ALL 2018 CEM 251: rganic Chemistry Sections 25-36 TUE-TU 8:00 9:20 AM September 25, 2018 Name: Section: PD: TA: This is a closed book and note examination. f boxes are provided for your answers, only what is written in the boxes will be graded. You have 80 min to complete the test. Section 25 Thu 10:20 11:10 AM Shuyao Section 26 Thu 10:20 11:10 AM Dan Section 27 Mon 12:40 1:30 PM Dan Section 28 Mon 9:10 10:00 AM Dan Section 29 Tue 10:20 11:10 AM Niloofar Section 30 Thu 1:50 2:40 PM Shuyao Section 31 Thu 4:10 5:00 PM Shuyao Section 32 Tue 3:00 3:50 PM Niloofar Section 33 Tue 4:10 5:00 PM Niloofar Section 34 Thu 4:10 5:00 PM Shuang Section 35 Thu 3:00 3:50 PM Shuang Section 36 Thu 1:50 2:40 PM Shuang Question Points Score 1 12 2 12 3 8+2 4 16+2 5 4 6 13 7 16+4 8 19 Bonus 2 Total 100 (Max) 1
1. Provide a name or a structure for the following compounds (12 pts, 3 pts each box). a. (1S,4R) 1-chloro-4-ethylcycloheptane b. (3S,5S)-5-bromo-3-chloro-5-ethyloctane Br c. (3E) 3,4-dimethylhept-3-ene d. (1R,4R)-1-ethyl-4-methylcycloheptane 2
2. Please determine the chirality (R/S) at the chiral center or stereochemistry (E/Z) at the double bond of the following compounds (12 pts, 3 pt/box) N Br N 2 Z Z R R 3. Please determine the relationship of the following pair of compounds (8 pts, 2 pt / box). Circle the Meso compound(s) (2 pts) Vs enantiomer 2 C N 2 Vs 2 N 2 C identical Vs constitutional isomer N 2 C 2 Vs 2 N C 2 enantiomer 3
4. Please draw the reaction coordinate diagram of the following reaction based on the provided information. Please also indicate the reactant (R), transition state (TS), intermediate (), product (P), ΔG and activation energy (Ea) in the reaction coordinate diagram. (16 pts, 2 pts per box) AB C + D i) 2-step reaction ii) Exogonic reaction iii) 1st step is a rate determining step Energy Reaction Coordinate Please indicate whether the entropy of the following reaction is increase or decrease. (2 pts) 4
5. Please circle the faster reaction of the following pair of reactions (4 pts, 2 pts per question) A. + NaS S + Na Ethanol + NaS S + Na Ethanol B. + LiN 2 N 2 + DMS Li + Li + DMS Li 6 a) Please arrange the nucleophilicity of the following nucleophile from the most nucleophilic to the least nucleophilic (8 pts, 2 pts per box) 2 2 S Most Nucleophilic > > 2 S > 2 Least Nucleophilic 6 b) Please determine whether the indicated atom or bond is nucleophilic (Nuc) or electrophilic (Elc) (5 pts, 1 pts per box) Nuc Li Elc Nuc Nuc Nuc 5
7. Please draw the reaction mechanism of the following reactions (16 pts, 2 pts per arrow). ndicate the reaction mechanism (SN1 or SN2) for each reaction (4 pts, 2 pts per box) A. Li N 2 + + Li + N 3 SN2 B. + + + + SN1 6
8. Please fill in the starting material, reagent or product of the following reactions (16 pts, 2 pts per box). What kind of mixture was generated in Question 8B. (1pt) Please circle two minor products in Question 8C. (2 pts total, 1 pt each) A. Na Br + + NaBr B. + NaCN Methanol CN + CN + Na racemic What kind of mixture has been synthesized from the above reaction (1 pts)? C. + NaS Ethanol S + S + Na S S Please circle two minor products (2 pts total, 1 pt per answer) + D. Br + Na DMS + NaBr 7
Bonus question: Please explain what simple sentence (2 pts) Br in below picture did wrong in one Reference: https://cen.acs.org/sections/sketch-chemistry.html Benzyl bromide acted a SN1 mechanism instead of SN2 mechanism 8
Scratch Sheet: Needs to be turned in with the test (if missing, the test will not be graded) 9
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