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Midterm_2_Key - Spring 2008 118A Midterm 2 Page 2 Initials...

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Unformatted text preview: Spring 2008 118A Midterm 2 Page 2 Initials 1. ( 12 pts) Name each compound below, using systematic nomenclature. Use proper designators where applicable to indicate absolute stereochemistry. a} (a) ajfi/ (g7-l,ctnovo-g-aa (Amati we c0“ ‘ (b) OH /J\/\(Br WM”— Br 1 / (15 7,3) I Mi 2 its-do 0‘0 «0 we ”W2. (15 pts) Multiple choice. Circle the best answer. as (a) Property of a chiral molecule. must have * identical with diastereomers mirror image displays ( optical activity (b) A chiral carbon may be i cannot be must be sp3 planar in a ring hybridized (Cl lf [0t] for (28,3S)-tartaric acid is —12°, then [0L] for (2R,3R)-tartaric acid is —12° 0° impossible to tell [Tartaric acid is HOzC—CHOH—CHOH—COzH] (d) If [0t] for (ZS,BS)—tartan'c acid is —12°, then [0t] for (2R,3S)-tartaric acid is -120 C0? +12° impossible to tell (e! A sample of tartaric acid showing an [on] of +6° could contain / / 75% R,R 67% R,R 50% R,R 33% R,R ( and 25% 5,5 and 33% 8,8 and 50% 8,8 and 67% 8,3 Spring 2008 118A Midterm 2 Page 3 Initials 3.( 15 pts) )Circle each chiral molecule Put a star (*) next to each chiral carbon ll Md“ . . eWOV 4. (12 ptsi (a) In the box at the right draw a good Cl stereochemical picture of cis—l-chloro—4-ethylcyclo— C H3014 4 +)" f’ hexane in its most stable conformation: (b) Draw the most stable conformation of trans- l —chloro—4-ethylcyclohexane in the next box: (c) Which compound do yozu think is more stable, ,czz's-+or trans— 1 -chloro- 4- ethylcyclohexane? Why? 3 p 9 (Herzl/.3 ., Com lam/e Qa—eL‘ go L gilt/Fmewt 3 87": who well 01+ W 5&1sz +(M I Spring 2008 118A Midterm 2 Page 4 Initials 5. (24 pts} Write the structure(s) of th ma'o organic product(s) of each reaction below to the right of the arrow. Then, write the abbreviation tha escribes the mechanism in the space provided. IF YOU THINK THAT NO REACTION (or only an exceedingly slow reaction) OCCURS, WRITE "NR." Assume all indicated reagents are present in excess. «5(ng F (a) /\/C1 £531.» CH3OH grin/€911. Mechanism (47+ €q SH __§fl_1_ :1 NaSH N R . 7—...— 31/1 SM! E2 (+09 (52,) Spring 2008 118A Midterm 2 Page 5 Initials 6. (8 pts) Write out a complete, step-by-step mechanism for the reaction of (CH3)3CBr and ethanol. Show only the pathway that leads to the major product. rmév \VV \ Q 6p, l + m wt c + WM ~- A. C , o 4W; “‘5 W ”T9 /\ ”A I 5 ‘ ,_ \{Y’ - H B( erg z 5) +5 7. (16 pts) Matching. Which of the four structures below, left, best fits the IR spectrum at the right? Circle your choice? ,1 0 /'fl OH I ©& ~ 7 “J C: OH I 0 on ;\ 8. (8 pts) Multiple choice. Circle the best answer. a) D (a) Strongest acid: CH3OH GH3C02H CH3CONH2 CH3CON(CH3)2 / (b) Best leaving group: CH3O' 'CH3C02‘ HO‘ "\ C1“ > F” \ \\ «a. / ”\t 'I- 0— Ho- H20 CH3OH (c) Best nucleophile in CH3OHIX/V ‘ _, _....__\‘ \> Br / \‘\ (d) Best 3N2 substrate: 3’ Wm) /l\/Br \/‘\ ...
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