Chemistry 220
Fall 2002
Exam 1
Choose the one best answer for the next ten questions. (30 pts)
1. Valence electrons refer to those
a. In the nearest shell
b. In the outermost shell
c. Of lowest energy
d. That are electronegative
e. Which are negative
2. Which structures represent isomers?
a.
b.
CH3
c. CH3CH2CHCH2CH3
CH2CH3
CH3CH2CHCH3
d.
D is the correct answer.
3. Which of the following does NOT exhibit a net dipole moment of zero?
a. CO2
b. CH4
c. CCl4
d. H2O
e. SO3
4. Which geometry / hydbridization is incorrect?
a. Linear / sp
b. Trigonal planar / sp2
c. Tetrahedral / sp3
d. All are correct
e. All are incorrect
5. An unknown compound was analyzed using combustion analysis and mass spectroscopy.
Combustion analysis showed the compound has an empirical formula of CH2O. Mass
spectroscopy showed a molecular ion of m/z = 150. What is the molecular formula for this
compound?
a. C10H14O
b. C6H12O6
c. C5H10O5
d. There isn’t enough information to choose between a and c
e. There isn’t enough information to choose between b and c
6. Which of the following structures could represent a conjugate acid?
CH5+1
H2 O
HC≡CH
I
II
III
a.
b.
c.
d.
e.
Only I
I and IV
I, II, and III
II and III
II and IV
7. The eclipsed and staggered forms of butane are said to differ in
a. configuration
b. conformation
c. constitution
d. molecular formula
e. structure
8. The dots in Lewis structures represent
a. All electrons
b. The charge
c. The number of protons
d. Valence electrons
e. None of the above
9. An orbital
a. Describes a volume of space for an electron
b. Is a solution to a wave equation
c. Shows the precise orbit of an electron around an atom
d. A and B
e. A, B, and C
10. Hydrogen bonding can be an example of which interaction(s)
a. Ion-ion
b. Dipole-Dipole
c. Dipole-induced dipole
d. A, B
e. A, B, and C
CH3NH4+2
IV
11. Draw Lewis structures for five isomers of C5H10O. (10 pts)
O
H
H
C
H
C
C
H
H
H
H
C
H
C
H
H
H
C
H
H
C
H
I
O
H
C
H
C
H
H
C
C
H
C
H
C
II
H
H
H
H
C
H
C
H
C
H
H
H
H
H
H
H
H
H
O
C
C
C
C
H
C
H
H
C
H
C
O
H
C
H
H
C
H
H
H
III
H
There are many other
possible structures as
well.
H
O
H
H
H
IV
V
a. Predict the geometry at each carbon for one of your compounds. (5 pts)
tetrahedral
O
H
trigonal planar
b. For each of your structures, indicate how many signals would you expect to find in the 13C
NMR spectrum. (5 pts)
I = 5 signals, one in the 200 ppm range
II = 3 signals
III = 5 signals, two in the 100-150 ppm range
IV = 4 signals, one in the 200 ppm range
V = 5 signals, two in the 100-150 range
12. Geraniol is a terpene obtained from roses. Its condensed formula is:
(CH3)2C=CHCH2CH2C(CH3)=CHCH2OH.
a. How many carbons are in the longest continuous chain in this molecule? (2 pts)
8 carbons
b. What is the hybridization at all of the carbon atoms in this compound? (8 pts)
sp3
OH
sp2
13. Chemists in Australia recently reported isolating the following compound from the air-dried
leaves of Caesalpinia pulcherimma. [see Ragasa, et al. J. Nat. Prod. 2002, 65, 1107-1110.]
Decoctions of the leaves have been used in traditional Philippine remedies for centuries. Label
and name each of the functional groups present in this molecule. (10 pts)
alkene
arene*
O
O
ester
H
ether
H
O
arene
OH
alcohol
arene* - we haven't learned this configuration yet,
and won't until Organic II
14. Provide the IUPAC name or draw the structures for five of the following compounds (20 pts)
a.
b.
Br
1,2-diethyl-3-methylcycloheptane
c. (CH3)2CH2CH(CH3)CH2CH2CH2Br
2-bromo-4-ethyl-2-methyloctane
d. 3-ethyl-1,1-difluoropentane
F
1-bromo-4,5-dimethylhexane
F
e. 1,2-diethylcyclobutane
f. 5-chloro-2,8-dimethyl-4-propyldecane
Cl
15. Draw Newman projections of the different conformations of 2,3-dimethylbutane and indicate
the highest and lowest energy conformations. (10 pts)
CH3
CH3
H
H
CH3
H
CH3
CH3
CH3
H
CH3
CH3
CH
CH3 3
CH3
H
HCH3
highest energy
CH3
CH3
CH3
CH3
H
H
CH3
CH3
CH3
H
H
CH3
CH3
H
CH3
H
CH3
CH3
lowest energy