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Faculty of Natural Sciencesand TechnologyDepartment of Chemistry

THE EXAM FOR THE COURSE KJ3021 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

2 December 2011

Permitted tools: C – tables: 1H and 13C shifts, coupling constants, common NMR solvent data – approved calculator – ruler

Contact person: Assoc.Prof. Nebojša Simić, 735 90 829 mobile: 93 65 95 79 Institutt for kjemi

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Problem 1. 1) What happens with microscopic magnetizations immediately after the 90ºx' pulse?

a) They are all aligned along the +y-axis b) Most of them are aligned along the +y-axis c) They all possess phase coherence d) Some of them start to precess with the same phase e) They generate polarization

(3 pts)

Problem 2. Which methods are commonly used for distinguishing enantiomers by NMR? (5 pts)

Problem 3. Olefinic and aromatic protons do not show the desired effect with lanthanoid shift reagents

(LSR). Yet, it is possible to achieve such an effect. How?

(5 pts) Problem 4 Mark (circle the letter before) the correct answer: a) Double- and zero-quantum transitions, induced by electromagnetic radiation, are allowed by quantum mechanical rules. b) Single quantum transitions are the most important in the NOE spectroscopy c) NOE is based on zero- and double-quantum relaxation processes. d) Quadrupolar relaxaton mechanism is the most important for NOE. (3 pts) Problem 5. On the scheme below a pulse sequence of an 1D NMR experiment is shown.

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a) Which experiment is in the matter? b) What is achieved by this experiment? (6 pts) Problem 6. The HMQC and HSQC experiments give practically the same information about the molecule. What is the main difference between them? (6 pts) Problem 7. What is the reason for decaying of the FID (free induction decay) curve?

(5 pts) Problem 8. What improvement offers ROESY in comparison to NOESY?

a) cross-peaks visible even for very distant nuclei b) possibility to observe heteronuclear NOE c) cross-peaks unaffected by correlation time

(5 pts) Problem 9. 1D and 2D NMR spectra of the compound with the given molecular formula are shown on pages 4-7. a) Elucidate the structure of the compound. (25 pts)

b) Assign all 13C and 1H resonances. (11 pts) Problem 10. One of the exchangeable protons of the compound shown on page 8 was substituted with an alkyl group. By using 1D and 2D NMR spectra shown on pages 8-10, answer: a) Which alkyl group is it and in which position? b) Determine the stereochemistry at positions 2, 3 and 4 (wavy bonds). c) Assign all of the proton and carbon signals. d) Explain the multiplet at ~1.2 ppm. (26 pts)

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Problem 9

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Problem 9

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Problem 9

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Problem 9

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Problem 10

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Problem 10

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Problem 10

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Table 1. H,H-Coupling constants for common groups of organic compounds

Type J (Hz) Type J ( Hz)

12-15 2-9

0

6.5- 7.5

5.5- 7.0 aa 5-8 ae 2-4 ee 2-4

0.5- 3

7-12

13-18

4-10

0.5- 2.5 0

9- 13 2- 3

1- 3

2- 4

o- 6- 9 m- 1- 3 p- 0- 1

1-2 1.6-2.0 1-3 0.6-1.0 1-4 1.3-1.8 2-3 3.2-3.8

1-2 2.0-2.6 1-3 1.5-2.2 1-4 1.8-2.3 2-3 2.8-4.0

1-2 4.6-5.8 1-3 1.0-1.8 1-4 2.1-3.3 2-3 3.0-4.2

1-2 4.9-5.7 1-3 1.6-2.6 1-4 0.7-1.1 1-5 0.2-0.5 2-3 7.2-8.5 2-4 1.4-1.9

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Table 2. 1H shifts

relative to TMS 12 11 10 9 8 7 6 5 4 3 2 1 0 -1

H3C-Alkyl

H3C-C-Hal

H3C-C=C

H3C-CC

H3C-Aryl,-Heteroaryl

H3C-CO

H3C-S-

H3C-SO2-

H3C-N

H3C-O-Alkyl

H3C-O-Aryl, -O-CO-

C-CH2-Alkyl

Cyclopropane

C-CH2-CO

C-CH2-O-

C-CH2-S

C-CH2-NO2

C-CH2-N

C=C-CH2-C=C

N-CH2-CO-

-O-CH2-CO-

-O-CH2-O-, -Aryl

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12 11 10 9 8 7 6 5 4 3 2 1 0 -1

CH-Alkyl

CH-Hal

C-CH-O-

C-CH-N

CO-CH-C=C

CH-Aryl,-NR-,-O-

-CCH Alkine

CH=C-

Ar-H

Alkyl-, Aryl-CHO

Alkyl-OH

Aryl-OH

R-COOH

Alkyl-SH

Aryl-SH

Alkyl-NH2, Alkyl2-NH

Aryl-NH2, Aryl2-NH

R-CO-NH-

-CO-NH-CO

12 11 10 9 8 7 6 5 4 3 2 1 0 -1

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Table 3. 13C shifts

relative to TMS 220 200 180 160 140 120 100 80 60 40 20 0 -20

H3C-C- primary

H3C-S-

H3C-N

H3C-O-

-H2C-C secondary

Cyclopropanes

-H2C-S-

-H2C-N

-H2C-O-

-H2C-Hal F

Cl

Br

I

>CH-C- tertiary

>CH-S-

>CH-N

>CH-Hal F Cl

Br

I

C-C quaternary

C-S-

C-N

C-O-

C-Hal Cl

Br

I

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relative to TMS 220 200 180 160 140 120 100 80 60 40 20 0 -20

Alkines

C=C=C Allenes

C=C Alkenes

Aromatic Compounds

Heteroaromatic Compounds

-S-CN Rhodanides

-N=C=S Isothiocyanates

-O-CN

-N=C=O

-CN

-NC-

>C=N- Azomethines

(-CO)2O Anhydrides

-COOR

-CONHR

-(CO)2NR Imides

-COOH

-COCl

-CHO

>C=O

relative to TMS 220 200 180 160 140 120 100 80 60 40 20 0 -20

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Table 4. Common NMR solvents data sheet