Organic Spectroscopy (H NMR) MCQs for CSIR NET, GATE - ChemContent

Vijay Ishwar
0

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-C6H13CCH

            (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

Chapterwise MCQs

Topicwise MCQs

Thanks for visiting our site, Hope to see you soon! 😊

Post a Comment

0Comments

Post a Comment (0)