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Exam 3 key - Chemistry 3 3 3 NAME lit ll RECITATlON DAY Be...

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Unformatted text preview: Chemistry 3 3 3 NAME: lit ll RECITATlON DAY: Be sure your exam has 12 pages, including this page and a reagent page. Exam 3 CHEM 333 Fall 2010 Exam 3 November 1 l. 2010 Read the directions carefully for each problem. Nov. H, 2010 Write CLEARLY; illegible answers will be considered incorrect. 0n questions requiring derivations or calculations, show your work in a manner that can be easily understood. Avoid even casual glances at other students“ exams. . Do not use red ink. Stop writing and hand in your exam promptly when instructed. Late exams may have points deducted. Please leave quietly if you leave early. Put away all cellphones, pagers, notes, books, etc. You are only allowed a writing implement and molecular models. Work the easiest problems first. Question 1 Question 2 Question 3 Question 4 Question 5 Question 6 Question 7 Total Bonus Score: 10 points 16 points 18 points 20 points 10 points 16 points 10 points 10 points 100 points 110 points Chemistry 333 Exam 3 Nov. 11, 2010 1. Multiple Choice k put the appropriate letter in the box 2 pts each (10 pts). a) The reaction of lebromopropane With sodium iodide gives l—iodopropane. What is the effect ofcuttiri g the concentration of Nal in half on the rate of the reaction? a. the rate remains the same b, the rate decreases by a factor of 2 c. the rate increases by a factor of2 d. the rate increases by a factor of 4 b) Which of the following concepts explains why tertiary carbocations are more stable than primary and secondary carbocations? a.) electronegativity b.) resonance 0.) hyperconiugation CL) Hammond. postulate c) Which is the correct assignment of the names of the following groups? f5 A31 Q; 1 2 3 a. I 2 methylene; 2 = Vinyl; 3 2 phenyl b. i 2 Vinyl; 2 m propargyl; 3 I benzyl c. 1 I allyl; 2 "w“ Vinyl; 3 I benzyl d. i m Vinyl; 2 : allyl; 3 x phenyl d) Which of the following sets consists of only polar aprotic solvents? a. water, hexane, methanol b. acetic acid, DMF, toluene c. DMSO, ethanol, acetonitrile d. DMF, acetonitrile, DMSO e) Which of the following is a definition of the rate—determining step of a reaction { it mechanism? a. the first step b. the last step c. the step that crosses the highest energy barrier d. the most exothermic step Chemistry 333 Exam 3 Nov. 11, 2010 2. Answer each of the questions below with regards to the following reaction. (16 pts) 3..) F ill in the product of the following reaction. far b) Draw the intermediate in the above reaction. 0) Draw the transition state of the rate determining step (rds) in the above reaction. gffijgw‘k “533 d.) Draw out the reaction coordinate diagram for the exothermic reaction above. Label the starting material, intermediate, rds, and product. Energy reaction coordinate a .3 Chemistry 333 Exam 3 NOV. 11, 2010 6) Fill in the product of the foliowing react-ion H _ I DMF {:5 §:“\§:\v\ ,3? Chemistry 333 Exam 3 Nov. 11, 2010 3. Fill in each box with the appropriate reagent or product to complete the scheme. Make sure you indicate stereoehemistry where appropriate. If more than one product can be formed draw the major isomer orjust one of the enantiomers. (i 8 pts) 21) )a§‘§‘“i~ QfiCNK XA EtOH Br b.) @6 «5‘? Na OH ""”Ci H20 Chemistry 3 33 Exam 3 Nov. 11,2010 4. To answer the questions below you must be knowiedgeable about substitution and elimination mechanisms and how everything is related. Consider the following statements in reference to 8N1, 8N2, El and E2 reactions of haloaikanes. inechanisrn(s), if any, does the statement apply? More than one answer may apply or the answer may be none. (20 pts) To which involves a carbocation intermediate is first order in haloalkane and first order in nucleophile involves inversion of configuration at the site of substitution involves retention of configuration at the site of substitution substitution at a stereocenter gives predominantly a racemic product we xi 6) is first order in haloalltane and zero order in base Cf 7) is first order in haloalkane and E:\ caret?” first order in base \j: gab“ V 8) is greatly accelerated in protic solvents C? C, 2» N“ A (1&4; of increasing polarity Q) sf;\ / / «5/ 9) Order of reactivity oi‘baloalkanes is 30 > 20 > 10 k C (Asst \' (ism <11» -{%‘_’\ \ may or (‘1\\"€;‘> {"‘x" 6 Chemistry 333 Exam 3 Nov. 11, 2010 5. Draw out the mechanism of the following reaction. Make sure you‘lnclude all intermediates, and draw curved an‘ows to Show the movement of all electrons. (18 p18) 04 w—wM OH heat Chemistry 333 Exam 3 Nov 1 1, 2010 6. Alkynes can be made by bromination of alkene compounds followed by elimination. There is a problem though. Out of the two different isomers E orZ 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. (16 pts) R \ a Brlfg “.1 4’13 < . - {dc 1 equiv NaNH2 H*“H’H -———~M~W-—fi> Me Me A Br D we 1 e . quw NaNH2 < HicquMe MW ? Me H B a) Label each of the above stereoeenters in compounds A and B as R or S. tall-o; 13) Which of the above compounds is chiral, A or B? c) Fill in the Newman. projections for both compounds A and B. Draw the conformation that will lead to the elimination of the H* and Br’I< (starred HBr). \l’t‘ Llelts W rte \l \\ Trans, W\ C % km “‘6“, 5% ‘r’f- E531} gr“)? A B d“ f! Chemistry 333 Exam 3 Nov. ll, 2010 (1) Using the conformations you drew in part c draw the resulting 'oducts from elimination of one HBr (the starred HBr) from each starting material. :égfgpx Br Br* 1 equiv NaNH2 < HMIHHH WW Me Me A Br Br" 1 equiv NaNH2 < H*“M’Me Me H B 6) Label the products in part d as E or Z. t) if we take the products from part d and react them with another equiv of NaNHg one of them can react to form the alkyne product and one cannot react and stays as the alkene. Which of the original starting materials can be transformed into an alkyne, compound A or B? (Hint: think about the orientation for E2 elimination) t 1 l i .33 sigma Chemistry 333 Exam 3 Nov. 1. i, 2010 7. Synthesis problem: Provide reagents and conditions for the following synthetic transformation. Be sure to include ali synthetic intermediates. You will need more than one step to accomplish this. (10 pts) or 3 , E ii E \m a 5 i“ 3“ Lit?) {15¢- a _ k n w M u“...m...m..wWWW Holt}; M [/Kfffi ? L E)?” X M V n K ““ KW i // '”"“--.._ . U \ / “Mmi‘m/ NCC‘NE\\\ a i N 2;: E21?» H §‘ SW. 6" Obkh \f x? \ KL :3“ W1" 10 Chemistry 333 Exam 3 _ Nov. ll, 2010 BONUS (l0 pts) - 3.) Which of the following sets consists of only polar protie solvents? (4 pts) A a) water, acetic acid, methanol b) acetic acid, DMF, toluene 0) DMSO, ethanol, acetonitrile d) DMF, aeetonitrile, DMSO b. ) What 13 the con ect order of stability of the following earboeations (more stable > less Ci“: @stable)? (4 pts) HELE>2>3 b2>l>3 e2>3>i d3>2>1 c.) How many classes has Dr. Lanni taught? (2 pts) 11 Chemistry 333 Exam 3 Nov. 11. 2010 List of ReagentS: 3T2 C12 - 1.) BE"; , 2.) 2 eq. NaNH'g / NH3 (1) Hg/ Pd HQ/NiZB Hz/CHCO3 (“flak NaO/ NH3(1) Cone. HgSOdhea‘: 1) NaNHg 2) primary alkyl halide 12 ...
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