Chem 242
Problem set 1
Name:
Due date: Friday, Jan 29th 2010.
This is an individual problem set. Do not seek help to solve the problems from anybody
and don’t match your spectra with any recorded spectra. Please provide a SCANTRON
for the multiple choice part.
1- Provide the structure corresponding to the each of the following 1H and 13C NMR.
Take a note of the integration ratio or the splitting pattern provided. Draw your answer on
the right of the spectrum. Assign protons on the structure and spectra by alphabets.
a-
b-
c-
d-
e-
f-
g-
2- Provide the structure for the following 13C NMR spectra below.
a-
bC8H8O
cC5H7NO2
dC4H10O2
3. An unknown compound, L, has the formula C5H10O2. Elucidate the structure of L by
scrutinizing its IR, 1H NMR and 13C NMR spectra, shown below.
MULTIPLE CHOICE QUESTIONS
1. Which proton(s) of the compound below would appear as a triplet in the 1H NMR
spectrum?
I
CH3
CH3CH2CH2-O-CH
CH3
V IV III
II
A)
B)
C)
D)
E)
I
The protons on carbon II
The protons on carbon I and V
The protons on carbon III and V
The protons on carbon III and IV
The protons on carbon V
2. What feature would you expect to see in the 1H NMR spectrum of B after subjecting A
to the following reaction?
Cl2
C8H9Cl
+
HCl
heat or light
(chief product)
A
B
A)
B)
C)
D)
E)
There would be only 4 aromatic protons at low field.
The signal for the protons on the benzylic carbon would be a doublet.
The signal for the methyl protons would be a triplet.
The signal for the methyl protons would be a doublet.
The signal for the methyl protons would integrate for only 2 hydrogens.
3. The 1H NMR signal for which of the indicated protons occurs furthest downfield?
III
Cl
H
H
C C C
C CH3
I
H
IV
II
V
A)
B)
C)
D)
E)
I
II
III
IV
V
4. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2,
would consist of two singlets only?
O
O
O
O
O
O
I
II
O
III
O
O
O
IV
A)
B)
C)
D)
E)
V
I
II
III
IV
V
5. The 1H NMR spectrum of which of the compounds below, all of formula C7H12O2,
would consist of a singlet, a doublet and a triplet only?
O
O
O
O
O
I
II
O
III
O
O
O
IV
A)
B)
C)
D)
E)
V
I
II
III
IV
V
6. In NMR terminology, protons Ha and Hb are said to be:
H
Cl
Hb
A)
B)
C)
D)
E)
Ha
Identical
Enantiotopic
Diastereotopic
Homotopic
Mesotopic
O
7. Determine the most likely structure of a compound, with the molecular formula C9H12,
which gave a 1H NMR spectrum consisting of:
a doublet at δ 1.25
a septet at δ 2.90 and
a multiplet at δ 7.25
I
II
III
IV
V
]
A)
B)
C)
D)
E)
I
II
III
IV
V
8. A compound C4H9Br gave the following 1H NMR spectrum:
multiplet, δ 4.1 (1H); multiplet, δ 1.8; doublet, δ 1.7;
triplet, δ 1.0 (3H)
Which is a reasonable structure for the compound?
A) CH3CH2CHBrCH3
B) CH3CH2CH2CH2Br
C) (CH3)2CHCH2Br
D) (CH3)3CBr
9. How many signals will be recorded in the broadband proton-decoupled 13C spectrum of
4-chloro-1-ethylbenzene?
Cl
A)
B)
C)
D)
E)
2
3
4
6
7
10. How will the methyl carbon appear in the proton off-resonance decoupled 13C spectrum
of toluene?
A)
B)
C)
D)
E)
Singlet
Doublet
Triplet
Quartet
Quintet
11. The C7 compound which gives 3 signals in the broadband proton-decoupled 13C
spectrum could be:
A) Heptane
B) 2-Methylhexane
C) 3,3-Dimethylpentane
D) 2,4-Dimethylpentane
E) 2,2,3-Trimethylbutane
12. A downfield (δ 9-10) singlet is observed in the 1H NMR spectrum of:
O
A)
B)
CH3CCH2CH3
H
O
C)
C6H5CH2C
H
O
D)
(CH3)2CHC
H
E)
(CH3)3CC
O
O
C6H5CH2CCH3
13. Consider the expected 1H NMR spectrum of 1,1,3,3-trimethylcyclopentane. Which of
the following is likely to be observed?
A)
B)
C)
D)
E)
7 signals: all singlets
7 signals: 4 singlets, 3 doublets
3 signals: all singlets
3 signals: one singlet, 2 doublets
3 signals: two singlets, one doublet
14. In 13C NMR spectroscopy, the signal due to this type of carbon occurs furthest
downfield.
A) –C≡N
B)
C
O
C)
C
O
C
X
D)
E) –C≡C–
15. What is the molecular formula of this compound?
A)
B)
C)
D)
E)
m/z
84 M+•
85
86
C5H10O
C5H8O
C5H24
C6H12
C4H6O2
intensity
10.00
0.56
0.04
16. What is the molecular formula of this compound?
A)
B)
C)
D)
E)
m/z
78 M+•
79
80
81
C6H6
C3H5Cl
C6H8
C6H9
C3H7Cl
intensity
10.00
1
3.3
0.3
17. The mass spectra of alkyl bromides and chlorides are characterized by an unusually
intense __________.
A) base peak
B) parent peak
C) M+• +1 peak
D) M+• +2 peak
E) None of these
18.
A)
B)
C)
D)
E)
Predict the base peak for 2-chloro-2-methylpropane
m/z 15
m/z 92
m/z 43
m/z 57
m/z 77
19.
A)
B)
C)
D)
E)
A prominent (M+• -18) peak suggests that the compound might be a(n):
alkane
alcohol
ether
ketone
primary amine
20. An organic compound absorbs strongly in the IR at 1687 cm-1. Its 1H NMR spectrum
consists of two signals, a singlet at 2.1 ppm and a multiplet centered at 7.1 ppm. Its
mass spectrum shows significant peaks at m/z 120, m/z 105 and m/z 77. This
information is consistent with which of the following structures?
O
O
I
II
IV
A)
B)
C)
D)
E)
I
II
III
IV
V
O
III
V