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Organic Chemistry Multiple Choice Questions and Answers – Nuclear Magnetic Resonance

(1) In NMR spectroscopy, what is the product of Nuclear ‘g’ factor (gN), the nuclear magneton and the magnetic field strength (B0)?
[A] energy of transition from alpha to beta state
[B] chemical shift
[C] spin-spin coupling constant
[D] magnetogyric ratio
Answer: energy of transition from alpha to beta state
(2) An organic compound having the molecular formulae C10H14 exhibited two singlets in the 1H NMR spectrum and three signals in the 13C NMR. What is the compound?

[A] (a)
[B] (b)
[C] (c)
[D] (d)
Answer: (a)

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(3) The 1H NMR spectrum of a dilute solution of a mixture of acetone and dichloromethane in CDCl3 exhibits two singlets of 1:1 intensity. What will be the molar ratio of acetone to dichloromethane in the solution?
[A] 3:1
[B] 1:3
[C] 1:1
[D] 1:2
Answer: 1:3
(4) What will be the strength of coupling between geminal protons in the following molecules?

[A] Decrease as the size of ring increase
[B] Increase as the size of ring increase
[C] Remains same
[D] No relation between the size of the ring & coupling
Answer: Increase as the size of ring increase
(5) What is the value of gyramagnetic ratio of proton?
[A] 41.10 radian/Tesla
[B] 42.57 MHz/Tesla
[C] 26.75 radian/Tesla
[D] 41.10 MHz/Tesla
Answer: 42.57 MHz/Tesla
(6) What are the number of signals in 1H NMR in the given molecules?

[A] 3, 4, 4, 3 respectively
[B] 2, 6, 4, 2 respectively
[C] 2, 4, 6, 2 respectively
[D] 2, 4, 2, 6 respectively
Answer: 2, 6, 4, 2 respectively
(7) How many peaks are expected in low-resolution NMR spectrum of vinyl chloride and ethyl cyclopropane?
[A] 3,5
[B] 5,3
[C] 6,3
[D] 3,6
Answer: 3,5
(8) What will be the NMR frequency in MHz of bare 1H in a magnetic field of intensity 1.4092 tesla (given gN = 5.585 and μN = 5.05 x 10-27 JT-1)?
[A] 60 MHz
[B] 120 MHz
[C] 100 MHz
[D] 15 MHz
Answer: 60 MHz
(9) At room temperature, what is the number of singlet resonances observed in the 1H NMR spectrum of Me3CC(O)NMe2 (N, N-Dimethylpivalamide)?
[A] 3
[B] 4
[C] 5
[D] 2
Answer: 3
(10) An organic compound (MF; C8H10O) exhibited the following 1H NMR special data: 62.5 (3H, s), 3.8 (314, s), 6.8 (2H, d, J 8 Hz), 7.2 (2H, d, J 8 Hz) ppm. What will be the compound among the choices?
[A] 4-ethylphenol
[B] 2-ethylphenol
[C] 4-methylanisole
[D] 4-methylbenzyl alcohol
Answer: 4-methylanisole

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