B.Sc. Third year Undergraduate degree course Semester Fifth Organic chemistry
Chapter - Spectroscopy
NMR Spectroscopy
Multiple Choice questions
1. NMR spectroscopy is
useful for determining the type and number of _______ atoms in organic molecules.
(a) hydrogen
(b) carbon
(c) halogen
(d) hetero atoms
Answer. (a)
2. What is the
multiplicity of the methylene hydrogens of a carbon that is attached to a
methyl group and to a methyl group and to a methoxy group?
(a) doublet
(b) singlet
(c) quartet
(d) triplet
Answer. (c)
3. Each of the following
compounds has a singlet in its 1H NMR spectrum. Which compound would
have its singlet at the highest frequency?
(a)
1-bromo-2,2-dimethylpropane
(b) ethyl methyl ether
(c) ethyl-tert-butyl
ether
(d) 1,2-dibromoethane
Answer. (b)
4. Which of the
following compounds would have the signal for its methylene hydrogens farthest
downfield?
(a) ethyl chloride
(b) ethyl iodide
(c) ethyl bromide
(d) ethyl fluoride
Answer. (d)
5. How many signals
would you expect to see in the 1H NMR spectrum of chlorocyclobutane?
(a) 1
(b) 3
(c) 4
(d) 5
Answer. (d)
6. What is the multiplicity
of the OH group of an alcohol in a solution that contains a trace amount of
acid?
(a) doublet
(b) quintet
(c) quartet
(d) singlet
Answer. (d)
7. How many signals
would you expect to see in the 1H NMR spectrum of butane?
(a) 1
(b) 2
(c) 3
(d) 4
Answer. (b)
8. Which of the
following will occur farthest downfield?
(a) the hydrogens of
benzene
(b) the hydrogens of
ethyne
(c) the hydrogens of
dimethyl ether
(d) the hydrogens of H COH
Answer. (d)
9. How many signals will
vinyl chloride have in 1H NMR spectrum?
(a) 1
(b) 2
(c) 3
(d) 4
Answer. (c)
10. How many signals
does 2,2,4-trimethylpentane have in its 1H NMR spectrum?
(a) 2
(b) 3
(c) 4
(d) 5
Answer. (c)
11. How many signals
would you expect to see in the 1H NMR spectrum of 2-methylpropene?
(a) 2
(b) 3
(c) 4
(d) 5
Answer. (a)
12. Which of the
following compounds is frequently used as an internal reference in 1H
NMR spectroscopy?
(a) TNS
(b) DMF
(c) TMS
(d) DMSO
Answer. (c)
13. Which of the
following describes the 1H NMR spectrum of 1,2-dichloroethane?
(a) one doublet
(b) two triplets
(c) two doublets
(d) one singlet
Answer. (d)
14. What is the
multiplicity of the CH2, hydrogens in CH3OCH2CH2OCH3?
(a) a singlet
(b) a triplet
(c) a quartet
(d) a doublet
Answer. (a)
15. What would be the
splitting of the protons on the CH2 groups of butane?
(a) doublet
(b) sextet
(c) triplet
(d) singlet
Answer. (c)
16. Only one signal is
present in the PMR spectra of
(a) C₂H4, C3H6
(b) C₂H6, C5H12
(c) C8H18,C2H6
(d) All
Answer. (d)
17. A proton Hb is
coupled to four equivalent protons Ha.The
multiplicity and relative intensity of lines in the signal Hb is
(a) Doublet, 1: 4:9.
(b) Triplet 1: 4: 6
(c) Quintet, 1: 4: 6: 4:
1
(d) Quartet 1: 4: 6:
4:4.
Answer. (c)
18.The compounds showing
only a single peak in its PMR spectrum are: Acetone (I), Ether (II), Methyl
acetate (III), Dibromoethane (IV), Chlorobromoethane (V).
(a) I, II, IV
(b) II, III, V
(c) I, III, V
(d) III, IV, V
Answer. (a)
19. The aldehydic proton
appears much downfield in the PMR because the aldehydic proton is
(a) Strongly shielded
(b) It lies in the
deshielding zone of the carbonyl group
(c) It occurs at 10 8
ppm
(d) All
Answer. (d)
20. The actual value of nuclear spin depends on
(a) Mass number
(b) Atomic number
(c) Both a and b
(d) Shielding effect
Answer. (c)
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