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chem3a-fall02-mt1-Pedersen-soln

chem3a-fall02-mt1-Pedersen-soln - Dr Steven Pedersen...

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Unformatted text preview: Dr. Steven Pedersen October 2, 2002 Chemistry 3A Midterm #1 Student name: ________K€761/_______ ______ _________ Student signature: TA’s name or section number: Problem 1 (30 pts) Problem 2 (30 pts) Problem 3 (30pts) Problem 4 (30 pts) Problem 5 (40 pts) Problem 6 (40 pts) Total Points (200 pts) No Calculators Allowed Be Sure Your Exam has 12 Pages Be Sure To Try All Parts of Each Problem! Bond Dissociation Energies of Various Bonds DH° (kcal/mole) DH° (kcal/mole) ———— ———— Organic Lingo 1A. Provide a systematic name for the following compounds. Use common nomenclature for any branched substituents. (30 pts) 3X1 W (9 B 9- éromo —- 6—- /~(r¥—Aw§/-,Z —C/7/oro —5«- doorway/— nonane B. Draw a structure for the following names. For cycloalkanes use flat rings. For all others use bond-line notation. . 2-cyclobutyl-5,5-dibutyl -2,3,7-trimeth ldecane C3) . 1,1-dibromo-3-isobutylcyclohexane 3‘B( F- [P . trans-1,3-difluorocycloheptane CE I], F; C. We have used many types of arrows to describe various phenomena. in the boxes below, identify each arrow using only a FEW words AND provide a REAL example of how it could be used. D. One or more of the bond-line structures shown below contain improper use of wedge—dash notation. Circle the incorrect one(s) AND explain why they are incorrect. flu's Sap W1” 50% pmmmes “1% 0/1! 7/5?“ The Name is Bond. Molecular Bond. A. Write the Lewis dot structures for each of the following molecules. Be sure to SHOW ALL BONDING AND NON-BONDING ELECTRONS AND CHARGES. G) MeOH 1-. H2CCHCHzBr H3CNCCH3 G) H\ .. GD 4 If! /,< . . 67",) {{\ 69 [M +1—/C "U—‘L’L \a:c-c’-,5r*. M—/C—ME¢—c\—M H H / x; ' I! H 8. Draw two additional resonance structures for each of the following molecules. Your structures must be reasonable. AO/MO 8. (30 pts) A. Which term best describes the 2P,“ 2Py and 2Pz atomic orbitals (circle one): valence nodeless Hund's rule @ regenerate primordial 8. Draw the atomic orbital energy level diagram for 18 through 3P. On the diagram fill in the electrons for 348 (atomic number 16). How many neutrons does 3“S have? ' number of neutrons in 34S /8 atomic orbital diagram for 34S C. Construct the molecular orbital diagram for the cyanide ion, 'CN, using the following guidelines and labeling schemes. BE SURE TO INCLUDE EVERYTHING ASKED FOR BELOW. . Assume that both the carbon and nitrogen are SP hybridized. . The relative energies for carbon and nitrogen are provided below. . Indicate the relative energy levels of any atomic and hybrid orbitals on the left and right hand sides of the diagram. - . Clearly indicate which orbitals are being combined to make molecular orbitals. . Fill in all of the electrons. . Label all the levels as o, 7:, etc. . Label the HOMO and LUMO . / nitrogen ‘ \ / "41‘ ‘H‘ i577, ~—+l-—'76u (-3 molecular orbital diagram for CN Freely Rotating 4. (30 pts) A. Draw Newman projections for the bond line structures shown below. Make sure your projection is representative of the conformation shown. W W H‘H/ \ I (4% C5202 H a (5) Ho ”5% O B. Draw bond-line structures, including wedges and dashes, that exactly represent the conformations depicted by the following Newman projections. 54’ eclipsed O- :0! ‘+ [5 f O t G72 0 K of «5ch H «5/ N \\ CD C. Below is a potential energy diagram that reflects the relative energies associated with rotation about the Cq-Cj bond of 2,3,3-trimethylpentane. Match the Newman projection with each minimum and maximum on the diagram (put the letters in the boxes). Be sure to rotate in only one direction. Hint: Start by eliminating Newman projections that do not match the molecule in question. WXXK H A B C D E F H i H H H H H H H H G H l J K L i. hi “I ll pm E. In the boxes labeled stereoisomer A and B, draw the CHAIR structures for the two stereoisomers of 1-bromo-1,4-dimethylcyclohexane, the product in part A. 02% @acfliflox AG=02-35’ Ac (W26 #24:!) Oz K. /- 7 " —- r 416, (Ban—9v )- ‘5 E .. . conformer of A equulibrium arrows t Aé(m25—»ar)=’-7 (M14: ’zlgh ‘fl”7$_ Sig“ (aefi’mi; +055 AG = 0.55’ stereoisomer 8 show your work! conformer of B F. In the boxes labeled conformer A and B, draw the ring-flipped conformations of stereoisomers A and B. G. Calculate AG for each conformational equilibrium. Place your answer in the boxes labeled AG =. In order to receive any credit you must show your work. H. Using appropriate arrows indicate which side the equilibrium would lie on for each case. the indicated Suhstituent Equatorial tn the [nnlnrmer with the Suhstituent inal A than ein Free Ener an ill in frnmtheE cluhexane Cuntnrmer with _ ’ 'l'llllLH-3 u 111 1111 e u w t Substituent AG“ (kcal mol") Substituent AG" (kcal mol“) 1 0.25 g 0.52 é CH3CH2 1.75 Br - 0.55 “- (CH3)2CH 2.20 1 0.46 (CH3)3C : 5 HO 0.94 t“) HO-C 1.41 CHJO 0.75 i CHJO—C 1.29 age 1.4 \ Note: In I.“ examples. the more stable conformer is the one in which the substitucm is equatorial. a Absinthe 6. Most countries banned the green liquor known as absinthe at the turn of the century due to the presence of thujone, a hallucinogen that, if abused, can lead to serious medical complications. All of the following questions are related to this molecule. (40 pts) thujone A. Would you describe the relationship between the methyl and isopropyl groups in thujone as (circle one): cis resonance equilibria O .2. conformers rotamers 8. Provide a systematic name for the core of thujone. NAME: A/C‘qC/OEBJ-djbxau C3) C. On the structure below label each of the circled carbons as primary, secondary, tertiary or quaternary. 10 E. Draw an arrow-pushing mechanism that is consistent with the following reaction. O . o O\ / H V AW @ F. Show the product you would expect to get from the following arrow-pushing mechanism. 11 ...
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