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SIKKIM UNIVERSITY

Department of Chemical SciencesModern Physical Methods in Chemistry II: CH 401

Unit Test-3: June, 2014

Dr. Biswajit G. Roy

Total Marks: 50 Time: 2 h

Section A (Answer all, 10x1=10)

1. Which of the following is the correct order of increasing chemical shift range?

a)1HD

4. Match the19

F NMR shifts a. -219, b. -116, c. -68, d. -63 with the following compounds.

e. , f., g. , h. and choose the correct match.

a. a-e, b-f, c-g, d-h

b. a-f, b-g, c-e, d-h

c. a-h, b-f, c-g, d-ed. a-g, b-h, c-f, d-e

5. 13C chemical shift Cvalue of 14 carbon of H3C C C O

CH31 2 3 4

are respectivelya. 19.5, 62.4, 88.5, 28.0

b. 19.5, 28.0, 88.5, 62.4

c. 28.0, 19.5, 62.4, 88.5

d. 28.0, 62.4. 19.5, 88.5e.

f.

P.T.O

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F

F

FF

NO2A B C D

6. INADEQUATE spectrum need very high concentration of sample and long NMR time

mainly becausea.

13C has low natural abundance.

b.13

C has low gyromagnetic constant.

c. Probability of two consecutive carbon nucleus to be13

C is once in 1000 molecule.d. All of the above.

7. What is NOT true about HMQC (Heteronucleur multiple quantum coherence)?

a. It shows correlation between carbon and hydrogen.b. It is a polarization transfer technique.

c. It is much more sensitive compared to C-H COSY.d. It shows 2 and 3 bond correlation between carbon and hydrogen.

8. What is NOT true about HMBC?

a. It 2D NMR technique.

b. It is useful to deduce the structural framework of a molecule.c. It shows 2 and 3 bond correlation between carbon and hydrogen.

d. It is a proton decoupled technique.

9. Which of the following statement is NOT true?

a. In gated decoupling NOE enhancement is achieved but decoupling effect is lost.

b. In inverse gated NOE enhancement is lost and decoupling effect is preserved.

c. In normal heterogeneous decoupling both decoupling effect and NOE

enhancement are achieved.

d. In gated decoupling all hydrogen nuclei is irradiated during data acquisition.

10. Which of the following protons are chemically equivalent but magnetically non-equivalent?

FF

HH

HH

H

H Cl

Cl

OMe

NO2

Br

Cl

H

Cl

H H

I II III IV

Section B

Answer any Four (4 x 10 = 40)

1. a) Mach following13

C NMR values to designated carbons. 2 + 3 = 5

A)

a) I, II and IVb) I and IVc) II and IVd) II, III and IV

e) None of the above

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O O

O

O

O

a bc

d

i) 72.6; ii) 68.4; iii) 40.6; iv) 95.0

B)

O O

O

a

b

cd e

f

i) 196.9; ii) 167.7; iii) 141.7; iv) 137.5; v) 128.6; vi) 96.4

b) Give reason for marked difference of CMR values of carbons of following compound. 2

c) Deduce the structure of following compound (C7H7ClO)? 3

2. a) Deduce the structure of following compound (C4H10O)? 4

13C NMR (CDCl3, 100 MHz): 10 (q), 23 (q), 32 (t), 69 (d);

b) A compound having molecular formula C6H8O2showed only a singlet in1H NMR at 2.5 ppm and two

peaks in proton decoupled13

C NMR at 38 (below at DEPT 135) and 209 ppm (doesnt appeared in DEPT).

Suggest the structure of the compound. 4

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c) 31

P NMR is more sensitive than19

F NMR- Do you agree or disagree? Give reason supporting your

choice. 2

3. An organic compound has the molecular formula C12H17NO. Identify the compound using the

spectroscopic data given below . 10

max (KBr disc): 3296, l642 cm-1

1H NMR (CDCl3 solution):07.23-7.42 (m, 5H);5.74 (brs, exch. D2O , lH); 5.14 (q, J = 6.7Hz, lH); 2.15 (t, J = 7.1 Hz, 2H); 1.66 (m, 2H);

1.48(d,J = 6.7 Hz, 3H); 0.93 (t,J= 7.3 Hz, 3H) ppm.

13C{

IH} NMR (CDC13solution): 172.0 (C), 143.3 (C), 128.6, 127.3, 126.1,48.5 (CH),

38.8 (CH2), 21.7 (CH3), 19.1 (CH2), 13.7 (CH3)ppm.

Mass spectrum: m/e 191(M+, 40), 120(33), 105(58), 104(100), 77(18), 43(46).

4. A compound having molecular formula C10H16O, gives following 1D and 2D NMR spectra.Draw the structure and assign each atom with NMR value. Give explanation for you logical

structural elucidation and assignments. 7

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b) Deduce the structure of following compound (C8H19N)? 3

5. A compound having molecular formula C9H16O4, gives following 1D and 2D NMR spectra.

Draw the structure and assign each atom with NMR value. Give explanation for you logical

structural elucidation and assignments. 10

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