1. No category

CHEMISTRY 211
PRACTICE EXAM II – ANSWER KEY
1) Give IUPAC names to the following compounds.
I
F
F
H3C
Br
CH3
Cl
CH2CH3
CH3CI2CH2CH2
CH2CH3
I
CH3
(5R,6R)-6-chloro-5-ethyl-2,2,5,6-tetraiodooctane
(S)-4-bromo-1,1-difluoro-2,2,4-trimethylcyclopentane
2) Draw accurate structural formulas for the following molecules (next to the name).
a) cis-1-fluoro-3-iodocyclopentane (both enantiomers)
H
F
H
H
H
I
I
F
b) both diastereomers of the structural formulas drawn in 2a
H
I
I
F
H
H
H
F
c) methylene fluoride
CH2F2
d) (3S,4R)-3,4-dibromo-1,6-dichlorohexane (Fischer Projection)
CH2CH2 Cl
H
Br
H
Br
CH2CH2 Cl
e) a diastereomer of structural formula 2d (Fischer Projection)
CH2CH2 Cl
Br
H
H
Br
CH2CH2 Cl
f) the enantiomer of structural formula 2e (Fischer Projection)
CH2CH2 Cl
H
Br
Br
H
CH2CH2 Cl
3) Indicate whether the following pairs of structural formulas represent structural isomers,
stereoisomers or the same molecule. If stereoisomers, classify each pair as
conformational or configurational and as enantiomers or diastereomers. In addition,
label each compound as chiral or achiral and if appropriate, as cis, trans or meso.
H
CH2OH
H
H 3C
OH
OH
CH3
chiral
chiral
NH2
NH2
H
H
NH2
H
H
I
I
H
H
H
H
I
I
cis
achiral
meso
Conformational
Diastereomers
cis
achiral
meso
OH
H
H
H
HO
OH
H
Identical
NH2
trans
achiral
HO
Configurational
Enantiomers
CH2OH
trans
chiral
Structural
Isomers
trans
achiral
H
H
H
Br
Br
Conformational
Enantiomers
H
Br
Br
cis
chiral
cis
chiral
CH2SH
CH2SH
F
H
H
F
F
H
F
H
CH2SH
achiral
meso
CH2SH
chiral
Configurational
Diastereomers
4) Write stepwise, reasonable complete mechanisms for the following transformations. Use
curved arrows to indicate the bonding changes taking place. Predict and/or rationalize the
formation of the major product. Include stereochemistry where indicated.
Cl
CH3
CH CH
OH
H2O
CH3
∆
OH
+ CH3 CH2
CH CH
C
+ HCl
H
O H
H
O H
+
H
O H
Cl
CH3 CH
H3O
+
CH3 CH
CH
CH3 CH
CH
OH
CH3 CH
CH
CH
H
H
O H
H
CH3 CH
H
C
2o R+
O H
H
CH3 CH
C
+
+
H
H
CH3 CH
H3O
O H
H
CH3 CH
C
OH
C
3o R+
CH3CH2CH2
CH(CH3)2
+ CH3O
(E2)
? + CH3OH + I
I
CH3
HOCH3
OCH3
+
H
CH3CH2CH2
H
CH3
H
CH(CH3)2
H
H
I
CH3CH2CH2
CH(CH3)2
CH3
H
CH3CH2CH2
CH(CH3)2
CH3
+
I
4) continued....................
CH2CH3
CH3 C CH2 Br
CH3 C
∆
CH3
CH2CH3
CH2CH3
CH3CH2 OH
CH CH3
+ CH3 C CH2 CH3
+ HBr
OCH2 CH3
Major
SN1 Faster:
CH2CH3
CH3
C CH2
Br
+ Br
CH2CH3
CH3
CH3
C CH2
CH3
CH2CH3
CH3
CH3
C CH2
3o R +
O
O
CH3
C CH2 CH3
OCH2CH3
+
H
CH2CH3
H O
O
CH2CH3
H
H
E1 Slower:
CH2CH3
C
CH3
CH2CH3
H
CH3
CH2CH3
CH2CH3
CH CH3
CH3
C
CH CH3
H O
+
H
CH2CH3
H
O
CH2CH3
H
CH3
H 3C
+ NH3(aq)
Cl
(E1 Only)
? + ? + ? + NH4Cl(aq)
Major
NH3
CH3
H
H3C
CH3
CH3
H3C
H3C
Cl
+
NH4
+ Cl
Major
(tetrasubstd'; most stable; fastest formed)
CH3
H 3C
H
CH3
H3C
NH4
+
H
NH3
H
H
C
CH3
CH3
H2C
+
H
NH3
NH4
CH2CH3
5) Draw accurate stereochemical formulas (Fischer projections or dash-wedge formulas) for
the products obtained in the following reactions. Label each separable fraction as optically
active or inactive. More than one product may be possible.
CH(CH3)2
CH(CH3) 2
CH3
Cl
CH3
SCH3
CH3SH
CH3
(SN1)
CH3
CH(CH3)2
SCH 3
+ CH3S
CH3
SCH 3
CH(CH3)2
CH(CH3) 2
H
CH3CH2O
H
(E2)
CH3
C(CH3)3
CH3CH 2
opt. inact.
(achiral)
F
F
C
opt. act.
H
C(CH3 )3
H
SCH 3
CH(CH3)2
opt. inact.
(meso)
Br
CH3CH2
CH3
NH2
I
H2N
C
(SN2)
H
opt. act.
CH3
6) Circle the one which:
a) is the best choice of substrate and conditions which favor an SN1 reaction.
CH3NH2
∆
CH3
CH3
Cl C
CH3 C
CH2CH3
CH2CH2 Cl
CH3NH2
∆
CH3
CH3
b) are the compounds which would require resolution to separate all of their possible
configurational stereoisomers (more than one answer possible).
isopropyl fluoride
bromoform
1,2-dibromocyclopropane
t-butyl iodide
isobutyl chloride
1,3-dichlorocyclobutane
sec-butyl fluoride
1,4-diiodocyclohexane
c) is the correct order of nucleophiles or bases favoring increasing rate of reactions whose
kinetics would exhibit first-order dependence on the concentration of the alkyl halide
substrate [R-X] only.
H2Se
1
4<2<1<5<3
H2As2
3<5<1<2<4
H2O
3
3<5<1<4<2
HSe4
2<4<1<5<3
H2S
5
2<3<1<5<4
4<5<1<3<2
6) continued..............
d) is the best choice of substrate and conditions which favor an E2 reaction.
I
Br
Br
DMF
CH3
t-BuO
DMF
CH3
e) is the pair of compounds which would be produced in equal amounts by an optically inactive
reaction mixture.
CHO
H
OH & HO
CH3
CH3
CH3
CH3
H
H
H
CHO
OH
OH
&
HO
H
H
I
H
Br
&
OH
H
CH3
CH3
I
I
H
H
Br
H
Br
Br
H
I
Br
H
Br
Br
H
H
&
&
Br
H
H
H
f) is the best choice of substrate and conditions for a bimolecular substitution reaction whose
mechanism is a one-step concerted process.
PH2
MeCN
CH3CH2 CH2 Br
CH3 Br
(CH3)2P
Me2CO
g) is a geminal dihalide with three possible stereoisomers, one of which would exhibit no net
rotation of plane-polarized light.
Cl
H3C
Cl
Cl
F
Cl
F
F
F
H3C
CH3
CH3
F
F
H3C
CH3
Cl
CH3
CH3
Cl
Cl
h) is the correct order of decreasing rate of substrate reactivity for substitution reactions whose
transition state for the rate-determining step (RDS) involves two molecules.
CH3
CH2 Br
1
3>4>2>5>1
CH2 I
Br
3
2
1>5>2>4>3
4>1>2>5>3
CH3
CH3
Br
F
4
3>5>2>1>4
5
4>2>5>1>3
i) is the best choice of substrate and conditions which favor an E1 reaction.
Cl
Cl
OH
OH
DMSO
H2O
3>1>5>2>4
6) continued..............
j) are characteristics of a first-order elimination (E1) reaction (more than one possible).
inversion
second-order rate law
bimolecular reaction
rearrangement
stereospecificity
base-independent rate
anti-coplanar conformation
unimolecular reaction
stepwise process
concerted process
carbocation (R+) intermediates
k) is an achiral object.
human’s hand
eagle's wing
pig's tail
horse’s ass
gorilla's foot