C13 NMR Spectroscopy MCQ M.Sc. Chemistry third semester CHE-313

M. Sc. Second year Chemistry Postgraduate degree course

Third Semester

CHE - 313 Structural Elucidation by Spectral methods

UNIT - II ¹³C Nuclear Magnetic Resonance Spectroscopy

Syllabus:-Elementary ideas, instrumental methods, chemical shifts (aliphatic, olefinic, alkyne, aromatic, heteroaromatic and carbonyl carbons); Effect of substituents on chemical shifts.

Multiple Choice questions

1. Which is range of ¹³C chemical shift ?
a) 0 -10
b) 0-100
c) 0-150
d) 0-200
Answer. (d)

2.How many percentage of ¹³C is present in nature ?
a) 1.0
b) 1.2
c) 1.1
d) 0.9
Answer. (c)

3. When a proton decoupled spectrum is obtained, the intensity of the carbon resonance are enhance it is called as
a) NOE
b) PPM
c) Hz
d) D.cps
Answer. (a)

4. Percentage of ¹²C is present in nature?
a) 98 %
b) 90%
c) 92%
d) 91 %
Answer. (a)

5. ¹³C has gyromateric ratio is
a) 267.53
b) 266
c) 234
d) 231
Answer. (a)

6. The effect of electronegative atom in ¹³C NMR will be more in

a) 1
b) 2
c) 3

d) All are equal

Answer. (a)

7. How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (b)

8. How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (b)

9. How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (c)

10.How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (b)

11.How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (c)

12. How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (d)

13. How many signals for following compound observed in C¹³ NMR spectroscopy?

a) 1
b) 2
c) 3
d) 4
Answer. (d)

14. Choose the CORRECT statement from the following
a) 13C has more gyromagnetic ration than 1H
b) 13C NMR shows more homonuclear coupling than 1H NMR
c) 13C NMR requires large samples
d) In 13C NMR, chemical shift decreases with increasing electronegativity
Answer. (c)

15. Select the correct statement regarding the effect of chlorine on chemical shift of β carbons in ¹³C NMR for the following structure.

a) Down field
b) Up field
c) No effect
d) signal splitting
Answer. (a)

16. Population of nuclei is given by
a) Van’t hoff equation
b) Boltzmann equation
c) Plank’s eqn
d) Mohr’s eqn
Answer. (b)

17.A compound C8H5O shows 6 peaks in its CMR spectrum. Out of these 4 peaks are form δ128-137, the fifth peak is at high field δ26 while the sixth is at low field δ187.What is structure of compound