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Chemistry 232, Midterm II Instructor: Bergdahl
Summer 2013
Name:___________________________________________________ Be prepared to show ID upon request.
**No cellular phones or calculators are allowed during the test**
My laboratory instructor (TA) is (Please circle): David Schmit Urszula Milewicz Tim Montgomery No TA Before you start the exam, make sure that you have 12 problems!!
A very Good Luck For graders only:
Problem: #1_________/6p #2_________/6p #3_________/6p #4_________/15p #5_________/10p #6_________/10p #7_________/6p #8_________/4p #9_________/8p #10________/12p #11________/16p #12________/10p Total:________/109p Max Total:________/100p
Problem 1. Provide IUPAC names for the following organic structures (Include (R)/(S) if
needed) (6p) a) b)
c)
Cl
Cl Br
CH3 CH3
CH3
CH3
Problem 2. Draw line-angle structures for the following compounds. (6p) A) 2,2,4-trichloro-3-fluoropentane
B) (2R, 3R)-2-Fluoro-3-methylpentane
C) Trans-1-isopropyl-3-methyl-cyclohexane
Problem 3. Your task is to prepare styrene by using one of the two following reactions. Which
reaction would be the most successful one in terms of higher yield than the other? Explain your answer! (6p)
Br
Br
KOH
EtOH, heat
(1)
(2)
Styrene
KOH
EtOH, heatStyrene
Problem 4. Provide the major product formed in the following reactions. (15p)
CH3 Cl
CH3 H3C OH
O
CH3CH2OH
H3C O Na
O
H3C
CH3
ClCH3S Na
DMSO
H3CCH3
OH
Na H
Br
H3CCH3
H3C I
H3C
CH3
CH3
O K
THF
Br H2O
a)
b)
c)
d)
e)
f)
Cl
H3CCl
CH3
Problem 5. Indicate the major product formed in each of the following reactions. Consider the correct stereochemistry of the product answers where appropriate. (10p)
Br
Cl
H
H
H3C
CC
H
NaCN
DMF
NaI
Li THF
Br
a)
b)
Acetone
c) H2(g), CH3OH (solvent)
Pd(cat.)
d) 1)
2)
e)
CH3
CH3
Cl
H3C CH3
N
Li+
THF
Problem 6. Draw the two chair conformations for each of the following two compounds A and B. For each compound, one chair conformation is more favored than the other. Which one is it? (Justification needed for full credit) (10p)
CH3
CH3
H3C
Compound A
Cl
OH
Compound B
CH3
Cl
Problem 7. 1-Bromo-bicyclo[2.2.1]heptane is extremely unreactive in either SN2 or SN1 reactions. Provide explanations for this quite natural behavior for this compound. (6p)
Problem 8. The following data is provided for the following two enantiomers of 2-methyl-1-
butanol.
OH
(R)-(+)-2-Methyl-1-butanol
[]D = +6.0 deg
OH
(S)-(-)-2-Methyl-1-butanol
[]D = -6.0 deg
A sample of 2-methyl-1-butanol has an observed specific optical rotation of +4.0 deg. What is the enantiomeric excess (e.e.)? What is the actual ratio, in %, of the enantiomers in the sample? (4p)
Problem 9. Draw the conformational structures (chairs) for the substitution products of the following compounds. (8p)
Cl
CH3
A)MeOH, H2O
Cl
HB)
I
D
H
MeOH
Cl
HMeOH
C)I
D
H
Cl
H MeOH
D) I
D
H
D
H
Problem 10. Shown below are the Newman projection formulas for 2,3-di-chlorobutane. (12p) a) Draw line angle structures for the three structures and determine R and S in these.
Clearly indicate which structure is A, B, and C respectively. b) Which formula A, B, or C is the meso structure?
CH3
Cl H
Cl
CH3
HCH3
H Cl
Cl
CH3
HCH3
Cl H
H
CH3
Cl
A B C
Problem 11. Consider the following pairs of structures. Designate each stereocenter as either (R) or (S) and identify the relationship between them by describing them either as enantiomers, diastereomers, constitutional isomers, or two identical molecules. (16p)
F Br
CH3Hand
H
FClBr
a)
b)
H
H
F
BrCH3
H3C
andBr
CH3H
HCH3
F
c)and
Cl
ClCl
Cl
d)H
CH3
Cl
CH3
H Cl
Cl
CH3
H
CH3
H Cland
e)
CH3
BrH
and
CH3
BrH
Problem 12. A) Circle the most powerful nucleophile for each of the following pairs using polar aprotic solvent. (4p)
(i) CH3NH or CH3NH2
(ii) CH3SH or CH3OH
(iii) HO or CH3COO
(iv) F or Br B) The following SN2 reaction can be conducted in either ethanol or DMF as a solvent, and the rate of this reaction is dependent on which solvent is used. Which solvent, DMF or ethanol, will increase the rate of this SN2 reaction? Explain! (6p)
Br
NaN3
N3solvent
Scratch paper
Scratch paper
Scratch paper
