Page 1 I 21 points Viagra is a top selling pharmaceutical marketed by Pfizer 2 3 billion sales in 2009 that is used for the treatment of erectile dysfunction and pulmonary arterial hypertension It is also becoming an accepted treatment for high altitude pulmonary edema which can occur when people attempt to climb tall mountains Name Atom N2 O O S N Bond A Bond D N H3C O N H N O Atom C1 CH3 N N Atom N1 Bond B Bond C CH3 Atom N3 Atom O1 CH3 a For each of the atoms indicated with a thin arrow provide the atom s most reasonable hybridization and electronic VSEPR geometry Hybridization Atom N1 Atom N2 Atom N3 Atom O1 Atom C1 sp2 sp2 sp3 sp2 sp3 Electronic Geometry trigonal planar trigonal planar tetrahedral trigonal planar tetrahedral Molecule 1 2 2 2 2 2 c Molecule 1 is structurally related to the right most ring of viagra Draw a hydrogen bond between a single molecule of water and the best hydrogen bond acceptor present in Molecule 1 d How many units of unsaturation does Molecule 1 have OH 3 3 Viagra b Indicate the relative lengths of bonds A D shown above with the bold arrows by writing the letters in the appropriate boxes below in order of their length A D B C CH3 N N CH3 Longest Bond increasing bond length Shortest Bond no partial 4 H O H no partial 4 Page 2 II 23 points A a The most significant resonance form of aminoketene is shown below However the actual structure of aminoketene can be represented using a collection of three significant resonance contributors in which all atoms have closed shells and formal charges of 0 1 or 1 Draw the other two best resonance forms in the order of their significance in the boxes below Place the second most significant contributor in the middle box and the third most significant contributor in the right hand box Be sure to include all formal charges and draw in non bonded electrons 4 once if both resonance forms are correct but are in the incorrect boxes Name NH2 C C H O aminoketene Most significant resonance form NH2 C C H O 4 no partial aminoketene resonance form Second most significant b Provide a three dimensional orbital representation for the most significant resonance form of aminoketene Use lines dashes and wedges for sigma bonds and to indicate the directionality of localized non bonding electron pairs Draw overlapped p orbitals for pi bonds Be sure to carefully consider whether nonbonding electrons are localized or delocalized when assigning hybridization geometry H N H H C C O OR NH2 C C H O 4 no partial aminoketene resonance form Third most significant sp2N 2 sp2C 2 spC 2 spO 2 H N H pi bonds and delocalized nbe in p orbitals 3 no partial on this C C O H 11 B Draw a complete Lewis structure for a C2H5N3 isomer that fulfills the following criteria There are no formal charges on any atoms All atoms are closed shell The molecule contains exactly one H bond donor The molecule contains exactly one pi bond All N atoms are sp2 hybridized Be sure to draw in non bonded electrons H N N N H3C H N N N OR OR H H3C N N N note there is at least one additional correct answer that is not shown here H N N N OR no partial 4 H O Page 3 III 19 points A a The amino alcohol 2 shown below can be obtained through reduction of tyrosine a naturally occurring amino acid Derivatives of 2 have been examined as potential anticancer agents Name a Circle the most acidic proton in amino alcohol 2 3 b Which of the following bases can completely deprotonate Keq 103 the most acidic proton in amino alcohol 2 circle all that can Na Br Cs O O CH3 K O CH3 H O H N H Na H Na NH2 H H N H no partial 4 Amino Alcohol 2 b Reduction of the amino acid phenylalanine provides an amino alcohol 3 that is similar in structure to 2 above Using the pKa table as a guide to estimate acidity and basicity provide the structure of the major species present in a pH 6 solution of 3 Be sure to include formal charges and non bonded electrons if as necessary H O H N H H O N H H H Amino Alcohol 3 amino alcohol 3 at pH 6 no partial 4 B The pKa of the most acidic proton in molecule 4 is different than the pKa of the most acidic proton in molecule 5 Indicate which of these two molecules has the most acidic proton and provide a brief written words only explanation of your answer O O H O H O Molecule 4 C N Molecule 5 The molecule with the most acidic proton is Molecule 4 Molecule 5 circle one The electron withdrawing CN group will stabilize the conjugate base through an inductive effect which will increase the acidity of molecule 5 no partial Brief Explanation Words Only 4 C The length of the carbon nitrogen bond in molecule 6 is different than the length of the carbon nitrogen bond in molecule 7 Indicate which of these two molecules has the shorter carbon nitrogen bond and draw the single Lewis structure with all atoms closed shell that best explains your answer Be sure to include all formal charges and draw in non bonded electrons O O H2N O H2N Molecule 6 Molecule 7 H2N no partial Lewis structure that explains your answer 4 The molecule with the shortest carbon nitrogen bond is Molecule 6 Molecule 7 circle one Page 4 IV 21 points A Meldrum s acid shown below is used as a starting material for the synthesis of a number of useful molecules with varied biological activities This molecule is a relatively strong acid and has a pKa of 5 a Provide the equilibrium constant for the reaction between Meldrum s acid and trimethylamine Your answer should be in the form Keq 10x fill in the box with the number that represents x Also draw the Lewis structure for one of the two most significant resonance forms of the conjugate base of Meldrum s acid Be sure to include all formal charges and draw in non bonded electrons Name O H O O H Meldrum s acid pKa 5 N CH3 3 Trimethylamine O 4 Keq 10 O O O H O OR answer between 4 6 ok 3 most significant resonance form of conjugate base of Meldrum s acid no partial O O O H O 4 H N CH3 3 b Meldrum s acid is thermally unstable and when heated to high temperatures undergoes a reaction that produces three products as shown by the curved arrow formalism One of these products is carbon dioxide CO2 Draw the structures of the other two products in the boxes below Be sure to put the correct structure in the box corresponding to its chemical formula Be sure to …