CHEM 4341/6371 PART A
1. Spectra A-C: Determine the structure of the C 8 H 10 compounds using the provided
spectra.
(a) Based only on SODAR and the presence/absence of benzene rings, draw the
four possible structures.
(b) Provide the structure of the compound that matches each spectrum [you can
determine the structures using the oop bending region of the IR spectrum].
2. Spectra D-G: Determine the structure of the C 9 H 12 compounds using the provided
spectra.
(a) Based only on SODAR and the presence/absence of benzene rings, draw the
eight possible structures.
(b) Provide the structure of the compound that matches each spectrum [you can
determine the structures using the oop bending region and other regions of the
IR spectrum].
3. Spectra H-J: Determine the structure of the following C 9 H 12 O compounds using the
provided spectra.
(a) Ignoring stereochemistry, draw the five possible structures based only on
SODAR, the absence/presence of benzene rings, benzene substitution pattern,
and the presence of functional groups present in all of the compounds.
(b) Refer to the textbook for details on the C-O stretch in relation to the nature of
alcohols. Identify the type of alcohol (e.g., 1°, 2° and 3°) corresponding to each
spectrum.
4. Match compounds 1-4 (all C 7 H 14 O 2 ) to their corresponding IR spectrum.
5. Match the compounds 5-8 (all C 8 H 9 NO 2 ) to their corresponding IR spectrum.
[NOTE: strong electron donating or withdrawing groups on a benzene ring might make
interpreting the oop bending challenging. Refer to the textbook regarding N-H, O-H, and
C=O stretches for guidance.]
6. (a) Rank the following three compounds from highest (1) frequency to lowest (3)
frequency for the C=C stretch.
O
(b) Briefly explain (in no more than 2 sentences) why the frequency of the C=C
stretch is different for cyclopentenone and cyclopentene.
(c) Briefly explain (in no more than 2 sentences) why the frequency of the C=C
stretch is different for cyclopentene and cyclobutene.
CHEM 4341/6371
A
C
1 A-C: C8 H10
B
Part A
CHEM 4341/6371
D
2 D-G: C9 H12
E
F
G
Part A
CHEM 4341/6371
H:
J
3 H-J C9 H12 O
I
Part A
Part A
CHEM 4341/6371
4. Match the following C 7 H 14 O 2 compounds to their corresponding IR spectrum.
1
O
2
O
3
O
O
4
O
O
O
HO
K
L
M
N
Part A
CHEM 4341/6371
5. Match the following C 8 H 9 NO 2 compounds to their corresponding IR spectrum.
5
NH2
6
O
O
OH
7
NH2
O
HO
NH
O
Q
OH
P
R
8
NO2
CHEM 4341/6371
PART B
1. (a) Provide a brief explanation (< 3 sentences) with reference to carefully drawn resonance
structures as to why the C=O stretching peak of 3-methylamino-5,5-dimethyl-2cyclohexenone appears at <1600 cm-1, which is ca. 100 cm-1 lower than the frequency of the
C=O str. peak in 2-cyclohexenone. [You must draw valid resonance structures in support of
your explanation to receive full credit].
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(b) Ketones typically give a C=O str. peak at ca. 1720 cm-1. Provide a brief explanation (< 3
sentences) with reference to carefully drawn structures as to why the C=O stretching peak of
5,5-dimethyl-1,3-cyclohexanedione appears ca. 100 cm-1 lower, at 1613 cm-1 [To received full
credit you must draw structures that support your explanation). Note that the IR spectrum also
has a very broad peak from ~3200 to ~2400 cm-1.
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CHEM 4341/6371
PART B
2. Match IR spectra (A-L) to compounds 1-8 (note: there are four choices of spectra for each set
of three isomers)
(a) All C 7 H 12 O; spectra A-D
1
2
3
(b)All C 8 H 16 ; spectra E-H
4
5
6
8
9
(c) All C 9 H 10 ; spectra I-L
7
For the following questions, provide a single best answer that is consistent with the data
provided. Partial credit is available for structural features that are correctly identified. In some
cases more than one structure might be worth full credit.
3. Identify compound 10, C 10 H 14 [only IR spectrum provided]
4. Identify compound 11, C 14 H 14 [only IR spectrum provided]
5. Identify compound 11, C 8 H 9 NO [IR, 13C and 1H NMR spectra are provided]
Question 2(a): Compounds 1-3: C7H12O
A
B
1727 cm-1
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1674 cm-1
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C
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D
1699 cm-1
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1714 cm-1
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Question 2(b): Compounds 4-6, C8H16
E
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F
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G
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H
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Question 2(c): Compounds 7-9, C9H10
I
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J
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K
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L
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Question 3: Compound 10, C10H14
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Question 4: Compound 11, C14H14
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Question 5: Compound 12, C8H9NO
1668 cm-1
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3H
δ199
4H
2H
CHEM 4341/6371
PART B
CHEM 4341/6371
PART B
CHEM 4341/6371
PART B
CHEM 4341/6371
PART B