Chapter: Organic Spectroscopy
Topic: H NMR Spectroscopy
Content: MCQ Questions & Solutions
Source: CSIR NET, GATE etc. Exams
Quiz PDF
Q1 1H NMR
spectrum of a mixture of benzene and acetonitrile shows two singlets of equal
integration. The molar ratio of benzene: acetonitrile is
[NET Dec
2016]
(a) 1:1
(b) 2:1
(c) 1:2
(d) 6:1
Q2 The compound that exhibits following
spectral data is 1H NMR: δ 8.0 (1H, d,
J= 12.3 Hz), 7.7 (2H, d, J= 8.0 Hz), 6.8 (2H, d, J= 8.0 Hz), 5.8 (1H, d, J=
12.3 Hz), 3.8 (3H, s), 3.0 (6H, s) ppm
[NET Dec
2016]
Q3 The number of signals observed in 1H
NMR spectrum of 3,5-dibromo toluene is:
[GATE 2001]
(a) 3
(b) 4
(c) 2
(d) 6
Q4 The sensitivity of 600 MHz NMR
spectrometer is more than that of a 60 MHz spectrometer because
[GATE 2003]
(a) Population of spin states is
directly proportional to the applied magnetic field.
(b) Population of spin states is
inversely proportional to the applied magnetic field.
(c) According to the Boltzmann
distribution law, the excess population in the lower spin state increases with
increasing applied magnetic field.
(d) The spectral scan width is more for a 600 MHz spectrum compared to a 60 MHz spectrum.
Q5 1H NMR
spectrum of a compound with molecular formula C4H9NO2
shows δ 5.30 (1H, broad), 4.10 (2H, q), 2.80 (3H, d),
1.20 (3H, t) ppm. Structure of the compound that is consistent with the above
data is
[GATE 2003]
(a) CH3NHCOOCH2CH3
(b) CH3CH2NHCOOCH3
(c) CH3OCH2CONHCH3
(d) CH3CH2OCH2CONH2
Q6 The vicinal coupling constant J
expected for the protons Hp and Hq in the compound given
below will be in the range
[GATE 2004]
(a) 0-2 Hz
(b) 4-6 Hz
(c) 8-10 Hz
(d) 12-15 Hz
Q7 An organic compound having molecular
formula C6H11BrO2 exhibits the following peaks
in 1H NMR spectrum. δ 4.1 (2H, q,
J=7.5 Hz), 4.0 (2H, t, J=7.5 Hz), 1.5-2.2 (4H, m), 1.25 (3H, t, J= 7.5 Hz) ppm.
The structure of the compound is
[GATE 2004]
Q8 1H NMR
spectrum [18]-annulene shows
[GATE 2005]
(a) only one
peak at δ 7.2 (18 H)
(b) only one
peak at δ 5.0 (18 H)
(c) two peaks at
δ 9.0 (12H) and δ 3.0 (6H)
(d) two peaks at δ 9.0 (6H) and δ 3.0 (12H)
Q9 Which of the following compounds is
expected to show a sharp singlet for one of its' protons at δ > 8 ppm in 1H NMR
spectrum, given that this signal remains unaffected on shaking the solution
thoroughly with D2O?
[GATE 2006]
(a) CH3CO2H
(b) CH3CONHC6H5
(c) n-C6H13C≡CH
(d) n-C6H13CHO
Q10 Match the structures in List I with
the coupling constant (Hz) given in List II
[GATE 2007]
(a) 1-(i),
2-(ii), 3-(iii)
(b) 1-(ii),
2-(iii), 3-(i)
(c) 1-(iii),
2-(ii), 3-(i)
(d) 1-(iii),
2-(i), 3-(ii)
Q11 The 1H NMR spectrum of HD
consist of a
[GATE 2009]
(a) singlet
(b) 1:1 doublet
(c) 1:1:1
triplet
(d) 1:2:1 triplet
Q12 In the photochemical reaction
[GATE 2009]
formation of the compound [X] can be inferred by the
disappearance of the 1H NMR signal at 1H NMR spectrum of
the starting material: δ 9.7 (1H,
s), 7.8 (1H, d, J=8 Hz), 7.1-6.8 (2H, m), 3.9 (3H, s), 2.5 (3H, s) ppm.
(a) δ 9.7 ppm
(b) δ 7.8 ppm
(c) δ 3.9 ppm
(d) δ 2.5 ppm
Common data for Q13 and Q14
An organic compound [X] (C9H10O) exhibited
the following spectral data
IR: 1680 cm-1
1H NMR: δ 7.8 (2H, d, J= 7.5 Hz), 7.2 (2H, d, J= 7.5 Hz),
2.7 (3H, s) and 2.4 (3H, s)
Compound X on treatment with m-CPBA produced two isomeric
compounds Y(major) and Z(minor).
Q13 Compounds Y and Z respectively are
[GATE 2009]
Q14 The compounds Y and Z can be
differentiated by carrying out basic hydrolysis, because
[GATE 2009]
(a) Y produces
4-methyl phenol and Z is unaffected.
(b) Y produces
4-methyl phenol and Z produces 4-methyl benzoic
acid.
(c) Y is
unaffected and Z produces 4-methyl benzoic acid.
(d) Y is unaffected and Z produces 4-methyl phenol.
Common data for Q15 and Q16
Treatment of W(CO)6 with 1 equivalent of Na(C5H5)
in the solution gives the ionic compound M. Reaction of M with
glacial acetic acid result in product N. The 1H NMR spectrum
of N displays 2 singlets of relative intensity 5:1. When N is
heated, hydrogen gas is evolved and O is produced, O may also be
prepared by refluxing W(CO)6 with cyclopentadiene and H2
is also produced. Treatment of O with an equivalent of Br2
produces P. (Use 18 electron rule as your guide)
Q15 The compounds M and N respectively
are
[GATE 2009]
(a) [(C5H5)W(CO)3]Na and [(C5H5)W(CO)3H]
(b) [(C5H5)W(CO)4]Na and [(C5H5)W(CO)4H]
(c) [(C5H5)W(CO)3]Na and [(C5H5)W(CO)4H]
(d) [(C5H5)W(CO)4]Na and [(C5H5)W(CO)3H]
Q16 The compounds O and P respectively
are
[GATE 2009]
(a) [(C5H5)W(CO)3]2 and [(C5H5)W(CO)3Br]
(b) [(C5H5)W(CO)4] and [(C5H5)W(CO)2Br(THF)]
(c) [(C5H5)W(CO)2(THF)2] and [(C5H5)W(CO)3Br]
(d) [(C5H5)W(CO)3]2 and [(C5H5)W(CO)2Br(THF)]
Statement for linked answer Q17 and Q18
A ketone on treatment with bromine in methanol gives the
corresponding monobromo compound [X] having molecular formula C5H9BrO.
The compound [X] when treated with NaOMe in MeOH produces [Y] as the major
product. The spectral data for compound [X] are:
1H NMR: δ 1.17 (6H, d), 3.02 (1H, m), 4.10 (2H, s)
13C NMR: δ 17, 37, 39,
210
Q17 The compound [X] is
[GATE 2011]
Q18 The major product [Y] is
[GATE 2011]
Common data for Q19 and Q20
N,N-Dimethylformamide (DMF) gives different patterns of signals
for the methyl protons when its' 1H NMR spectrum is recorded at
different temperatures.
Q19 Match the patterns of the NMR
signals given in column I with temperatures given in column II.
[GATE 2013]
(a) i-x, ii-y,
iii-z
(b) i-x, ii-z,
iii-y
(c) i-z, ii-x,
iii-y
(d) i-z, ii-y,
iii-x
Q20 Based on the above data, the
calculated difference in the frequencies of the two methyl singlets, if the
spectrum is recorded on a 300 MHz spectrometer, is ___ Hz.
[GATE 2013]
Ans Key:
1.c 2.c 3.a 4.c 5.a 6.c 7.c 8.c 9.d 10.b
11.c 12.a 13.b 14.b 15.a 16.a 17.d 18.b 19.b 20.[30]
Detailed Solutions
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