CHEMISTRY 104 Hour Exam I Summer 2009 Page 1 Answer the following ten questions (1-10) true (A) or false (B) (1 point each). Capsaicin is the active compound in chili peppers. A partial Lewis structure for capsaicin is: O H k CH 3 g CH3 j C CH2 CH2 CH 2 CH2 CH 2 CH CH N O l CH i CH 3 h H H H O H Complete the Lewis structure and answer the next seven questions. 1. Of all the indicated bond angles (g-1), bond angle j is the largest. 2. There are more atoms with sp2 hybridization than atoms with sp3 hybridization. 3. The bond angles marked g, i and k are all approximately 120o. 4. The nitrogen atom is sp2 hybridized. 5. Capsaicin is more soluble in an aqueous acidic solution than in pure water. 6. There are 4 lone pairs of electrons in the completed Lewis structure. 7. The bonds in capsaicin are all formed from overlap of unhybridized p atomic orbitals. ----------------------------------------8. The stability of aromatic hydrocarbons is primarily due to the delocalized electrons found in benzene. 9. Addition polymerization can be initiated by using a peroxide, e.g., benzoyl peroxide. 10. Alkynes can exhibit cis/trans isomerism. CHEMISTRY 104 Hour Exam I Summer 2009 Page 2 MULTIPLE CHOICE (3 points each) 11. The skeleton structure of TCNQ, C10N4O2, is given below. Complete the Lewis structure and answer the next question. O N C C C C N C C N C N C C C O How many bonds are in the completed Lewis structure? a) 6 12. b) 8 c) 10 d) 12 e) 13 How many of the following compounds have free rotation about every bond in the molecule? I. cyclopropane II. ethane IV. ethyne V. benzene a) 1 b) 2 c) 3 III. ethene d) 4 e) 5; All have free rotation about every bond. 13. In class, the TA named a molecule 2-ethyl-4-tert-butylpentane. An alert student pointed out that although the correct structure could be drawn, the name did not follow IUPAC rules. What is the correct IUPAC name for the molecule? a) 5-methyl-2-tert-butylhexane b) 2-ethyl-4,5,5-trimethylhexane c) 3,5,6,6-tetramethylheptane d) 2,2,3,5-tetramethylheptane e) 3-methyl-4-tert-butylhexane CHEMISTRY 104 Hour Exam I 14. Summer 2009 Page 3 Name the following compound: CH3 H a) trans-5-ethyl-5-methyl-2-octene CH3 C CH 3 CH 2 CH 2 C C CH2 b) trans-4 -ethyl-1,4-dimethyl-1-heptene H CH2 c) cis-3-methyl-3-propyl-6-hexene d) trans-4-ethyl-4-methyl-6-octene CH3 15. How many different monochlorination products are formed in the reaction shown below? CH 3 CH 3 CH CH CH 3 light + Cl2 CH 3 a) 1 16. b) 2 c) 3 d) 4 e) 5 How many of the following four types of hydrocarbons undergo addition reactions easily? I. alkanes a) 0; None II. alkenes b) 1 c) 2 III. alkynes d) 3 e) 4; All easily undergo addition reactions. IV. aromatics CHEMISTRY 104 Hour Exam I 17. Summer 2009 Page 4 Which of the following statements about cyclohexane is false? a) Its molecular formula is C6H12. b) The chair conformation is more stable than the boat conformation. c) It is a planar molecule. d) All bond angles are about 109o. e) It is a structural isomer of 2-hexene. 18. Choose the correct order of reactants, intermediates and products for the acid catalyzed hydration of the following alkene. first last a) II, III, IV, I b) II, I, IV, III c) II, IV, III, I d) III, I, e) II, + H+/H2O CH3 IV, II IV, I, III H H O H I. II. + H+ CH 3 CH 3 HO H IV. III. + CH 3 H+ + H 2O CH3 CHEMISTRY 104 Hour Exam I Summer 2009 Page 5 For the next two questions, refer to the compounds in Question 19. 19. Which of the following compounds (I-VI) exhibit cis-trans isomerism? Pair X: CH 3 CH 3 CH 3 II I Pair Y: CH 2 CHCH2 CH 2CH 3 CH 3CH III C 2H 5 CHCH2 CH 3 IV Pair Z: O CH 2 CH O CH 2 CH3 V VI a) I, II, III, IV 20. b) I, II, IV d) pairs X and Z ----------------- e) II and IV only b) pairs X and Y c) pairs Y and Z e) pairs X, Y and Z Consider the combustion reaction of 2-propynal. What is the coefficient in front of O2 in the balanced combustion reaction assuming one mol of 2-propynal reacted? a) 4.5 22. d) III, IV, V In which of the pairs (X, Y, and Z) is/are the compounds structural isomers of each other? a) pair Y only 21. c) all of them b) 4 c) 3.5 d) 3 e) 2.5 Which of the following compounds (a-d) cannot hydrogen bond with itself? a) methyl amine b) 2-pentanone c) phenol e) All the compounds (a-d) can H-bond with itself. d) benzoic acid CHEMISTRY 104 Hour Exam I 23. Summer 2009 Page 6 Which of the following compounds will have the lowest boiling point? CH 3 b) a) CH 3CH2 CH 2 CH 2CH 3 CH 3 C c) CH 3 O CH 3CH2 CH 2 CH CH 3 O d) e) CH 3CH2 CH 2 CH 2CH 2CH3 CH 3CH2 CCH 3 24. The following molecule contains which functional groups? O C H N C CH2 C C C CH C H 2N OCH 3 H a) b) c) d) e) 25. O alcohol, aldehyde, amine, ketone aldehyde, amide, amine, ether amide, amine, ether, ketone amine, ester, ether, ketone aldehyde, amine, ether, ketone An unknown organic compound is isolated. The unknown compound can be oxidized to a ketone but it does not decolorize a brown bromine (Br2) solution. Which of the following (a-d) is a possible structure for the unknown compound? CH 2 CH O OH CH 3CH2 CH2 C H b) a) OH O C c) OH d) CH3 CCH2 CH2 CH 3 CH 2CH 3 e) None of the above could be the unknown organic compound. CHEMISTRY 104 Hour Exam I 26. Summer 2009 Page 7 Which of the following typifies the amino acid linkage in proteins? a) c) b) R C R R O 27. R O R O C N O H R R large molecular weight, branched chains, syndiotactic large molecular weight, linear chains, atactic large molecular weight, linear chains, isotactic small molecular weight, branched chains. syndiotactic small molecular weight, linear chains, atactic You are asked to create a synthetic fiber for use in mountain-climbing robes. Which functional group, when incorporated into the fiber at position X, will product the strongest rope? X a) ether X b) ketone X X c) chloride n d) alcohol e) aldehyde ----------------------------------------29. Estradiol is a female hormone with the following structure. What is the molecular formula of estradiol? H 3C OH a) b) c) d) e) C18H24O2 C17H22O2 C18H28O2 C17H20O2 C18H20O2 HO 30. O You are asked to find a new polymeric material for a proposed space station. It must have high tensile strength. Which properties would you look for in the polymer? a) b) c) d) e) 28. C d) How many chiral carbons does estradiol (the compound in question 29) have? a) 1 b) 2 c) 3 ----------------------------------------- d) 4 e) 5 R CHEMISTRY 104 Hour Exam I Summer 2009 Page 8 FREE RESPONSE QUESTIONS – Points as indicated. 31. The amino acid ValineH+ has the following structure with pK a1 = 2.3 and pK a 2 = 9.7. CH 3 15 pts. H H HC CH 3 N C C H H O O H a) What is the R group that differentiates valine from the other approximately 20 amino acids present in the body? b) Most amino acids are optically active. In the structure above, place a box around the optically active atom(s) [the chiral atom(s)]. c) Consider the titration of 50.0 mL of 0.10 M ValineH+ with 0.10 M NaOH. Sketch the titration curve (pH vs. volume of NaOH added). On your sketch, show the pH of the solution at 25.0 mL, 50.0 mL and 75.0 mL of NaOH added. CHEMISTRY 104 Hour Exam I Summer 2009 Page 9 d) Valine has the three different charged forms (shown below) depending on the pH of the solution. Each dominates (is the only major amino acid species present) at specific volumes of NaOH added. At what volume of NaOH added does each form dominate? CH 3 CH 3 CH H 2N CH CH 3 COO Volume NaOH added = CH 3 CH Volume NaOH added = H 3N CH CH 3 COOH CH 3 Volume NaOH added = CH H3N CH COO e) Circle the form(s) above which is/are the major amino acid species present at the isoelectric point. CHEMISTRY 104 Hour Exam I 32. Summer 2009 Page 10 Name and write the structural formula for the major organic product in each of the following chemical reactions. 12 pts. O H+ a) CH 3OH + HOCCH 2CH3 b) C 6 H6 Cl2 FeCl3 O 33. 6 pts. O LiAlH4 (excess) c) H d) HC C CH 2 C CH C CH3 CH2 HBr (excess) When HCl is reacted with 1-methyl-1-cyclopentene, two products are obtained. Propose a detailed mechanism for the major product formed from this reaction. Explain why the major product is preferred over the minor product. CHEMISTRY 104 Hour Exam I 34. Summer 2009 Page 11 Alcohols are very useful starting materials for the production of a variety of different compounds. Consider the following conversions, all starting with 1-butanol. What reagents (including catalysts) are necessary to convert 1-butanol into the desired product? Some many require more than one step. If more than one step is required, draw the structural formula for the major organic product in each step (this means to include the hydrogens). 15 pts. a) 1-butanol 1-butene b) 1-butanol butane c) 1-butanol 2-butanol d) 1-butanol 2-butanone e) 1-butanol butanoic acid CHEMISTRY 104 Hour Exam I 35. Summer 2009 Page 12 Isoprene is the monomer in natural rubber. The structure of isoprene is 6 pts. CH 3 CH 2 C CH CH 2 a) What is the IUPAC name for isoprene? b) When isoprene polymerizes, two polymers form, the cis configuration and the trans configuration. Draw the cis configuration showing two repeating units and the configuration about the carbon-carbon double bonds. 36. 7 pts. Fiberglass is a condensation polymer formed from the following monomers: HOCH2CH2OH and HO2CCH=CHCO2H a) Draw the structure of this fiberglass polymer showing two repeating units. b) What types of intermolecular forces are exhibited between individual fiberglass polymer chains? c) Fiberglass is a highly crosslinked polymer. What compound can be added to crosslink individual fiberglass polymer chains? Explain how the crosslinks form. CHEMISTRY 104 Hour Exam I 37. Summer 2009 Page 13 For the following, what monomer(s) are needed to form the polymer? Label each as either an addition polymer or a condensation polymer. 8 pts a) CH CH 2 CH CH 2 CH CH 2 CH CH2 n O O b) NH NHCCH 2CNH O O NHCCH2 C n 38. a) How many alcohols have the formula C4H10O? 6 pts. b) How many ethers have the formula C4H10O? c) How many alkenes have the formula C4H10?