Chemistry 110a
FIRST EXAM
September 21, 2007
Name (print)______________________________
Actor and 2008 presidential hopeful Christopher Walken made TV history when, appearing as
rock & roll producer Bruce Dickinson in a Saturday Night Live parody of a Blue Öyster Cult
recording session of (Don’t Fear) The Reaper, he uttered the following exhortation to the band:
I gotta have more __________________________, baby!
A. electric guitar
B. Moog synthesizer
C. cowbell
D. timbal
Note: Your exam should consist of 5 pages including the cover page and grade tabulation sheet.
Skim the entire exam and solve the easiest problems first. Exams not returned at the end of the
period will not be graded.
A helpful hint: On organic exams, a well-crafted & annotated structure can speak volumes.
Sentences here and there are OK. Paragraphs, on the other hand, are generally frowned upon!
There are no essay questions on this exam.
PLEASE DO NOT OPEN THIS EXAM UNTIL YOU
ARE INSTRUCTED TO DO SO.
2
1. Dimethylformamide (DMF), HCON(CH3)2, is an example of a polar aprotic solvent, aprotic meaning that it has no
hydrogen atoms attached to highly electronegative atoms. (a) Using dash-type structural formulas, showing
unshared electron pairs, draw the two best resonance structures for this molecule. (b) Circle the 'more important'
resonance structure, using the rules we learned for evaluating resonance structures. 8 pts
2. (a) Give an example of a polar protic solvent:
use a chemical structure in your answer! 2 pts
(b) Give an example of an apolar aprotic solvent:
use a chemical structure in your answer! 2 pts
3. There are four constitutionally isomeric alkyl chlorides with the formula C4H9Cl. Write their bond-line formulas
and classify each as a primary, secondary, or tertiary alkyl chloride. 12 pts
4. Aspartame is a widely used artificial sweetner. Indeed, according to the SinoSweet web page: "We output 1,200
metric tons of aspartame yearly that is in conformance with FCCIV, USP24, NF-19, and EP2000 stipulations. Our
aspartame tastes pure, is odorless, and is widely used as an additive in instant foods, dietetic products, and
carbonated beverages." Carefully circle and identify five functional groups in Aspartame. 10 pts.
O
HO
O
NH2
N
H
OMe
O
3
5. Use structures employing well-drawn orbitals to explain why the IR carbon-oxygen stretching frequency of ketones
(1720 cm-1) is signficantly higher than carbon-oxygen stretching frequency in ethers (1100 cm-1). Cite and use the
"IR equation" in your answer. 10 pts
6. The dipole moment of formaldehyde (H2CO) is 2.27 D, whereas the dipole moment of carbon monoxide is much
smaller (0.11 D). Use Lewis structures and resonance theory to account for this observation. 10 pts
7. Add charges to non-hydrogen atoms in the following molecules where necessary. 8 pts
Br
N
O
H3C
CH2
S
H2C
CH2
H2C
CH2
H2C
CH2
O
8. Consider the structure of Anisomycin, a protein synthesis inhibitor:
H
H
H
H
N
6 pts
H
a. Draw a circle around the most acidic hydrogen atom
in Anisomycin.
H
HO
O H
OCH3
H
O
Researchers have shown that if an animal is given
anisomycin within a f ew hours of f orming a memory,
the memory disappears. T his evidence supports the
hypothesis that long-term memory f ormation depends
upon protein synthesis.
b. Draw a square around the second-most acidic hydrogen
atom in Anisomycin.
c. At pH 11.0, the amine functional group in anisomycin is
(circle one)
primary
/
secondary
/
tertiary
/
quaternary
4
8. Write a valid Lewis structure for each of the following inorganic compounds. 12 pts
a. amide ion, NH2
b. dinitrogen trioxide (arranged ONONO)
a
c. nitronium ion, NO2+ (arranged ONO)
d. hydrazoic acid, HN3 (arranged HNNN)
b
c
d
9. The pKa for HN3 is 4.7. (a) Explain what this means (write your answer in the box labeled 'a' below). (b) Do you
expect the pKa of cyanic acid (HOCN) to be lower than / equal to / greater than that for hydrazoic acid? (circle
your answer & provide a brief explanation in the box labeled 'b' below). 8 pts
a
10. Using your HN3 Lewis structure as a starting point, re-draw this compound using well-drawn and labeled orbitals
superimposed onto a framework that communicates the three-dimensional shape of this molecule. 8 pts
11. Match the chemist with the commentary by inscribing the correct capital letter in the box. 4 pts
A. Kekule
A. 'I can make urea, without the assistance of a kidney!'
A. S. Couper
B. 'The more I think about it, the proton is overrated--an acid is an electron pair
acceptor.'
F. Wohler
C. 'To me, molecues look a lot like sausages. Pass the mustard!'
G. N. Lewis
D. 'I deserve the credit for bond-line representations...but some old geezers
slowed the publication of my results!'
b
5
Chemistry 110a
FIRST EXAM
September 21, 2007
Name (print)______________________________
Page
Points
2
34
3
34
4
32
Total
100
Score