fall 2018 cem 251: organic chemistry i sections 25-36 tue … · 2018-12-07 · cem251, fall 2018...
TRANSCRIPT
CEM251, Fall 2018 Midterm #2
1
FALL 2018 CEM 251: Organic Chemistry I
Sections 25-36
TUE-THU 8:00 – 9:20 AM
September 25, 2018
Name:______________________________ PID: _______________________________
Section:____________ TA: _______________
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)
This is a closed book and note examination. If 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
CEM251, Fall 2018 Midterm #2
2
1. Provide a name or a structure for the following compounds (12 pts, 3 pts each box). a. (1R,3R) 1-bromo-3-propylcyclohexane b. c. (3Z) 4-ethyl-3-methylhept-3-ene d.
(3S,5R)-5-chloro-3-iodo-3-methylheptane
(1R,3S)-1-ethyl-3-propylcyclooctane
ICl
Br
CEM251, Fall 2018 Midterm #2
3
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)
3. Please determine the relationship of the following pair of compounds (8 pts, 2 pt / box). Circle the Meso compound(s) (2 pts)
O
NH H OH
I
HOCl
NH2OH
Cl
E Z S S
Vs
Vs
OH
NH2ClHHOHHOH2C
NH2
H
ClOHHOHHOH2C
Vs
Vs
CH2OH
HHOHHONH2H
HCH2OH
HHOHHOCH2OHH2N
CH2OHH2N HNH2
H
Cl Cl
Cl
Cl
F Cl
F
Cl
Cl
Cl
constitutional isomer
enantiomer
diastereoisomer
diastereoisomer
CEM251, Fall 2018 Midterm #2
4
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 (I), product (P), ΔG and activation energy (Ea) in the reaction coordinate diagram. (16 pts, 2 pts per box)
i) 2-step reaction ii) Endogonic reaction iii) 1st step is a rate determining step
Please indicate whether the entropy of the following reaction is increase or decrease. (2 pts) Decrease
A + B C
Energy
Reaction Coordinate
CEM251, Fall 2018 Midterm #2
5
5. Please circle the faster reaction of the following pair of reactions (4 pts, 2 pts per question)
6 a) Please arrange the nucleophilicity of the following nucleophile from the most nucleophilic to the least nucleophilic (8 pts, 2 pts per box)
6 b) Please determine whether the indicated atom or bond is nucleophilic (Nuc) or electrophilic (Elc) (5 pts, 1 pts per box)
F + NaOH OH + NaFEthanol
A.
I + NaOH OH + NaIEthanol
+ +DMSO
B.
+ +DMSO
Cl
Cl
H2O
LiOH
OH
OH
HCl
LiCl
F NH3 Br H2O
MostNucleophilic
LeastNucleophilic> > >Br- F- NH3 H2O
NH
SH Li
Ele
Nuc
Nuc Nuc Nuc
CEM251, Fall 2018 Midterm #2
6
7. Please draw the reaction mechanism of the following reactions (16 pts, 2 pts per arrow). Indicate the reaction mechanism (SN1 or SN2) for each reaction (4 pts, 2 pts per box)
SN1 SN2
OH + H Cl Cl + H2O
A.
HO H Cl
I +H
Li NH2
B.
+ LiI + NH3
I
CEM251, Fall 2018 Midterm #2
7
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 for Question 8C. (2pts total, 1 pts each)
I + NaSH Methanol+ + NaI
Br + O
O
+ NaBr
I + NaCNEthanol
+ + NaI
Please circle two minor products (2 pts total, 1 pt per answer)
+
Cl+ NaI
DMSO+ NaCl
What kind of mixture has been synthesized from the above reaction (1 pts)?
A.
B.
C.
D.
O
O
SH SH
racemic
CN CN
CN CN
I
Na
CEM251, Fall 2018 Midterm #2
8
Bonus question: Please explain what in below picture did wrong in one simple sentence (2 pts)
Reference: https://cen.acs.org/sections/sketch-chemistry.html Benzyl bromide acted a SN1 mechanism instead of a SN2 mechanism
Br
CEM251, Fall 2018 Midterm #2
9
Scratch Sheet: Needs to be turned in with the test (if missing, the test will not be graded)
CEM251, Fall 2018 Midterm #2
10