CH204_F15_X1_Pract_AnsMontgomery College – Takoma Park – Silver Spring Campus Chemical & Biological Sciences Division CHEM204 – Organic Chemistry II Fall 2015 Practice Exam 1 Answers C. B. both having formula C9H17Br.LiAlH4 2. Treatment of a hydrocarbon A (C9H18) with Br2 in the presence of light forms alkyl halides B and C. and D. Reaction of either B or C with KOC(CH3)3 forms compound D (C9H16) as the major product. Ozonolysis of D forms the fragments shown below. O A O B C D Br Br 2. Identify A. H3O+. ∆ G (major) G H (minor) + H . Propose a structure for each lettered compound O F O E E F O O O 1.CH204_F15_X1_Pract_Ans Problem 1 1. CH204_F15_X1_Pract_Ans Problem 2 Propose a structure for the lettered compounds. KOC(CH3)3 NBS I M (C6H10) J NBS K PCC NaOH hν Q O+Q N P O K P I J K M Q P Br N O Br HO O . CH3Cl 6 1. 1 O O PCC CH2Cl2 O HO 2 O KMnO4 CHO O O OH H3O+ O OH 3 Na2Cr2O7 Br H3 O No Reaction + 4 Na2Cr2O7 O O H2SO4 (aq) O O O OH 5 1. mCPBA 2.CH204_F15_X1_Pract_Ans Problem 3 Complete the following reactions by giving the major organic product(s). NaH O O 2. CH3Br OH O . LiAlH4 O 3. Write NR if no reaction occurs. H 2 O 8 OH O Cl O O OH O O 9 D DBr D Br Br 10 O O O O O O O O 11 O O O O No Reaction 12 O O O O . LiAlH 4 Cl O H 2.CH204_F15_X1_Pract_Ans 7 1. 2-product. it yields compound S (C5H6). Proton NMR of R shows two singlets with a 2 to 1 relative area. When Q is dehydrated. T and U. T is the 1. Q (C5H10O2) reacts rapidly with KMnO4 under acidic conditions to give compound R(C5H6O2) as the sole product. Deduce the structures of Q.CH204_F15_X1_Pract_Ans Problem 4 A symmetrical cyclic compound. two isomeric products were isolated. Q R HO OH S O T U D O Br D Br Problem 5 Circle the aromatic compounds O O S O O N N H B O N O . R. Compound Q does not react with H2 over a platinum catalyst. S. T and U. When S is reacted to one equivalent molar of DBr. 3-Epoxy-2-methylbutane is reacted with LiAlH4/H2O followed by treatment with acid and heat.CH204_F15_X1_Pract_Ans Problem 6 Draw a stepwise mechanism for each of the following reactions: (a) 2.3-cyclohexadiene is reacted with 1 eq. O O H H H OH H H O O O H Al H H H H H - H + O + H H H H H H H OH (b) 1. D + Br D D + (2) (1) (1) + - D (2) Br Br D D D - + Br Br . DBr. Br Br . . Or Br Br Br (1) The other products are obtaiνed by the same mechaνism for the other iνtermediates Br Br (2) Br Br (3) (4) (5) Br (6) (7) . Br . Br H . O O Hb NBS Ha hν NBS = N N.CH204_F15_X1_Pract_Ans (c) 1-methyl-1. (6) (5) (7) Last Step (two possible paths) for Iνtermediate (1) .3-cyclopentadiene is reacted with NBS and light. H . . . Br hν O O Attackiνg Ha Br . (2) (1) (3) Attackiνg Hb H . . (4) . . CH204_F15_X1_Pract_Ans Problem 7 Label each compound as aromatic or not. Assume all completely conjugated rings are planar. The lone pairs are not shown. (a) (b) (c) O (d) S S O N Aromatic Aromatic (e) (f) (g) (h) O O + B Aromatic Aromatic (i) Aromatic (j) (k) (l) O . OH J(C6H8O2) I (C6H10) H2 K(C12H18O 2) Pt OH I J K O O O O . F(C6H10O) G(C7H12O) H(C13H22O 2) O 1. 1. LiAlH4 2. H3O+ OH F G H O O O O 2.CH204_F15_X1_Pract_Ans Problem 8 Propose a structure for each lettered compound. 1 HO NO 2 O 2N NO 2 HNO3 H2SO4 HO NO 2 + OH 2 OH SO3 SO 3H H2SO4 3 Br2 Br FeBr3 O O 4 Cl AlCl3 5 OH KMnO4 H3O+ O O OH 6 Cl Cl Br2 Br hν HO NO 2 .CH204_F15_X1_Pract_Ans Problem 9 Complete the following reactions by giving the major organic product(s). Write NR if no reaction occurs. CH204_F15_X1_Pract_Ans 7 1. H3O+ O O O HO O OH O O . HCl NO 2 9 Br Br 1. Fe. Zn(Hg). KMnO4. CH3Cl / AlCl3 NH2 2. LiAlH4 3. HCl O 2. ∆ Cl O 10 NO 2 O O HNO3 Cl H2SO4 Cl O 11 O O CH3COCl O O + O AlCl3 O O 12 1. Cl2/FeCl3 Cl Cl Cl 8 1. Cl2 / AlCl3 2. H3O+. N2H4. OH- O 2. ) The ortho/para attacks leads to very unstable intermediates (circled in red) favoring thus the meta attack. . HNO3 H2SO4 O Show all resonance forms Electrophile formation (1 points) + HNO3 O S OH O O H HSO 4 - + H2NO 3 + NO 2 + + H2O Ortho Attack (2 points) NO 2 O O O H NO 2 + O O NO 2 NO 2 H + NO 2 H H + + H NO 2 H2O + Meta Attack (2 points) O O O O + + H NO 2 NO 2 + + NO 2 NO 2 H H H + O H2O H NO 2 Para Attack (2 points) O O H O O O + NO 2 + + H NO 2 + + H NO 2 H NO 2 O 2N H2O H Explain why the meta product is the major product (2 points. 1.CH204_F15_X1_Pract_Ans Problem 10 Draw a stepwise mechanism for each of the following reactions and draw the structure of the major product(s). . AlCl3 + HO Cl Show all resonance forms Electrophile formation (1 points) Cl AlCl3 Cl Cl + Al - Cl + + Cl Ortho Attack (2 points) OH O OH H + + OH H H + OH OH + H H2O + H H + Meta Attack (2 points) OH OH OH OH H OH + + + H2O H + H H H + Para Attack (2 points) H OH OH O OH H + OH OH OH + + + H + H H H + H2O H Explain why the ortho/para product is the major product (2 points.CH204_F15_X1_Pract_Ans 2.) The ortho/para attacks lead to 4 resonance forms where one respects the octet rule while the meta attack leads to only 3 forms none of which respects the octet rule.