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CHEM 255 Exam 1

CHEM 255 Exam 1 - Chemistry 255 Exam I Fall 1999*ALL...

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Unformatted text preview: Chemistry 255 Exam I Fall 1999 **ALL ANSWERS MUST BE IN INK** Name C Vii ID# Please read the following questions very carefully. 1. Provide Lewis structures for the following compounds (provide formal charges where appropriate): (10 pts) a) CH4O b) CH202 2. Provide structures for the following molecules; (12 pts) /. u 7 S at.) pflfigfl a) isopropylcyclopropane b) 6—ethyl—2,3 ,4,5 —tetramethyloctane A, A, n .4 WW OG’i’NJL. r / g I 2 70/1: W awn-“C32 (q {QM/w, .1. O£ Soésjljfipgcb 3. Provide IUPAC n e following compounds: (12 pts) , a) MA Zip/'42 19x soésduw‘vwl MW /_’_____...._~. m cm gig/[:64 5x £05574,de A noun W 3W A . £3 , CLL4 -_ W — 92 - m KC [OMKJWL_ 4. Draw Newman projections for the lowest energy and highest energy conformations of butane looking down the C l—C2 bond of the butane chain. With the following information, predict the difference in energy between the highest and lowest energy conformations (torsional strain resulting from eclipsed C—H bonds is 1.0 kcal/mol and that for eclipsed CH and C-C bonds is approximately 1.5 kcal/mol) (15 pts) H log/CH3 Energy difference: M @ V 3 5. Circle the three types of functional groups in the molecule below and provide the name of each of these functional groups. (15 pts) from odoriferous fungus Lentinus lepidus 6. Provide fly; constitutional isomers with the molecular formula C7H16. 3 @ (15 pts) 7. Indicate the hybridization for the atomic orbitals of all non—hydrogen atoms in the following molecules, AND indicate the bond types involved in the bonds designated with an arrow: (16 pts) 8. Indicate whether the highlighted bonds would be ionic, polar covalent or nonpolar covalent. (6 Pts) Wchmfid b) C) P l /N—O\ Li—Cl 0 {pm Calm.” a) Y H3C—-OH 9. Draw the lowest energy chair conformation for trans-1,4—dimethylcyclohexane showing all axial and equatorial hydrogens: ( l 9 pts) 5 10. Which of the following molecules have a plane of symmetry (circle those that have a plane of symmetry)? . (9pm) 3 19m a/\ Wf'C/MOQL O 11. Provide an R or S assignment to the following stereocenters. 6 (6 pts) 3 Vb a) OH L H\\‘“* 6 H3CH2C CH 3 1)) Br H3 C\\\\)\ NIL) H Cl 12. Arrange the following bases from strongest to weakest, and provide a detailed rationale for your choice based on t_y_v_g of the following: inductive effect, electronegativity, resonance, bond dissociation energy. - (15 pts) H3C—S- HBC—O H3C—NH— A B. C C strongest base weakest base Rationale: WWMU)"MMJWWm0/5 MW 5 f /5 L044 1% 7‘29 flzcflc. GPA/flaw (3%} (0 v d ( SS 0 M 2,3 Ax.) .fl4jce/Ea E credit problem: @533» What is the pKa of CH2=CH2 Llth ,/ ""’ “ > a ., I/ . “within i 5 pKa 11$}ny ...
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