CHEM333H_Practice Final Exam_Solution

CHEM333H_Practice Final Exam_Solution - Chemistry 333...

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Unformatted text preview: Chemistry 333 Practice Final Exam December. 7, 2010 CHEM 333 Honors Fall 2010 Practice Final Exam I PSCOOG 9:00-12:00 December '7, 2010 NAME: A “47M ' Be sure your exam has 17 pages, including this page. Read the directions carefully for each problem. Write CLEARLY; illegible answers will be considered incorrect. Do not use red ink. Stop writing and hand in your exam promptly when instructed. Late exams will have points deducted. Please leave quietly if you leave early. 6. Put away all cellphones, pagers, notes, books, etc. You are only allowed a writing implement and molecular models. 9:3?!91‘ 7. Work the easiest Emblems fifit. Question 1 20 points Question 2 16 points Question 3 20 points Question 4 8 points Question 5 20 points Question 6 57 points Question 7 20 points Question 8 31 points Question 9 8 points _ Total ' 200 points Bonus 10 points Score: 210 points Chemistry 333 Practice Final Exam December. 7, 2010 1. Multiple Choice -— put the appmpriate letter in the box 2 pts each (20 pts). a) Which is the correct assignment of the names of the following groups? H H C C to? v M \c/‘L 0? H2 1 2 3 a) l = methylene; 2 = vinyl; 3 = phenyl b) 1 = vinyl; 2 = propargyl; 3 = benzyl c) 1 = allyl; 2 = vinyl; 3 = benzyl d) l = vinyl; 2 = ally]; 3 = phenyl b) Which of the following statements is true? a) All mirror images are enantiomers b) All molecules that have stereocenter centers are chiral , c) Isomers that are not superposable on their mirror images are enantiorners d) Superposable structural isomers are enantiomers ' - c) Which of the following statements is not true regarding resonance structures? 5 a) All resonance structures must have the same number of electrons b) Each atom in all of the resonance structures must have a complete shell of valence electrons c) All resonance structures must have the same arrangement of atoms d) All resonance structures must be valid Lewis structures d) What is the approximate C-O-H bond angle of an alcohol? a) 90° ' b) 109.5° c) 120° «1) 180° - e) Which of the following sets consists of only polar aprotic solvents? 0! a) water, hexane, methanol h) acetic acid, DMF, toluene c) DMSO, ethanol, acetonitrile d) DMF, acetonitrile, DMSO Chemistry 333 7 Practice Final Exam December. 7, 2010 f) Which of the following statements is not true regarding the conformation of C substituted cyclohexanes? a) ring inversion of cyclohexanes between two chair conformations takes place via a boat conformation ' b) substituted cyclohexanes are destabilized by 1,3-diaxial interactions c) the boat confonnation of cyclohexanc is more stable than the chair conformation d) the relative amount of two conformations of substituted cyclohexanes can be determined from the difference in strain energy g) Which of the following is a definition of the rate-determining step of a reaction C mechanism? a.) the first step b.) the last step c.) the step that crosses the highest energy barrier d.) the most exothermic step h) Which of the following concepts explains why tertiary carbocations are more stable C, than primary and secondary carbocations? ‘ a.) electronegativity b.) resonance c.) hyperconjugation (1.) Hammond postulate IE i) What is the major organic product obtained fi'orn the following reaction? 0 0 [—1— 1 2 3 MCPBA /U\/ H“?! in“ HQ“ “We”: Hac H3 Hac H a.) only 1 b.) only 2 c.) only 3 d.) both 2 and 3 j) Which of the following concepts explains Markovnikov’s rule as applied to the & addition of HBr to propene? a.) the relative stability of carbocations b.) the nucleophilicity of bromide anion c.) the acidity of HBr d.) the Aufbau principle Chemistry 333 Practice Final Exam December. 7, 2010 2. 3.) Fill in the substituents on the two chair conformations drawn for the following compound. For the carbons labeled 1, 2, 8L 3, include all hydrogens and substituents. Label each substituent axial or equatorial (a or e, respectively) for carbons l, 2, and 3 for clarity. (16 pts) b.) Assign R or S to the stercocenter at carbon 2? (R) c.) Circle the conformation in part A that is more stable. AG(CH3) = 1.74 kcal/mol AG(Br) = 0.57 kcal/mol AG(D) = 0 kcal/mol d.) Which conformation is the reactive conformation in an E2 elimination? Put a star next to the appropriate chair conformation in part A.. c.) Draw the major product. that would form if you treat this compound with a base to do an E2 elimination N, P__ O BONUS: Does the product follow Zaitsev’s rule, yes or no? (2 pts) No. Chemistry 333 Practice Final Exam December. 7, 2010 3. Synthesis problem: Provide reagents and conditions for ONE of the following synthetic nansfonnations. Put an X through the problem you DO NOT want graded. Be sure to include all Synthetic intermediates. You will need more than one step to accomplish this. (20 pts) (8) OH @— —_—. (5% ‘ . z' r 53W \ B". r; RON“ ®< .— ———_9 . 5+0?!) “' mm EWH$H 0“ in 0 8H,, d; M j , 5-5.4” “m film/v O v, Ho /\ 0" MC 3 \un f7 ”“‘7\/ Wm» Chemistry 333 Practice Final Exam December. 7, 2010 Chemistry 333 Practice Final Exam December. '7, 2010 4. Draw two more reasonable resonance structures (indicating formal charges, of course) for the compound given below and indicate how you obtained them using arrow pushing (electron pushing). With the given structure there should be three resonance structures. Circle the structure that contributes the most (is the most stable). (8 pts) 9 ' 9 I C0 0 a . *9“ :9 (9 6 Chemistry 333 Practice Final Exam December. 7, 2010 5. Mechanism Problem: Draw out the mechanism of the following reactions. Make sure you include all intermediates, and draw curv'ed arrows to show the movement of all electrons. You have all of the reagents you will need. (20 pts) a.) From exam 3’s extra credit. W HBr Br :3 of 4261;! b.) \ 0 Brz. Ho’ “to —-——-—-—-——~———-——-—-a-- \ ‘ "Br J s" f. G (ifir 90 Jay, “0 Y .’ 3‘ " M v F. 9 ._———a Chemistry 333 Practice Final Exam December. 7, 2010 6. Fill in each 'box with the appropriate starting material, reagent or product to complete the scheme. Make sure you indicate stereochemistry where appropriate. If more than one product ean be formed draw the major isomer or just one of the enantiomers. (60 pts) 0” Pcc “WK b-) Br>l\/\ ——-—-——*’ EtOH AN 3) c.) D H 69 @_ W M “a ‘=” .4 ""—'—'—"'"""—." H ' DMF . o d.) - o 0-§-0H3 Na N? 1U} —.——... \ Q o acetone tBU {J}... f.) l/\//\/0H —¥:E(-:———r- \lJt/H Chemistry 333 3-) do h-) j-) Practice Final Exam H2504. HOEt —--—-——-—D~ G) Na BOEt HOEt MCPBA —> 1. 0504 —D- 2. Nan-I303, H20 6 Na E)OH H20 10 December. '7, 2010 Chemistry 333 Practice Final Exam - December. 7, 2010 l.) O 1) 03 )k/WW 2) 3(CH3)2 1) BH3 H —_—’. . 2) H202, NaOH 0'4 Br 6-) e . N H / _a_9_.. /\, H20 L"! p-) 11 Chemistry 333 Practice Final Exam December. 7, 2010 (1-) r.) HVWtr 0 NO” \JLOH t-) t t BONUS: (2 pts) In the previous reactions, which reaction(s) followed Zaitsev’s rule? List the letter of the corresponding reaction(s). -ck),Cn) 12 Chemistry 333 Practice Final Exam December. 7, 2010 7. To answer the questions-below you must be knowledgeable about substitution and elimination mechanisms and how everything is related. Consider the following statements in reference to SN], 8N2, El and E2 reactions of haloalkanes. To which mechanism(s), if any, does the statement apply? More than one answer may apply or the answer may be none. (20 pts) 1) involves a oarbocation intermediate t (T i 2) 'is first order in haloalkane and first order in nucleophile gN 2/ 3) involves inversion of configuration at the site of substitution 1/ 4) involves retention of configuration at the site of substitution fl 0 Y‘fQJ 5) substitution at a stereocenter gives predominantly a racemic product SN | 6) is first order in haloalkane and ....— zero order in base L7 i 7) is first order in haloalkane and E: 1/ first order in base 8) is greatly accelerated in protic solvents : ) of increasing polarity i C l 9) Order of reactivity of haloalkanes is 9N ‘ E I 3" > 2° > 1" 10) Order of reactivity of haloalkanes is 1 E L’ methyl > 1° > 2° > 3° 13 Chemistry 333 Practice Final Exam December. 7, 2010 8. Alkynes can belmade by bromination of alkene compounds followed by elimination. There is a problem though. Out of the two different isomers E or Z alkene, only one of them reacts to give the desired compound. The other gets stuck as the brominated alkene. Answer each of the questions below as it relates to the following set of reactions. (28 pts) Ii 2. NaH (2 equiv) a) Fill in the product of the following reaction. Label any stereoeenters as R or S. (If enantiomers are possible, only draw one enantiorner): E-2-butene b) Fill in the product of the following reaction. Label any stereocenters as R or S. (If enantiomers are possible, only draw one enantiomer): In. Brz 2 Z-2-butene ____._._H__,.. H c) Which reaction gave a meso product? Part (a) or (b)? m) d) The product in part (a) can be reacted with one equivalent of NaH to make the mono brominated alkene. Draw the Newman projection of the product from part (a) followed by the product that can be obtained from elimination with NaI-l. iv ‘ tar yr ' W7C .1equiv.NaH _ “5L Id ' /’\ n 14 Chemistry 333 December. 7, 2010 Practice Final Exam e) The product in part (b) can be reacted with one equivalent of NaI-I to make the mono brominated alkene. Draw the Newman projection of the product fi'om part (b) followed by the product that can be obtained from elimination with NaH. fir HE W 1 equiv. NaH f) If we take the products from part (d) and (e) and react them with NaH one of them can react to form the alkyne product and one cannot react and stays as the alkene, as shown below. Which of the original starting materials can be transformed into alkyne, Z-2-butene or E-Z-butene? Circle one below. circle one 5'2“ 1equiv. NaH fiz-bromo-z-butene W _.._—__ 1 equiv. NaH é—Z-brorno-Z-butene -—-—p no reaction g) Why is Z-2-bromo-2-butene unreactive to Mill? (Hint: think about the orientation for E2 elimination) 15 Chemistry 333 Practice Final Exam December. 7, 2010 9. Follow the instructions below. (8 pts) (a.) Compare the acidity. Circle the most acidic and putting an X through the least acidic. @ ct” 0°“ (b). Compare the indicated bonds. Identify the longest bond by circling the compound and put an X over the compound with shortest indicated bond. (2 pts) i 2H % (6.) Compare the bascity. Circle the most basic compound and put an X through the least basic compound. 0 A09 16 ...
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This note was uploaded on 02/20/2012 for the course CHEM 333 taught by Professor Lavigne during the Fall '09 term at South Carolina.

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CHEM333H_Practice Final Exam_Solution - Chemistry 333...

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