Download 6 Solved MCQs on Resonance Stabilization of Conjugate Acids | CHEM 231 and more Study notes Organic Chemistry in PDF only on Docsity! 1 CHEM 231-Davis Organic Chemistry Examination I Feb. 17, 2006 YOUR NAME __________________________ (Last, First) DISCUSSION SECTION #53 _____ Instructions • Fill in your name in the space above and on the next page • Put your discussion section number in the space provided. • Print the initial of your last name in the box above • Please sign the Honor Code acknowledgment on the following page • DO NOT OPEN THIS EXAM UNTIL INSTRUCTED TO DO SO • Provide your answers in blue or black pen. Cross mistakes out completely • Answer questions in the spaces provided Initial of Last Name 2 CHEM 231-Davis, Examination I YOUR NAME __________________________ (Last, First) University Honor Code Acknowledgment I have neither given nor received assistance in taking this examination. Signature Notes • This exam is worth 150 points • There are 7 Problems on pages 3-8. Make sure your exam has all the pages. • Nothing written on page 9 will be graded-this is for scratch work • The exam period is 50 minutes. Points Problem 1 (20) Problem 2 (15) Problem 3 (15) Problem 4 (20) Problem 5 (25) Problem 6 (15) Problem 7 (40) Total (150) EXAM BEGINS ON NEXT PAGE 3 5 5. (25 pts) Bronsted Acids-Bases. Shown below are some pKa values for the boxed H atom in a variety of functional groups. Use this information to help answer the following questions. For each of the multiple-choice questions below, circle the correct answer. a). Which of the following compounds is the strongest acid? Circle it. b). Which of the following anions is the strongest base? Circle it C). Circle the best estimate of the equilibrium constant (Keq ) for the following reaction: Keq>1 Keq=1 Keq<1 H CH3 O H CH3 N H CH3 H H H H O O H H H CH3 H CH3 N H O O pKa= 16 35 48 pKa= 5 18 20 H CH3 N H CH3 N H H O O CH3 + O O CH3 + H CH3 O H CH3 N H H CH3 N H O CH3 O CH3 HH O O CH3 6 d). (10 pts) Below is a free energy diagram that shows the energy of the species on the left side of this reaction equation. Based on your knowledge of acid-base theory draw the structures of the reaction products (the conjugate acid and base on the left side of the equation) at their most appropriate energy level of the 3 possible energy levels provided below. Energy CH3 HH H O O CH3 + Conjugate Acid + Conjugate Base CH3 HH H O O CH3 + Reactants Products CH3 HH O O CH3 +H 7 6. (15 pts) Acetic acid is also a base, and it can be protonated by sulfuric acid (H2SO4) either on its double bond oxygen or on its single bond oxygen. Draw comparative structures that clearly illustrate why the double bond oxygen is more basic than the single bond oxygen in acetic acid. H2SO4 + H3C O O H H3C O O H H+ HSO4 _ + H3C O X H H + H3C O O H + H H3C O O H H+ H3C O O H H + H3C O O H H +2X H3C O O H H+ BETTER RESONANCE STABILIZATION OF CONJUGATE ACID _ Poor Resonance Form
