Exam+1+--+Fall+2006+--+Blank

Exam+1+--+Fall+2006+--+Blank - Name Page 1 I. (20 points)...

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Unformatted text preview: Name Page 1 I. (20 points) A. This year marks the 100th birthday of pharamaceutical chemist Albert Hofman, inventor of LSD. To recognize the occasion, consider the structure of LSD below, and answer the questions about this drug's structure and reactivity (as usual, you should consider other closed shell resonance conmbutors In your evaluanons)‘ (a) For each of the atoms indicated with an arrow, provide the atom's most reasonable hybridization as well as its electronic geometry (VSEPR), and observable geometry (shape).no partial credit Electronic Observable Hybridization geometry geometry (b) How many units of unsaturation does LSD have? ATOM N1 . . . . (c) LSD is absorbed eas1ly into the bloodstream 1n LSD (lysergic acid diethylamide) this neutral form. However, it is ultimately protonated is the process of breaking it down. Circle the most basic site in the structure of LSD. (c) most basic site circled B. Mustard gases are highly toxic, skin—blistering H H H H compounds that were developed for use as chemical Cl_(':_(':_s_é_(':-Cl weapons decades ago. The structure of one of these ['4 1'1 1% l'i compounds, the "sulfur mustard," is shown. sulfur mustard, C 4H 8Cle (a) Do you expect the sulfur mustard to have a dipole moment? 1) Draw a proper 3_D picture that Clearly Indicate molecular dipole or circle: None shows location of all electrons (bonded and non—bonded) around the central sulfur atom (Q other atoms should be shown in 3—D), and ii) indicate the direction of the molecular dipole, or circle "None" ( meaning you expect the dipole moment to be 0) in the box. (b) Several structural isomers can be drawn for sulfur mustard, but one contains the most acidic H atom that can be designed using this molecular formula (C4H8CIZS). no partial credit i)Draw this isomer,keeping all shells closed and all atoms neutral. ii) circle the acidic H, and iii) estimate its pKa, using your pKa table. Name Page 2 II. (22 points) Fill in the missing information for each of the following balanced reactions. Ionic compounds should be drawn in a way that clearly shows which atom(s) carry the formal charge(s). A. Aluminum bonds and behaves in a way that is very similar to its group—mate, boron. (a) Provide complete Lewis structures for all products of this reaction: H Al + H/ \H (b) What is the expected VSEPR (C) Whatls the expeaed VSEPR (electronic) geometry ofthe Al (eleCtTOWC) geOmetry OfIhe Al atom in the starting material: atom "1 thefinal PVOdMCt(S)-' B. Draw all products for this reaction: :0: II H\ /C\ ’ 6') 9 H’C\ Ll .CH3 —> H—C—C\ / I H H H C. Provide the curved arrow mechanism and draw all products for this reaction: (a) Draw all products for this reaction: (19) Circle the Keq that best describes this last reaction: Keq < 10'3 Keq < l Keq : l Keq > 1 Keq > 103 Name Page 3 III. (21 points) (a) Nitrile oxides are very reactive compounds that are useful in organic syntheses. One Lewis structure (a minor contributor) for a simple nitrile oxide is shown below. Provide the other two major resonance contributors for this compound (all atoms must be closed shell, formal charges between —1 and +1). Form A ay be in either 0rd r I? G) .. ..e , H a nitrile oxide (b) Which of your drawings above contributes most to the actual structure (circle one): Form A Form B Forms A and B contribute an equal amount (0) Assuming the hybridization model for all atoms and considering the resonance contributors above, provide an accurate and complete three-dimensional orbital picture for the structure you have drawn as F arm A above. As always, you should use lines, dashes, wedges, p orbitals (lone or overlapping) to show the direction of a_ll electrons (or empty orbitals) in your nitrile oxide. All bond angles should reflect the appropriate geometry and hybridization chosen for your drawing. E (d) Simple nitrile oxides, like the _. ., Cf) one drawn above, rapidly dimerize . . /O\ to form furoxans. Provide the best N N ' curved—arrow mechanism for the \\ // 69 transformation that is necessary to C _ C form the product shown. / \CH H3C 3 pl on to + (e) Draw a structural isomer for your nitrile N "be to Pi 170M formation oxide (molecular formula C2H3NO) that contains: 1) all closed shell atoms 2) all uncharged atoms 3) an sp hybridized C atom, and 4) an sp hybridized N atom. Be sure to draw a complete Lewis structure! IV. A. Name Page 4 (20 points) (a) Nitrosyl fluoride has connectivity FNO and can be drawn as a set of two all closed shell resonance contributors (atoms with formal charges between —1 and +1), one of which contributes more to the actual structure of nitrosyl fluoride. Draw these contributors in the appropriate boxes. only 3 pts if the correct drawings are put in the wrong boxes. must be complete Lewis structures, charges must be shown Most important contributor Less important contributor (b) Considering both of these major contributors, what is the most reasonable hybridization for each atom? hybridization hybridization hybridization F N 0 II II II (c) Using the hybridizations you have chosen, provide an accurate and complete three—dimensional orbital picture for the most important contributor. As always, you should use lines, dashes, wedges, p orbitals (lone or overlapping) to show the direction of a_ll electrons (or empty orbitals) in nitrosyl fluoride. All bond angles should reflect the appropriate geometry and hybridization chosen for your drawing. Oxyluciferin is one of the compounds responsible for the green glow that fireflies emit. Draw the single, best resonance contributor for the mono—anion of oxyluciferin (shown below) that shows how the delocalization of this negative charge involves the other oxygen atom. SH? 4 Name Page 5 V. (17 points) A, The compound shown, CP—690550, is currently being used in clinical trials as an agent for preventing rejeCtion Of Skin grafts' List the bonds indicated in order of their lengths — if any are predicted to be about Bond 2 Bond 3 the same length, put them together in the Bond 4 . . \ / / same box: no partial credit N /\ H3C \ C \ N (93 SN longest N / I \ K Bond 1 shortest CP-69055 0 B. The amino acid cysteine is shown in its fully protonated form. All acidic sites are labeled. For each of the bases given, determine whether that base can successfully (Keq>1000) deprotonate each acidic site (you may assume you have an excess of each base). Put an X in the box next to each site that would be deprotonated successfully — or an X next to none. each base is graded without partial credit : fi : Base A1 A2 A3 None A‘::§_CH_C_§/s H | DEE E 2 CH2 0 II aim” NaO’C‘ONa DEE |:| 2 Cysteine HCECLi |:| 2 C- (a) Three diffferent compounds share the molecular formula CZHZFZ and contain a pi bond. Draw these compounds in the boxes below. Your drawings should accurately reflect the geometry of all central atoms. no partial credit (b) Based on the principles presented in Chapter 1, which of the CZHZFZ isomers do you predict has the the lowest boiling point, and provide a brief explanation for your choice. ...
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This note was uploaded on 01/30/2011 for the course CHEM 210 taught by Professor Capolla during the Spring '07 term at University of Michigan.

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Exam+1+--+Fall+2006+--+Blank - Name Page 1 I. (20 points)...

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