whalen1 2008 key

whalen1 2008 key - Return my exam in class Return my exam...

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Unformatted text preview: Return my exam in class Return my exam in Clark 278 NAME __ Q [4L HOUR EXAM l 1. (10, 1 each) Below is shoWn the structure of an organic compound having a large number of different kinds of bonds in it. Some of the bonds have been indicated with an arrow. Beneath the structure is a list of different types of bonds described in terms of their component orbitals. Each bond listed is designated by a letter. In the space provided on each arrow, write the letter that best describes that bond. When two letters are required, theyr may be written in either order, An example has been filled in. A letter may be used more than once. liq :1: H’ -- *cx . H u 3/ e A. spa-spa, o B. spa-spa o C. spa-3p. o D. Spa-p, o E. spa-s, o F. spa—spz, o G. sp2~sp. o H. sp‘rg-pr o J. 5:32-15, 5 K. p-p, o L. sp-sp. o M. sp-p. o N. sp-s, c F'. 5-3. c Q. s-p, o R. 2 p—p, 11: S. p-p, ‘lt T. sp-p. r: V. spZ—p, r: W. spa-p. 1: 2. (14, 7 each) in the space provided, write the correct lUPAC name for the compound having each of the following structures. Be sure ou use correct unctuation and s ellih in our names. H Clesc CH3HCH3 C 3\3/ H3 CH3CH20 ‘CH CH3 0 a‘ CH CH écu (I: H once 10‘ 7 L1 3 a 2— " 2‘ _ 2 r3 rt 7 (or '5 ‘ll % z I 2 no2 Cl CHZCHg 1 \O a. Lil—’WMMBF (rd/lion) ’ [o‘bl’l‘oxy— “lo alsoer'ofvielrmfl’kilm bl 7)- JrgfiriulyL l+ WCIOPQMJH‘ J’l’ WclonVoxj- l~ ill {WJONVJWM Hour Exam I (3), Chemistry 301. Spring 2008. Page 1 of5 pages 3. (7) Below is shown a contributor to the hybrid structure of an intermediate we will discuss next semester. a. (6, 3 each) in the space provided beside two of the atoms, write the formal charge on that atom. a geriodic table is provided at the end of the test. SHOW YOUR WORK. (}_C’/a— Formal charge = Ll'Ll 3 O '— — Formal charge= [GTE—Q) 5' +{ intermediate b. (1) The fonnai charges on the remaining atoms are at.l zero. Based on the formal charges you determined for the two atoms, tell whether the intermediate is neutral overall or is an ion, and till in its net charge if you think it is an ion. CHOOSE ONE. The intermediate is neutral. é The intermediate is an ion having a net charge of + l . 4. (7) The contributor to the intermediate hybrid is repeated below. All valence electrons are included in the structure. a. (4) in the space provided to the right of the given structure. draw the structure of another contributor to the resonance hybrid for the intermediate Be sure to include any unshared valence electrons in the structure you draw as well as the formal charge on anmm that has one. (it is not necessary to show how you determined the formal charge.) b. (2) On the given structure, correctly draw a curved arrow or arrows showing the electron movement required to go from the given structure to the one you drew. H H w si 00%: a WE‘RE H “>0 lmwttfitcod'etm L c. (1} Circle the phrase that correctly completes the following sentence: Relative to the structure that was given in part a. the structure t drew is alan contributor to the hybrid. CIRCLE ONE EQUALLY STABLE MORE STABLE 5. (8) Draw the structure of any organic compound having molecular formula C5H9N04 that includes a carboxylic acid, an amide, and an ether among its functional groups. BE SURE that all atoms in your structure make the correct number of bonds as indicated by the symbolism you use. to ' Q [film msww fossrlle) intermediate Hour Exam I (a), Chemistry 301. Spring 2008, Page 2 of 5 pages 7. (10) To the right is shown a Newman projection for a specific staggered conformation of 1,2- dimethoxyethane as viewed from carbon 1 to carbon 2. H a. (5) Nearthe Newrnan projection is shown the [Vii-‘30 H H ; x H \ beginning of a wedgefhash structural formula for the same compound. The hash bond on each C has been CHng H . —. provided. Complete the wedgefhash structure so that H ' it represents exactty the same conformation as is H is shown in the Newman projection. 0+ 00% b. (3) On the circle to the right, draw a Newman MW“ projection of a different staggered conformation of 1.2 WLQMZ) 0&3 dimethoxyethane from the one that was given. H O jaw-[u c. (2) Tell whether the new conformer you drew in answering part b is more stable, equally as stable, or less stable relativa to the conformer th twas given to you. CIRCLE ONE. more stable equally as stable less stable 8. (9) Below is shown one of the two chair conformations of a stereoisomer of 1,3,5—trimethoxycyclohexane. a. (7) Next to the given structure, draw the other chair conformation that would result were the given structure to undergo a "ring flip.” WHEN DRAWING THE NEW CONFORMATEON. DO NOT ROTATE THE STRUCTURE OR TURN lT UPSlDE DOWN. Be sure all axial and eguatorial bonds are drawn accurately in your representation. } H col-i3 H 3 OOH} CH3o I H _" — H H OCH3 H lli our3 1am 00% b. (2) Tell whether the structure you drew is more stable, less stable, or equally as stable relative to the given structure. CIRCLE ONE. more stable equally as stable less stable Hour Exam l (a), Chemistry 301, Spring 2008, Page 3 of5 pages 9. (5) Hydroxamic acids are a functional group common in many pharmaceuticals. The pi<a for removing the NH proton from the hydroxamic acid below has been estimated to be 8. One possible base that we might try to use to deprotonate the hydroxamic acid is methanethiolate. The pKa for deprotonation of methanethiol, which is the conjugate acid of methanethiolate. is about 11. a. (4) Using the method described in class, estimate the equilibrium constant, Keg, for the deprotonation of the hydroxamic acid by methanethiolate as shown in the following equation. SHOW YOUR WORK. 0 O ('3' OH + CH a?) (5 0H CH " “‘3 5 / ‘fi’ 3",; “w:—' / «I» "' 313.” : cH3 H CH3 --e [O —_-. [0 7m?) hydroxamic acid methanethiolate hydroxamate methanethiol [9,93% PK?»le b. (1) Based on the standard established in class tell whether methanethiolate would be useful for deprotonating the hydroxamic acid. CIRCLE ONE: no, need a stronger base 10. (20) On the next page is shown the energy diagram for the steps in the reaction of 2-methyl-2- brornopropane with hydroxide ion to give 2—methyt-2-propanol and bromide ion. The reaction is shown above the diagram, along with the steps in the mechanism. Various features of the diagram are indicated by letters. Two letters designate the coordinate axes, five letters designate the minima (low points) and maxima (high points) on the curve, and the remaining letters show the vertical distances between various minima and maxrma. a. (1) Based on the relationship between starting materials and products. what classification best describes this reaction? CIRCLE ONE: Addition Elimination Rearrangement b. (1) Are the bond cleavages in the mechanism shownor HOMOLYTIC? (Circle one) c. (16, 2 each) Below and on the next page are eight statements concerning the reaction, the mechanism given, and the interpretation of the diagram. Choose the letter from the diagram which best depicts what is said in each of the statements and write that letter in the space next to the statement. A letter m be used more than once. Some will not be used at all. g 1) The relative Gibbs free energies of reactants, products, transition states and intermediates are described along this axis. CI 2) The energy of the intermediate carbocation, (C‘.H3)C+ Br—, and OH- is indicated by this point on the diagram. E 3) This point establishes an energy for the products to which other energies can be related. N 4) The AG°reaclion for the second step in the mechanism is shown to be strongly negative by the energy difference indicated by this letter. L 5) The overall energy change for the reaction, AG‘Leacu-on, is shown by this energy difference to be negative. Hour Exam I (:3). Chemistry 301. Spring 2008. Page 4 of5 pages D 6) According to the Hammond postulate, the transition state reached at this point should be structurally more similarto the reactants from which it is formed than the products to which it is leading, M 7) The activation energy, Ea, for the second step of the mechanism is the energy change indicated by this ' letter. I 8) The energy difference indicated by this letter shows that the conversion of 2-methyl~2—propanol and bromide ion to (CH3)3C+ Br- and OH- has a positive AG° reaction- d. (2) Using the estimation method described in class, would AS" for the overall reaction most likely be less than zero, greater than zero, or approximate! zer . E ONE Less than Zero Approximately Zero Greater than Zero :é‘r: __9 :6in H 9 Overall reaction: //0\ + @H E //C\ + :5.“ CH30H30H3 CH3 CH3CH3 2 n .. e C?“ .9 e '5.“ "e Steps in accepted mechanism: 1) /C + :9H m /C\ + :_QH CH3 [\CH CH3 I CH3 CH3 3 CH3 ‘ (3 Br- gm’e (PH + e 2) + :OH C F: / J \ .. // \ CH CH CH3 CH3 3 3CH30H3 'Tl Hour Exam l (a). Chemistry 3m, Spring 2008, Page 5 of 5 pages ...
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whalen1 2008 key - Return my exam in class Return my exam...

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