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Chem210-1-2008-Exam2-Answers

Chem210-1-2008-Exam2-Answers - Chem 210-1 Mid-Term Exam 2...

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Unformatted text preview: Chem 210-1, October 31, 2008, Mid-Term Exam 2 NAME: A N S W 5R3 This exam has 100 total points with the point breakdown for each problem given below. 1. (20 points) The following alkyl halide reacts with NaCN in a dipolar aprotic solvent: CEB. CH3 A) (5 points) Label the asymmetric carbon atoms in the alkyl halide and assign their R,S configurations. B) (5 points) Give the structure of the enantiomer of the alkyl halide shown above. C) (5 points) Show the mechanism of the reaction of NaCN with the alkyl halide. D) (5 points) Assign the RS configurations to the asymmetric carbon atoms in the product formed from the reaction of NaCN with the alkyl halide. A5 0: 6) <1ng 2. (20 points) The following compound undergoes solvolysis when heated in ethanol to give the indicated productsz‘ H flB' EtOH H heat Compound 1 Compound 2 A) (5 points) Assign the R and S configurations of the asymmetric carbons atoms in the chiral alkyl bromide starting material. B) (10 points) Write a detailed mechanism that shows how compounds 1 and 2 are formed. C) (5 points) Are compounds 1 and 2 chiral? If so, assign the RS configurations of their asymmetric carbon atoms. Fail PAICT 8'- Ph =- ‘ U“) \/ H cs) Q (EA EtlDl + _ 3) ©2911 -——--‘9A Pl. + Bx H l H H H5508: 3“ P“ *3) +2: —*7 QM “9cm HoEt ca” 099 C>/U0 FolMflT/ou aF CA/é600/1‘77N/ 2550475 /A/ flACEM / 24m 0 2 39(20 points) Given the following molecule: no r \c a 8‘ \ H3C CH3 B Compound A A) (5 points) Draw a Fischer projection of compound A. B) (5 points) Compound A is treated with NaOEt. Give the product and its IUPAC name. C) (5 points) Treatment of compound A with NH3, followed by an excess of CH3I, then treatment with Ag20/H20 and heating produces a new compound B. Give the structure of compound B and give its IUPAC name. D) (5 points) The hydrogen atom on the 13-03er of compound A is replaced by a bromine atom to give compound C. Is compound C optically active? (2 points) Draw the structure of C and its mirror image to justify your conclusion (3 points). CH \ Pl) CH mm] ”a Pl): ~ 8) \qu 3 / \WA 011 ‘ H Cltg ‘ :5; x ”‘3 'th»2,3-- or film “if 637. tint/m - 2"3— (; ‘ . Mfiztj/u—z sPh . _. ' - 4W ‘\ . (S) :1 3 ((714.1 f . » .~ .— ., CH ’ - 3 _ - ,. C) (”2’ (i LC+ 3 tug)- garéu’thd/juJ-FM Pl: Z]. (20 points) Shown below are two isomers of bromocyclohexane having some of their hydrogens replaced by deuterium. It is well known that breaking a 0—H bond in the rate determining step of a reaction occurs 7-9 times faster than breaking a 0-D bond. H D D H "“ Br V“ Br H D 1 2 A) (/s’points) Show a detailed mechanism for the E2 elimination reaction of OH' with both 1 and 2. B) (S‘points) Which of these stereoisomers (1 or 2) has the faster rate of E2 elimination? A) k “M ’5 Ngifl E W H 61D fluTl ’ZI- Pvt .M 612’ (Mud/c é—A WV» , M H , 5’ (gm points) The following bicyclic molecule undergoes an unusual, but well known, rearrangement during solvolysis. Give a detailed mechanism that accounts for the formation of the product. Here are several hints to help you solve the problem: The mechanism occurs in three steps (think about each step): {’S’points) carbocation formation (/opoints) alkyl group migration (it will help to erase the bond that shifts and reconnect it to the new position in a drawing that keeps the same perspective as the starting compound. You can then re-draw the perspective after you make the shift.) EtOH Br —> / H3C heat H3C (s’points) elimination Lib ”a 4% + 5F”; cit; 03 (Ed/92 '7‘ 724’ 3 13ml '2‘ WA 5’ ...
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