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SAMPLE ORGANIC CHEM 2423 EXAM #1( Ch. 1-4)
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. How would you best describe the C-C bonds in H3C-CH2-CH3?
A. sp3-sp
B. sp2-sp3
C. sp3-sp3
D. sp-sp
____2. Which of the following molecules contains an sp-hybrized N-atom?
B. NH4+
A. NH3
C. CH3NH2
D. HCN
____3. Which of the following statement is(are) correct?
A. the maximum number of electrons possible for a set of p-orbitals is 6?
B. the ground state electron configuration of carbon 1s2 2s2 2px1 2py1 2pz0 .
C. the total number of bonding electron pairs in BF3 is 3.
D. All of these
____4. What is the formal charge on the N-atom in nitromethane, CH3NO2, in the
most important resonance forms of this molecule?
B. –2
A. +1
C. –1
D. +2
____5.Which one of the following notations does not represent an acceptable
condensed structural formula of propanol, C3H8O?
A. CH3-CH2-CH2OH
C. CH3-CH2-CH2-O-H
B. CH3-CH2-CH2-OH
D. CH3CH2CH2OH
____6. Which is the correct order of increasing bond polarity? (Consider the
electronegativities of the halogens.)
A. H-F < H-Cl > H-Br > H-I
C. H-F > H-Cl < H-Br < H-I
B. H-F < H-Cl < H-Br < H-I
D. HI < H-Br < H-Cl <H-F
____ 7. Which of the following conformation is the most stable conformation of butane, view the
molecule from the central carbons?
CH3
H
H
H
A. I only
H
CH3
CH3
H
H
H
CH3
H
H
CH3
CH3
H
H
I
II
III
B. II only
C. III only
H
D. all of these
____ 8. Which of the following cyclohexane conformation is(are) consider to be cis
conformation?
A. I only
III
II
I
B. II only
C. I and II
D. I, II, and III
____ 9. What is the IUPAC name of neopentane?
A. 2-methyl-butane
C. 1,1-dimethylpropane
B. 3-methyl-butane
D. 2,2-dimethylpropane
____10. Which structure is tert.-butyl bromide?
A. Br-CH(CH3)-CH2-CH3
C. Br-CH2-CH(CH3)2
B. Br-C(CH3)3
D. Br-C(CH3)2-CH2-CH3
____11. Which one of the alkanes would you suspect to have the lowest boiling point?
A. 2-methylpropane
B. pentane
C. nonane
D. butane
____ 12. Which reaction describes the complete combustion of propane?
A.
B.
C.
D.
C3H8 + 5 O2
C3H8 + 3 O2
C3H8 + 3.5 O2
C3H8 + 4.5 O2
3 CO2 + 4 H2O
3 CO2 + 3 H2O
3 CO + 4 H2O
3 CO2 + 3 H2O
____13. Which conformation of cyclohexane corresponds to the most stable
structure?
A. half chair
B. chair
C. twist-chair
D. none of these
____14. Name the compound CH3-C(CH3)2-CClH-CH3 according to IUPAC
nomenclature.
A. 3-chloro-1,2-dimethylbutane
C. 3-chloro-2,2-diethylbutane
B. 3-chloro-2,2-dimethylbutane
D. 2-chloro-3,3-dimethylbutane
____15.What is the barrier to rotation about the C-C bond in ethane?
A. about 1.0 kcal/mol
C. about 2.0 kcal/mol
B. about 3.0 kcal/mol
D. about 2.5 kcal/mol
____16. An axial methyl group in cyclohexane suffers from what disadvantage?
A. one 1,3-diaxial interactions
C. two 1,3-diaxial interactions
B. two 1,2-diaxial interactions
D. one 1,2-diaxial interactions
____17. Among the following pairs of isomers, identify the pair of constitutional
isomers.
A. neopentane and isopentane
B. isobutane and 2-methylpentane
C. neopentane and isobutane
D. isopentane and 2,2-dimethylbutane
____18. How many tertiary hydrogen atoms are there in Cl-CH2-C(CH3)2-CH(CH3)-C(CH3)3?
A. 6
B.3
C. 2
D. 1
____19. Consider the structure of trans-1,4-dimethylcyclohexane. Which statement
is fully correct?
A.
B.
C.
D.
Trans methyl groups favor chair and both are equatorial.
Trans methyl groups favor chair and both are axial.
Trans methyl groups favor twist-boat conformation.
Trans methyl groups favor chair and are axial and equatorial.
____20. Which statement is written incorrectly?
A.
B.
C.
D.
Acetic acid (pKa =4.73) is stronger acid than water(pKa =15.75).
The conjugate acid to (CH3)3N: is (CH3)3NH+.
An electron pair donor substance considers being a Lewis acid.
The stronger the acid, the weaker the conjugate base.
PART II- Show your work (8 points each)
21. Naming and Structures
CH3CH2
_______________________________
cis- 1-ethyl-3-methylcyclohexane
CH3
__________________________________
5-ethyl-4-isopropyldecane
22. Draw all the possible resonances (at least two) for the following compound:
CH3
..
23. Identify the functional groups in the following compound and name each functional group.
CO - O - CH2 -CH3
O - CH = CH3
24. Complete the following reactions and write the major products.
a) CH3 - CH2 - CH - CH3 +
O2
CH3
+
b)
Cl2 / light
CH3
c)
+
O2
+
d)
Cl2 /light
25. Given that Ka for HCN is 4.9x10 –10 and Ka for water 1.80x10-16, will the following reaction
occur? (will the products be favored at equilibrium?). Please explain for complete credit.
HCN + OH-
?
CN - + H2O
BONUS Question(10 points)- Show all your work.
Please draw five isomers (constitutional or/and geometrical) of cyclobutane derivatives of the
formula C5H9Cl. Please name each isomer.
ORGANIC CHEM 2423 EXAM #1 ( Answers)
1. C 2. D 3. D 4. A 5. C 6. D 7. A 8. A 9. D 10. B
11. A 12. A 13. B 14. B 15. B 16. C 17. A 18. D 19. A 20. C
trans –1-ethyl-3- methylcyclohexane
21. Naming: 3,4-diethyloctane
Structures :
CH2CH3
CH3
22.
CH3
CH3
CH3
..
..
..
23.
CO - O - CH2 - CH3
ester
alkene
O - CH = CH2
ether
aromatic
24.
a) CH3 - CH2 - CH - CH3 + 8 O2
5 CO2 + 6 H2O
CH3
+ HCl
+ Cl2 /light
b)
CH3
CH3
Cl
c)
d)
+ 6 O2
4 CO2
+ 4 H2O
+ Cl2 /light
Cl
25. K = Ka (reactant acid) / Ka(product acid) = (4.9x10 -10)/(1.80x110 -16) = 2.72x106 > 1.0
products will be favored ()
Cl
Cl
CH3
CH3
cis-1-chloro-2-methylcyclobutane
1-chloro-1-methylcyclobutane
CH3
CH3
trans-1-chloro-2-methylcyclobutane
Cl
Cl
CH3
cis -1-chloro-3-methylcyclobutane
Cl
trans-1-chloro-3-methylcyclobutane