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Chemistry 306, Test #2B (100 points total). Score:______of 100.
Name (Last, First): _________________________P # : _______________ Major : _______________
Please, write and draw in legible manner, use short and clear sentences. Note: the answer we cannot read/understand will be considered wrong!
1. Theory: Explain the nature of interaction of ether and organometallic reagent. Use phenylmagnesium chloride (Ph-
Mg-Cl) and diethylether to illustrate your explanation. You must draw, indicate the formal charges, identify Lewis acid
and Lewis base and give (very) brief written explanation.
Ether: unshared electron pair on oxygen acts as Lewis base capable of stabilizing the lectrodeficient magnesium dication. The dication acts as Lewis acid.
Mg Cl
O
Et (^) Et
O
Et Et
(_____of 10 points)
2. Compare the following nucleophiles. Use the signs < and > to indicate, which one is a stronger nucleophile.
Example A > B means A is a stronger (or better) nucleophile than B.
< or >
< or >
< or >
< or >
< or >
< or >
< or >
< or >
< or >
< or >
N
PPh 3
SH NH 3 H^2 O
NPh 3
OH
CH 3 COOH CH 3 COO
I Br
F H^2 O
S2- HO
NH 3
CH 3 COO^ S
CH 3 OH
(_____of 10 points)
The phenoxide anion is more effectively delocalized in 4-nitrophenoxide anion, which makes this anion more stable and the corresponding conjugated acid (4-nitrophenol) more acidic.
O
NO 2
H
H +
O
NO 2
O
NO 2
O
N O O
O
N O O
O
N O O
O
NO (^2)
O
NO 2
O
H
H +
O O^ O O (^) O
O 2 N O^2 N^ O^2 N^ O^2 N^ O^2 N^ O^2 N
3. Resonance drawing. Give an explanation for why is m -nitrophenol more/less acidic than p -nitrophenol. NOTE:
Explanation that does not show all the different numbers of canonical forms is not sufficient / correct. Include one or
two sentences of verbal explanation to accompany the drawings. Maximum of 1 point for the verbal explanation. Hint :
higher acidity means a more stable corresponding conjugate base.
(_____of 20 points)
6. Write names (structures) for the following structures (names). NO R/S or E/Z required. (_____of 10 pts)
OH Cyclohex-2-enol or 2-cyclohexenol
3,4-dimethoxyphenol OH
H 3 CO
H 3 CO
OH
F
F 2,3-Difluoro-2-buten-1-ol or 2,3-Difluorobut-2-en-1-ol
3-cyclohexenyl phenyl ether O
NO (^2) OH (^) o -Nitrobenzyl alcohol or 2-Nitrobenzyl alcohol
O 2 N OH m -nitrophenol or 3- nitrophenol
7. Fischer and Zig-Zag. Draw the following compound: (_____of 0/5/10 points)
Draw the compound on the left in Fischer projection:
Draw the opposite enantiomer using Zig- Zag representation (to include dash/wedge symbols). Draw the molecule in such a way that it has hydroxy-group on the left and – COOH group on the right side
HO O
F
OH
F
OH OH
COOH
F H
HO H
H CH (^3)
H OH F H
CH 2 OH
HO O
F
OH
F
OH OH
8. Chirality-Representations-Projections. (_____of 10 points)
Consider the following carboxylic acid. A) Find all chiral (stereogenic) centers and assign stereodescriptors for each chiral center (R/S).
HOOC
OH
Cl
highlighted bond
B) Draw the sawhorse projection of this molecule (HOOC in the left upper corner):
C) Draw its Newman projection (use the highlighted bond as the axis of the projection; in such a way that COOH is on the C- atom close to you):
H
OH
COOH
H
Cl
Et
Et
Cl H
COOH
H OH
D) Draw the Fischer projection of this molecule: D) Draw the Fischer projection of the opposite enantiomer:
COOH
H OH
H Cl
Et
COOH
HO H
Cl H
Et
E) Draw the “normal” Zig-Zag formula (like the one on top) of the opposite enantiomer (COOH in the left upper corner):
HOOC
OH
Cl
Bonus question : Consider the structure of 3,4-dimethoxyhexane. Draw all 3,4-dimethoxyhexane isomers in Fischer
projection, indicate: A) whether each compound is chiral or not, and B) their mutual relationship.
H 3 CO H
H 3 CO H
CH 2 CH 3
CH 2 CH 3
H 3 CO H
H OCH 3
CH 2 CH 3
CH 2 CH 3
H OCH 3
H 3 CO H
CH 2 CH 3
CH 2 CH 3
meso -form enantiomers
diastereomers
achiral chiral chiral
(_____of 10 points)
