Chemistry 21 – Fall 2013 – EXAM 1
Mrs. Nichols
Name:
1. Answer the questions about the following molecule.
O
A
C
O
H2N
B
a. (2 pts) Identify the functional group marked “A.”
b. (4 pts) Identify the orbitals (s, p, sp, sp2, sp3) involved in the σ and π bonds marked “A.”
σ:
π:
c. (2 pts) Estimate the bond angle marked “B.”
d. (2 pts) Identify the electron geometry around the carbon atom marked “C.”
2.
(12 pts, 6 pts ea.) Draw the first molecule, and give the IUPAC name for the second molecule.
a. 6-(4-chloro-1-ethylbutyl)-3-methylundecane
b.
Br
3. Consider the acid-base reaction below.
O
O
O
H
+
S
H
a. (8 pts) Draw the curved arrow mechanism for the reaction, and show all products of the reaction.
b. (2 pts) Of the two bases present at equilibrium, which would have a higher concentration?
(Briefly show your work for full credit).
H2CO3 (pKa 6.35); H2S (pKa 7.0); NaHCO3 (pKa 10.2); CH3SH (pKa 10.5); H2O (pKa 15.7)
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4. (6 pts) Molecule A has a higher boiling point than molecule B. Explain.
OH
A
B
5. (6 pts) Explain in detail why pentane is insoluble in water, including an analysis of the changes in
enthalpy and/or entropy.
6. Chair question:
I
O
a. (8 pts) Draw the other chair conformation and identify which chair is lower in energy. (A values
are I: 0.46 kcal/mol; isopropyl: 2.15 kcal/mol).
b. (2 pts) Is the molecule cis or trans?
7. (6 pts) Which is more acidic, H2S or H2Se? Explain in detail.
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8. Draw the following:
a. (6 pts) The Lewis structure and line structure for this molecule.
ClCH2CH2C(CH3)2CH(CH2OH)CH=CH2
b. (5 pts) The gauche conformation of this molecule, looking down the C3-C4 bond.
O
1
2
3
4
5
6
c. (3 pts) A hydrocarbon that has only 1o and 3o carbon atoms.
d. (6 pts) All resonance structures of this ion, along with the resonance hybrid (making obvious
differences in partial charge).
H
H
N
C
H
C
H
C
H
H
9. (6 pts) Use two reasons to explain why cyclobutane has a large amount of “ring strain.”
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10. (6 pts) Rank the following from least to most water soluble, and explain your answer.
HO
H
O
NH2
O
11. (8 pts, 2 ea.) Multiple choice: circle the correct choice.
a. Which molecule should release the most heat upon full combustion?
A
B
D
C
b. What is the correct order of bond length?
C
O
A.
B.
C.
D.
Short to long:
Short to long:
Short to long:
Short to long:
A<B<C
A<B=C
C<B=A
C=B<A
O
O
A
CH3
B
c. What is the relationship between these two molecules?
OH
A.
B.
C.
D.
They are identical.
They are constitutional isomers.
They are stereoisomers.
They are not isomers.
HO
OH
HO
d. Sulfuric acid (H2SO4) is diprotic and therefore has two pKa’s. What is the relative size of the two
pKa’s?
A.
B.
C.
D.
The pKa’s are the same.
pKa1 is smaller than pKa2.
pKa2 is smaller than pKa1.
There is not enough information.
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