CHEM 346 EXAM 1 ANSWER KEY February 21 2012 Name Instructions This is a one hour exam which you will have two hours to complete You are only allowed to use molecular model kits scratch paper and your brain Good luck Chem 346 Exam 1 2012 16 15 24 Question 3 Question 4 Question 2 Question 1 The following list of reagents may be of use to you for this exam Question 5 Question 7 Question 6 TOTAL 10 13 12 10 100 AlCl3 Br2 Cl2 Cu I CuBr CuCl CuCN Et3N FeBr3 FeCl3 H2 HBF4 HCl H2NNH2 HNO3 H2O H3PO2 H2SO4 KI KMnO4 Mg0 MnO2 Na2Cr2O7 NaCN NaNH2 NaNO2 NaOCH3 NaOH Pd C Pd PPh3 4 P2O5 Pt C Sn0 SOCl2 Zn Hg h Chem 346 Exam 1 2012 1 Describe each of the following transformations as an oxidation reduction or neither and explain your designation based on labeling the oxidation levels of the carbons involved in the transformation 3 points each A I Reaction classification reduction B 2 O 2 0 Reaction classification neither C O OH 0 1 H3C Reaction classification oxidation D OH 2 O 1 Reaction classification reduction E Cl O 3 HO 1 CH3OH Reaction classification neither I 0 0 2 Br Br O OH 0 OH 2 H3C OH 1 OH 1 1 H3CO 3 Cl 1 H3CO H3CO 1 Chem 346 Exam 1 2012 2 Predict the product s of the following transformations 8 points each A 1 SOCl2 2 H3CO AlCl3 3 KMnO4 O OH O OH H3CO O B C F O OH 1 HNO3 cat H2SO4 2 CH3CH2OH cat H 3 Cl2 FeCl3 Cl O OCH2CH3 1 acid chloride formation 2 FC acylation ortho to strongly activating group 3 oxidation of benzylic position NO2 1 nitration meta selective 2 Fisher esterification 3 chlorination meta selective NO2 1 Br2 FeBr3 2 NaOCH3 3 Pd C H2 Br NH2 H3CO 1 bromination ortho to fluorine meta to nitro 2 nucleophilic aromatic sub 3 reduction of nitro to amine Chem 346 Exam 1 2012 3 Provide reagents conditions for executing the following synthetic sequence You may assume that you can separate ortho and para isomers Each arrow should have one set of reaction conditions this doesn t include workups 8 points each A OH O SOCl2 NH3 Et3N P2O5 Cl2 FeCl3 Cl CN B Br2 h NaCN O O H2O H Cl AlCl3 O O Chem 346 Exam 1 2012 4 The following reaction was conducted and two products of electrophilic aromatic substitution were observed Based upon your knowledge of brominations show the two products that were formed with a clear explanation of the selectivity of these two molecules over all other potential EAS products 10 points Br Br2 OMe OMe Br OMe The question requires an analysis of the two groups to determine which may be the better at ortho para directing In this case one could also look at the conditions Br2 no FeBr3 to note that the group must be strongly activativing which likely implicates the influence of the ether OMe OMe OMe H Br H Br Br Br H Br O Me H Br OMe H Br OMe The methoxy alkene group through resonance forms provides additional stabilization Br Br Br H OMe OMe same resonance effects here Br Br Br H OMe OMe OMe Br H Br H OMe Can never use ether group to stabilize this cation Same effect when substituting at the other position Chem 346 Exam 1 2012 5 Provide a synthesis of compound A from benzene B using reagents and conditions that we have discussed in lecture You may assume that you can separate ortho and para isomers 12 points F from NO2 A NO2 Sn HCl HNO3 H2SO4 HBF4 F Cl AlCl3 B NH2 NaNO2 HCl F HNO3 H2SO4 N2 Cl F NO2 Chem 346 Exam 1 2012 6 Provide an arrow pushing mechanism for the following transformation Writing proton transfer for the applicable processes is ok 13 points HO OH O O O O O O O O O O O OH HO O O H O O O O O O HO HO O O O OH HO O BH HO O O O H O O B O O O O writing proton transfer ok proton transfer O O H O O O O O O O O H O O O O O O O O OH Chem 346 Exam 1 2012 7 In class we discussed the use of thionyl chloride SOCl2 to convert carboxylic acids to acid chlorides Another reagent that is capable of this same transformation is oxalyl chloride COCl 2 drawn below Based upon your knowledge of the thionyl chloride reaction provide an arrow pushing mechanism for the reaction below illustrating the effectiveness of this reagent for enabling this transformation Writing proton transfer for the applicable processes is ok Hint think about the byproducts 10 points O OH O Cl Cl O oxalyl chloride O Cl byproducts With SOCl2 the reaction involves a mixed anhydride where chloride replaces the anhydride and the leaving group irreversibly collapses to SO2 and chloride The question here is what the comparative leaving group is and how does it irreversibly convert to something else O Cl O O Cl OH H O O O Cl Cl O O O Cl Cl O H O Cl HCl H O O O O Cl O O O H Cl O Cl O O O Cl O O O Cl O byproduct leaving group H O Cl H O Cl O C O CO2 C O C O Cl CO carbon monoxide The byproducts of carbon monoxide and carbon dioxide irreversibly form leaving chloride as the lone counterion Just like with SOCl2