucleophile and H2Se True False e OCH3 is a stronger base than SeCH3 True False 6 a Provide a synthesis of 2 methyl 3 hexanol from 1 bromobutane You may use any other organic reagents containing 3 carbons or less and our usual inorganic reagents and chemicals synthesis OH Br NaOH PCC OH O MgBr or chloride or isopropyllithium showing preparation of the organometallic is not required b Provide a synthesis of t butylpropyl ether from 2 propanol Same rules as above OH synthesis O PCC or Na2Cr2O7 H2SO4 CH3Li or CH3MgX O OH OH Page 6 7 Provide a correct mechanism for the following reaction Show how both products form Include all steps Show protonation and deprotonation steps O HOCCF3 H2O O OH H O H O H H ROH showing ROH not required 8 Use a Newman projection to illustrate the transition state for the following reaction and circle the major product one of the two possibilities shown H CH3 CH3O Br CH3 CH3 CH3 CH3 CH3 OK to omit arrows and base Br H CH3 CH3 CH3O Page 7 9 Explain briefly but clearly why polar solvents accelerate the SN1 reaction Illustrate the complete mechanism of the reaction provide a correct reaction coordinate free energy diagram and explain why the polar solvent can make the activation energy lower Relative rate CH3 Br CH3 OH HBr 400 000 100 H2O 90 acetone 10 H2O CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 Br CH3 OH HBr 1 c Explanation of rate effect Polar solvent stabilizes charge The transition state is developing charge Polar solvent therefore lowers the transition state energy and has less effect on A the starting material