NMR questions

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1 
 
NMR Questions 
 
1. Which of the following is not a magnetic nucleus? 
 
 19F 
 16O 
 13C 
 31P 
2. The highest energy difference between  and  spin states can be observed under a magnet with: 
 Bo= 0 T 
 Bo= 0.1 T 
 Bo= 2 T 
 Bo= 11 T 
 
3. What splitting pattern in the 1H NMR spectrum would you expect for the hydrogen atom(s) colored 
red in the compounds shown below? 
Your choices are: s singlet d doublet t triplet q quartet m multiplet. 
 
A 
 
 
 
 B 
 
 
 C 
 
 
 
D 
 
 E 
 
 F 
 
 
4. Which of the following compounds would be expected to show spin-spin splitting in their 1H NMR 
spectra? 
 
Compound Splitting 
No 
Splitting 
 Compound Splitting 
No 
Splitting 
 
(CH3)3C-O-CH3 
 
 
 (CH3)2CH-O-CH3 
 
Br-CH2CH2CH2-Br 
 
 
 Br-CH2CH2-Br 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 
 
5. If you needed to distinguish each of the compounds in the following pairs (A & B) from 
each other, which spectroscopic method (IR or 1H NMR would be best (most certain)? 
Assume that you do not have a reference sample of either compound for direct 
comparison. 
Compound A Compound B IR NMR 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6. There were 6 samples of organic compounds that have molecular formula C5H10O2, and all of 
them are isomeric with the descriptions as follows: 
• None of the compounds is branched 
• There is no O-H absorbance in the IR spectra 
• There IR spectra show a strong sharp band between 1720-1750 cm-1. 
Determine the structures of all isomers by using the information given above and analyzing the 1H NMR 
spectra given below. 
 
 
3 
 
 
 
 
 
 
4 
 
 
 
 
 
 
 
 
5 
 
7. Giving the data below, answer the following question: 
Elemental Analysis: C, 35.17; H, 4.64. 
 
 
 
 
6 
 
 
 
a. Mwt= 
b. Number of C’s= 
 
 
7 
 
c. Number of H’s= 
d. Is there any missing element? 
e. If “yes”, 
i. Can you use MS spectrum to know one of the missed elements? 
ii. Can you use IR spectrum to suggest one more missing element? 
f. Which function group most likely appears at 1743 cm-1 in IR spectrum? 
g. What is the molecular formula? 
h. DBE= 
i. Ignoring the solvent signal at  7.2, how many discrete groups of proton signals in 1H 
NMR spectrum? 
j. What structure feature is suggested by the 2 signals at  1.1 and 4.2? 
k. Is there any aromatic protons? 
l. In 13C NMR, which carbon is corresponding to the signal at d 164.5? 
m. In units of Hrtz, how far the signal at  4.8 from TMS, if the spectrum was obtained on a 
100 MHz spectrometer? 
n. If we used CDCl3 as a solvent, sketch the 1H NMR spectrum. 
o. Draw the structure of the unknown compound. 
p. Which fragment is corresponding to m/z 136 and 138? 
q. What structure feature is suggested by the signal at  4.8 (draw the structure and circle 
the proton)? 
 
8. Can you suggest a chemical structure for a compound with the following data: 
Formula: C5H10O 
 
 
 
8 
 
 
9. Can you suggest a chemical structure for a compound with the following data: 
Formula: C8H14O3 
 
 
 
9 
 
 
10. Can you suggest a chemical structure for a compound with the following data: 
MF: C8H14. 
 
 
 
10 
 
 
11. Can you suggest a chemical structure for a compound with the following data 
Elemental Analysis: C, 93.94; H, 6.06 
 
 
 
11 
 
 
 
 
 
12 
 
 
12. Given the spectra analysis from an unknown sample as shown below 
 
 
 
13 
 
 
 
 
 
14 
 
 
13. A sample was analyzed and it was found the elemental analysis as: C = 64.85%, H = 6.35%. 
Given the spectra analysis from this sample as shown below: 
 
 
 
15 
 
 
a. Determine the empirical formula. 
MWt= 
b. C’s= 
H’s= 
b. Calculate the number of double bond equivalents. 
 
d. What functional groups are consistent with both the IR spectrum and molecular formula? 
 
e. How many non-equivalent carbon environments can be determined from the 13C NMR spectrum? 
 
f. What other structural information can be obtained from the 13C NMR spectrum? 
 
g. How many non-equivalent hydrogen environments can be determined from the 1H NMR spectrum? 
 
h. What other structural information can be obtained from the 1H NMR spectrum? 
 
i. Suggest a structure consistent with all the spectral data presented and your answers to the question 
above.