Chemistry 211
Exam 2
Fall
Linda Waldman
Name_________________________
Last, First
1) Counting this cover sheet, there are a total of 8 pages- check to ensure you have all 8.
2) All 8 pages must be turned in for grading.
3) Use the backside of preceding pages for scratch paper.
4) Any cheating will result in the dismissal from class with an "F" grade.
5) Please put your name or initial on each page
6) You must sign below to receive a grade on this exam.
I have read and understand the above instructions for this exam.
Signature___________________________________
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Cover page
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Linda Waldman Chemistry 211 F'07
Name________________________
A. (30 points) (2 points each) Multiple Choice. Please write your answers in the spaces provided.
1. A mass spectral analysis was run on an unknown compound and the two observed peaks as
the molecular ions was found to have two equal sized peaks at 276 and 278. From the
1
observed ratio of peaks which halogen in most likely present in this compound?
A) F
B) Cl
C) Br
D) I
2. How many units of unsaturation are indicated by the following molecular formula: C17H18BrI2O2N?
A) 0
B) 6
C) 7 D) 8
E) 9
2
3. The greatest strength of infrared spectroscopy is in determining:
A) the degree of unsaturation
B) the relationships of structural fragments
C) the functional groups present
D) the overall structure of the molecule
E) if rings are present
4. UV-visible spectroscopy involves what type of phenomenon?
A) bending of chemical bonds
B) electron transitions between orbitals
C) molecular rotations
D) nuclear spin transitions
E) stretching of chemical bonds
3
4
5
5. In nuclear magnetic resonance, stronger magnetic fields
B) give different chemical shifts (in ppm) than would weaker magnets.
D) give different coupling constants than would be observed with weaker magnetic fields.
C) give better separation between peaks in the spectrum (in Hz) than would weaker magnets.
6. The most downfield proton NMR signal (i.e., signal most to the left in the spectrum) in the
following molecule would be
A
6
CH 3
Br
H 3C C CH 2 C CH3
Br
B
D
Br
C
E) there is no way to tell
7. How many different types of hydrogens are present in the following molecule?
A) 3
Br
Br
B) 4
C) 5
H3 C CH CH CH CH3
D) 6
E) 7
Br
2
7
Linda Waldman Chemistry 211 F'07
Name________________________
8. What structure of formula C3H6Br2 would give the following proton NMR spectrum?
Br
BrCH2 C CH3
H
A
Br
H3 C C CH 3
Br
C
H
Br2CH C CH 3
H
B
None of these
H
BrCH 2 C CH 2Br
H
D
8
E
9. The CH2 group indicated would most likely appear as what in the proton NMR spectrum?
CH 2 CH 2 OH
9
what will this CH2 appear as?
A) doublet of triplets
B) doublet
C) triplet
D) quartet
E) quintet
10. Consider the 1H-NMR of the molecule shown below. Assume that JCB = 7 Hz and JCA = 1Hz.
What coupling pattern will Hc exhibit?
HB
A) triplet
10
HB
B) quartet
O
C) quintet
CH3
HC
D) triplet of quartets
E) quartet of triplets
HA
HA
HA
1
11. A compound of the formula C10H14 gave an H NMR spectrum that shows two singlets at 6.9 and
2.1. This compound also exhibits three peaks in the 13C NMR spectrum. What compound is it?
CH3
CH3
CH 3
CH3
CH 3
H3 C
CH3
CH3
CH3
CH3
CH3 11
H3 C
CH3
CH 3
H3 C
H3 C
CH3
A)
B)
C)
D)
12. Which of the above structures would show five signals in decoupled
3
CH 3
13
C NMR?
E)
12
Linda Waldman Chemistry 211 F'07
Name________________________
13. Deduce the correct structure: The molecular formula and 13C NMR data (in ppm) are given
below. The splitting pattern of each signal, taken from the non-decoupled spectrum is given
in parentheses.
13
C4H6O: 18.2 (q), 134.9 (d), 153.7 (d), 193.4 (d)
O
O
O
H
A
O
O
H
B
C
D
E
14. In a carbon radical, the single unpaired electron resides in:
A) sp2 orbital.
B) sp3 orbital. C) s orbital.
D) p orbital E)None of these.
14
15. Given the relative reactivities of various kinds of hydrogens, what is the major product of the
following reaction?
15
light
+
Br2
?
Br
Br
no reaction
occurs
Br
Br
Br
A
B
C
D
E
B. (4points) Write the correct IUPAC name for the following compound. (Ignore stereochemistry.)
OH
OH
____________________________________
C. (6 points) What reactants and conditions are required to produce 1-chloro-2,2-dimethylpropane?
Alkane:
Halogen:
Conditions:
+
4
Linda Waldman Chemistry 211 F'07
Name________________________
D. (17 points) Answer the following short answer problems as required.
1. (3 points) Calculate the chemical shift of a peak that occurs 723.2 Hz downfield of TMS on a
spectrum recorded using a 200 MHz spectrometer? (Show your work.)
2. (4 points) The proton chemical shift of methyl fluoride is 4.26 and methyl iodide is 2.16. Explain
the difference in chemical shift.
3. (4 points) Below is the 1H NMR of ethanol and the same sample after 1 mL of D 2O has been
added. Briefly explain what caused the difference in two spectra.
3
2
PPM
1
0
3
2
PPM
1
0
4. (6 points) Briefly describe the factors that affect the stability of tertiary carbocations over primary
carbocations. (For example: Resonance is able to stabilize allylic cations by spreading the
positive charge to other atoms, thereby reducing the effective charge at any given position.)
5
Linda Waldman Chemistry 211 F'07
Name________________________
E. (8 points) What are the relative percents of the monohalogenated products of the reaction
between 3-methylpentane and Cl2 at 20ºC. The relative rates of reaction for chlorination at
this temperature are 1: 5 : 15 for 1º , 2º and 3º carbons respectively. Show all your work.
%
Name of compound
F.
(12 points) Draw the mechanism for the propagation steps for the free radical bromination of
ethane. Be sure to use the correct arrow and show electrons and charges.
6
Linda Waldman Chemistry 211 F'07
Name________________________
G. (10 points) A compound (C4H8O2) exhibits the following IR and proton NMR. Identify the
compound.
The compound with labels is:
IHD =
IR data
ppm
A
4.1
B
2.0
C
1.2
integration
# of H’s
multiplicity
7
Neighbor
H’s
Draw and circle the
hydrogen and neighbor
groups
Linda Waldman Chemistry 211 F'07
Name________________________
1
H. (6 points) Draw the predicted H NMR spectrum for isopropyl alcohol (2-propanol). Be sure
to include the number of peaks, approximate chemical shifts, and draw an integration line to
indicate the relative number of hydrogens.
________________________________________________________________________________|
|
|
|
|
|
4
3
ppm
2
1
0
I. (8 points) Draw the compound with the molecular formula C8H8O shown in the13C NMR below.
The compound with
labels is:
200
180
160
140
120
100
PPM
80
60
40
20
0
The IHD is:
ppm
multiplicity
A
30
q
B
127
d
C
128
d
D
133
d
E
137
s
F
200
s
# of H’s
Circle the carbon and show attached groups
8