Chemistry 2423
Exam 2A
O Cimene – refers toseveral isomeric compounds. The Ocimenes
are monoterpenes found within varity of plants fruits.
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ORGANIC CHEM 2423 EXAM # 2A Sample(Chapters 5,6, and7)
Name:__________________
Score
DIRECTIONS- Please answer all questions in the space provided as completely and clearly as possible .
Show all your work for the writing portions of the exam.
PART I – Multiple Choice (3 points each)
____1. Which of the following compounds are chiral?
Cl
Cl
CH3
CH3
I
CH3
II
A. I and II
B. II and III
Cl
Cl
Cl
CH3
III
C. III and IV
CH3
IV
D. IV and V
V
E. All of them
_____ 2. Assign Cahn-Ingold-Prelog rankings to the following compounds.
-CH2F, CHO, -CO2H, -CH2OH
A. CH2F: 1, CH2OH: 2, -CO2H: 3, -CHO: 4
B. CH2F: 1, CH2OH: 3, -CO2H: 2, -CHO: 4
C. CH2F: 3, CH2OH: 4, -CO2H: 1, -CHO: 2
D. CH2F: 4, CH2OH: 3, -CO2H: 2, -CHO: 1
E. CH2F: 4, CH2OH: 2, -CO2H: 1, -CHO: 3
_____ 3. Identify R, S configuration of the chiral centers in D-threose
A, 2S, 3S
B. 2R, 3R
C. 2S, 3R
_____ 4. Identify the correct definition of Diastereomers.
A. They are stereoisomers and mirror images
B. They are not stereoisomers but mirror images
C. They are stereoisomers but not mirror images
D. They do not have optical activity
E. No correct answer
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D. 2R, 3S
E. None of them
_____ 5. Identify the type of the following reaction:
Br
Br2 / H2O
OH
A. elimination
B. substitution
C. addition
D. rearrangement
_____ 6. Consider the following reaction. Which species is the nucleophile?
..
O:
..
..
O:
+
(I)
: CN
CN
( II)
A. I only
( III )
B. II only
C. III only
D. none of these
_____ 7. This process occurs when both bonding electrons remain with one product fragment.
A. homolytic bond breaking
C. hemolytic bond formation
B. heterolytic bond breaking
D. radical formation
_____8. How many degree of unsaturation are in Valium (diazepam) , C6H10O ?
A. 1
B. 2
C. 3
D. 4
_____ 9. Provide the proper IUPAC name for the alkene shown below.
CH3 – CH = CH – CH2 – CH3
A. n- pentane
B. 3-pentene
C. 2- pentene
D. 2- pentyne
_____ 10. What is the acceptable structure for 1,2-dimethylcyclohexene?
A.
D.
C
B.
_____ 11. What two atomic orbitals or hybrid atomic orbitals overlap to form the C = C bond in ethene?
A. sp-sp
B. sp2 – sp2
C. sp-sp2
D. sp3-sp3
_____ 12. Which of the following has the highest priority?
A. –CN
B. –OH
C. - CH3
3
D. – OCH3
_____13. Which of the following alkenes is most stable?
A.
B.
C.
D.
_____14. Provide the reagents necessary to complete the following transformation.
OH
O
CO2
A. KOH /ethanol
+
B. KMnO4 /H3O+
C. CH2I2 /Zn(Cu)
D. none of these
_____15. Bromination of a cycloalkene results:
A. bromonium intermediate
C. trans dibromo compound
B. cis dibromo compound
D. Markovnikov addition
E. A and C
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_____16. In a radical reaction, the following step Cl• + CH3 - CH2 - CH3  CH3 –CH - CH3 + HCl
is an example of______.
A. initiation
B. propagation
C. termination
D. addition
_____17. Addition of HBr to 2-butene is called ___________________.
A. Hydroboration hydration
C. Hydrohalogenation
B. Hydrogenation
D. Hydration
_____18. What is the major of the following reaction?
OH
H2SO4 /heat
CH3
A.
D.
C.
B.
CH2
CH3
4
CH3
____19. Ocimene is a triene found in the essential oils of many plants. What is its IUPAC name, including
stereochemistry?
A) (3Z)-3,7-dimethyl-1,3,6-octatriene
C) (5Z)-2,6-dimethyl-2,5,7-octatriene
B) (3E)-3,7-dimethyl-1,3,6-octatriene
D) (5E)-2,6-dimethyl-2,5,7-octatriene
_____20. Arrange the following carbocations in order of increasing stability (least stable to most stable).
I
A) III < II < I
II
B) I < II < III
C) I < III < II
III
D) II < III < I
PART II – Show your work
1. Naming and structures ( 4 points each)
a) Give the IUPAC name of the following compounds:
I
II
I. _______________________________________
II. _______________________________________
III. ______________________________________
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III
b) Draw structures corresponding to the following systematic names;
(2Z)- 3-methyl-2-pentene
2,3-dimethyl-1-cyclopentene
2. ( 5 points) Show by a series of reactions how could you prepare the following compounds from the
indicated starting compound. Be sure to clearly indicate the reagents used in each step.
Cl
Cl
3. ( 5 points) Propose a mechanism to account for the shown product. Please show the structures of
the intermediates and using curved arrows to indicate electron flow in each step.
(Rearrangement may occur)
CH3
CH3 - C - CH = CH2
ether
+ HBr
CH3
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4. Identify all the enantiomers and diastereomers
5. Propose a mechanism, showing the structures of the intermediates in the following
reaction:
Cl
+
HCl
Bonus Question ( 5 points) – Please show all your work for complete credit.
Write structures of (R)-2-Chlorobutanol and (S)-2-Chlorobutanol
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Key to important questions inPART II
1. Naming and structures
a) I. 3- Methyl-1-cyclohexene II . (3Z) –2,3,4-trimethyl-3-hexene III. 3,7-dimethyl-1,3,6-octatiene
b)
(2Z)- 3-methyl-2-pentene
2,3-dimethyl-1-cyclopentene
H
CH3
CH3
C=C
CH3
CH3-CH2
CH3
2. Show by a series of reactions how could you prepare the following compounds from the
indicated starting compound. Be sure to clearly indicate the reagents used in each step.
Cl
Cl
CHCl3 /KOH
Cl2 /light
Cl
KOH /ethanol
3. Propose a mechanism to account for the following reaction. Please show the structures of
the intermediates and using curved arrows to indicate electron flow in each step.
(Rearrangement may occur)
CH3
CH3
ether
CH3 - C - CH = CH2
+ HBr
CH3
CH3 - C - CH - CH3
methide
shift
:Br
CH3
:Br
CH3 - C - CH - CH3
CH3
CH3
3 carbocation intermediate
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Br
CH3 - C - CH - CH3
CH3
2 carbocation intermediate
CH3
Br
CH3
CH3 - C - CH - CH3
CH3
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