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CHEM%203A%20MIDTERM%201%20KEY

CHEM%203A%20MIDTERM%201%20KEY - Dr Steven Pedersen...

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Unformatted text preview: Dr. Steven Pedersen Chemistry 3A Midterm #1 ‘Bsctetisl Odors October 3, 2007 . g is Student name. ______ K'f ____________________________ Student signature: _____________________________________ TA’s name or section number: _______________________________ No Calculators Allowed No Molecular Models Allowed Problem 1 _________ (24 pts) Problem 2 ________ (20 ptS) Problem 3 ________ (22 pts) Problem 4 ________ (16 ptS) (A'D) Problem 4 ________ (1 8 ptS) (E-H) Problem 5 ________ (6 ptS) (A'B) Problem 5 _______ (14 ptS) , (C-G) iiProblérhiG m’i_7:;r___i_::71 '5 pt§)' Wifiim 77777777777» Problem 7 ________ (15 ptS) Total Points _________ (1 50 PtS) Be Sure Your Exam has 10 Pages Be Sure To Try All Parts of Each Problem! 1 . A. Provide a systematic name for the following compounds. Use common nomenclature for any branched substituents. (24 pts) 91 7,9) ‘33 c 7" r; ”LE W» 5,é ~- c€¢/‘€%/C’C‘¢&¢u‘ ) / .. , ’ d p K” j; é / (1/4/‘P/{jé’ —~ ,2, 3, 3 'VPI} 1M»! 94% 0C 1162111; 2} 92 - (If, h; u’ y’iay(f/JL¢‘71.a—pc€ B. Draw a structure for each of the following names. For cycloalkanes use flat rings. For all others use bond-line notation. > cis-l,3—dibromo—2,Z—dimethylcyclopentane 8r «€744 81/ > Spiro[2.2]pentane l><7 C. The numbering system and language of substituted pyrazines is demonstrated below. Based on this, draw the structures of the molecules named in the boxes. 2,5-dimethyl-3—butylpyrazine 2—isopropyl—5—isobutylpyrazine ' ""”VTff-dicycTwrop'yl-fio’dO‘prO'p'a'nE"""”' ' ”"Wifiiww ‘ ,,,,,7,,,,,m " '7 " iw 2. (l 6 pts) A. Determine the total number of valence electrons for each of the molecules A—F. Place your answer in the box next to each molecule. B. Using the process of elimination, decide which molecule on the left corresponds to the molecular orbital energy diagram on the right. Place your answer in the box provided along with justification of your answer. Your justification must describe how you eliminated the other possibilities. Number of valence electrons ,4 cwi o“ C N=C=N' 29- 2‘7er Justification for your answer: 7 \ - -_ . 4.. C 71M 1; (int? fi/Mw/‘I'tprflap éiéflwfli 87”ng ”(6 5/,“wa ’ , f1 (Li/bur 7) (LL17 Mr? ”[411 /' l'i £19441 . fl£.€:£l:/i‘I—L’Q) I? fIffZLtL 3) ML; 3 céfwwwgg t. (stoma, .m/erqflai' fl“ ' (.(ijLW‘L e ”at; 43/47 /:{(,.( Z, 5.19;»; c4 ,1 L {ft/U 51.<,'C{j¢a 7- [Vi V7 77 (MM am joist” ’3 , ”id" ”'5" "4”" M 6" W “I a .7, :2 /_£ 3 .a .. Max“ (7/ /yc‘>»‘v=é'/g ,. C. On the MO diagram in Part B, label the HOMOflandLlJMO. D. Match each picture with a term. Place the letter associated with the term in the box below the picture. There are more terms than there are pictures. 80%‘00059'QD a. ZS atomic orbital b. n-bonding MO c. 6-bond d. 0-bonding MO e. P atomic orbital f. SP2 hybridized orbitals g. n—antibonding MO h. o—antibonding MO i. Larry, Curly and MO 3. Provide reasonable resonance structures for the following. Two additional resonance structures Three additional resonance structures Hint: If you change the geometry of a given atom in a resonance structure, consider whether the change is reasonable based on geometric considerations. 4. A. For the following equilibrium, circle the correct statement about AG. ,4\ /G>o/ AG=O AG<O B. Justify your answer for Part A using a few words. Do not base your answer on calculations! / [/4151 (L512 med «4’7 c M [LL57 5/ 525,55 519/54 Md??? 55445” Q X / 5L/(’ /5 vu‘ fl/Zw (’ j/ul {Vt/4’1 V 5’ 9 5 A5 VZL (1.5141747 M'Lflicizlfi‘ccy’ SC) V’flté <5 U 555 59 "7/7 L141 (75159055314 A4 C ; fflv; 55/1 1/ ./(/1/L (‘ffu \LL 1: £5pr C 5 ’51 34 I Wei/i c ”(.6555 “*4 55 "1/ , ~ / 7/ . >.7< ("WM ,‘MULK/ —5//55)</5J, 5 5t (/4051 (S/L 57/1 Mix/r 5/ u! /WV4L’ 5/6 5« CW/Q / / S7, C1"?! ‘ U5 Mtg/1 , 1&4 £//>LC[) Cir/45a? ”Ff/(“l ////7,05:z // “/0 “/CJ /57/7<_//1 fjé >5?) C Draw a “flat ““9” view of the compound depicted in Part A. D. On the chair skeleton provided, draw the exact conformation depicted by the Newman projection. Use the numbering system provided in both drawings. H Cl CI H (”Q Ola, H3C - 1 - CH3 1 \ H Q’ ‘6 0| 02 if“ Cl 4 H l :92 OZ H Continued on the next page , E. Draw a Newman projection looking down the bond indicated. w "\. «Wm 53) 67““ g. 5 Kid \ $ 7 7’4 0’ CM H F. On the Newman projection you drew for Part E, clearly label ALL gauche interactions. Any incorrectly labeled interactions will cancel correct interactions. G. Draw diaxial—l ,4-dibromocyclohexane and diequatorial—l ,4-dibromocyclohexane. In the box between the two structures, indicate the direction of the equilibrium (K) between these two conformers. diaxiaI-1,4-dibromocyclohexane diequatorial-1,4—dibromocyclohexane H. Using the numbering system given, draw the chair-chair conformation of the molecule on the left. Start your drawing with the chair on the right below. Be sure if rrrrrrrrrr eflhemhelocationflandhorientationmr substituents... ”Hafi‘mvfliii - ,, a we: . S. A. Draw a Newman projection that accurately represents the conformation depicted in the bond-line structure. Newman Projection B. Which potential energy diagram shown below best represents rotation about the indicated carbon-carbon bond. Circle one. rotation about this C-C bond ° 120° 180° 0° 60° 120° 180° 240° 300° 00 60° 120° 180° 240° 300° Continued on the next page . C. Draw a Newman projection that accurately represents the conformation depicted in the bond-line structure. Newman Projection D. For the molecule shown below (on the left), draw Newman projections of all three staggered conformations. Notice that the back carbon atom is already provided for you in the boxes. staggered conformation staggered conformation staggered conformation E. ldentify the lowest energy staggered conformation in Part D by writing the box letter here:___/;\___ F. Identify the highest energy staggered conformation in Part D by writing the box letter here:____6____ , , .,.G.,Draw-a bond-line structure that exactly,mmesentsthe Newman prOJe,§t_i0n,, shown below. You must use wedges and dashes in your structure. bond line structure 6. A. Draw ALL of the product(s) you would expect to get based on the arrow- pushing diagrams shown below. 0 p «.2va <3. .___. l B. Is the reaction shown directly above considered: Circle one an initiation step a propagation step“ a termination step /,. \ r, a baby step a dance step “one small step for man” 7. A. Add arrows to the structure on the left to indicate electron movement leading to the products. 0 09 _—> /S\ \Cg- g/ CC? + l Hint: no radicals involved B. Add arrows to the structure on the left to indicate electron movement leading to the middle product. Then add arrows to the structure in the middle to indicate electron movement leading to the final products. 0M9 OMe Hint: no radicals involved C. The reaction shown below proceeds through a diradical intermediate. First add arrows to the structure on the left to indicate electron movement leading to the middle product. Note, that you will have to add the structure of the middle product based on your proposed mechanism. Then add arrows to the structure in the middle to indicate electron movement leading to the final products. D a diradical The Scorpiul nostril, mad the high head gather not the odors thet Lie on the track of truth. George Eliot, Felix Holt, the Bgdicgl, "1866 if) ...
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