Problem Set 3 Spectroscopy PDF

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Problem Set 3 Spectroscopy- CHM2120 ORGANIC CHEMISTRY...

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CHM 2120 – Problem set 3 In this assignment: - NMR spectroscopy - IR spectroscopy - Problem-solving and structure identification 1. Associate each of the following IR spectra with one of the following compounds and justify your answer. a. Propanoic acid b. 2-Pentanol c. Benzyl alcohol d. Acetophenone

Problem set 3 – NMR, IR 1. cont.

2

Problem set 3 – NMR, IR 2. Associate each of the following IR spectra with one of the following compounds and justify your answer. a. 2-Propyn-1-ol b. 1-Pentyne c. 4-Methylpentanenitrile d. p-Acetylbenzonitrile

3

Problem set 3 – NMR, IR 2. Cont.

4

Problem set 3 – NMR, IR 3. Give the number of peaks expected in the 1H NMR for the indicated protons in each of the following structures: a)

b)

O

H3 C

CH3

C H2

c) H3 C

C H2

O

H

O

CH3

Cl H

d)

e)

f)

H3 C H3 C

CH3 H

H2 C

H2 N O

H

CO2H

H CH3

O

4. How many signals would be expected in the 1H NMR of the following molecules? a)

b)

O

c)

O

H

O

Cl

CH3 H

d)

e)

f)

H3C CH3

H3C

H2 C

O O

H

O

O

5

Problem set 3 – NMR, IR 5. Explain the following differences in chemical shift. δ = 6.7 ppm

Me a) Me

b) H

O H

O

H H

δ = 7.1 δ = 7.7 ppm

δ = 6.1 ppm c)

O O

H2 C

δ = 4.41 ppm C H2

O

d)

CH3

Me N

H

δ = 5.6 ppm

H

δ = 4.2 ppm

δ = 3.6 ppm

6. Determine the structure of the following unknowns using the table to fill in your answers. a.

Signal

δ

Integration

Multiplicity

Comments

A

B

C

6

Problem set 3 – NMR, IR b.

Signal

δ

Integration

Multiplicity

Comments

A

B

C

D

E

7

Problem set 3 – NMR, IR c.

Signal

δ

Integration

Multiplicity

Comments

A

B

C

D

E

8

Problem set 3 – NMR, IR 7. Determine the most likely structure of a compound, with the molecular formula C9H12, which gave a 1H NMR spectrum consisting of: a doublet at δ 1.25 a septet at δ 2.90 and a multiplet at δ 7.25

I

II

III

IV

V ]

8.

A compound with the molecular formula C10H13Cl gave the following 1H NMR spectrum: singlet, δ 1.6 singlet, δ 3.1 multiplet, δ 7.2 (5H) The most likely structure for the compound is: Cl

Cl

I

Cl

II

III Cl

Cl

IV

V

9. Determine the likely structure for a compound A (C6H10O), which is found to decolorize bromine in carbon tetrachloride. Its spectral data is as follows: 1

H NMR triplet, δ 1.0 singlet, δ 2.4 singlet, δ 1.4 singlet, δ 3.4 quartet, δ 1.6

IR 2200 cm-1 (sharp) 3300 cm-1 (sharp) 3500 cm-1 (broad) OH

OH

OH

I

II

III

OH OH

IV

V

9

Problem set 3 – NMR, IR 10. Briefly explain how you might distinguish between the following substances by comparing their 1H-NMR spectra: O O

O

O

I

II

11. An unknown compound has the formula C6H12O. Elucidate the structure of the molecule by scrutinizing its IR and 1H NMR spectra, shown below.

Signal

δ

Integration

Multiplicity

Comments

A B C D E

10

Problem set 3 – NMR, IR 12. An unknown compound, I, has the formula C3H7NO2. Elucidate the structure of I by scrutinizing its IR and 1H NMR spectra, shown below.

Signal

δ

Integration

Multiplicity

Comments

A

B

C

11

Problem set 3 – NMR, IR 1.

2.

3.

12

Problem set 3 – NMR, IR 4.

5.

6.

13

Problem set 3 – NMR, IR 7.

8.

9.

14

Problem set 3 – NMR, IR 10.

11.

12.

15

Problem set 3 – NMR, IR 13.

14.

15.

16

Problem set 3 – NMR, IR 16.

17.

18.

17

Problem set 3 – NMR, IR 19.

20.

21.

18

Problem set 3 – NMR, IR 22.

23.

24.

19

Problem set 3 – NMR, IR 25.

26.

27.

20

Problem set 3 – NMR, IR 28.

29.

30.

21

Problem set 3 – NMR, IR 31.

32.

33.

22

Problem set 3 – NMR, IR 34.

35.

36.

23

Problem set 3 – NMR, IR 37. Chemical Formula: C 5 H8 O Note: long-range coupling is observed in this example

2H

3H triplet 2H multiplet 1H

4

3

2 PPM

1

0

38. Chemical Formula: C5 H8 O 2H triplet

Note: another compound that exhibits long-range coupling 3H

2H multiplet 1H

5

4

3

2

1

0

PPM

39.

24

Problem set 3 – NMR, IR 40. Chemical Formula: C 5 H8 O

2H

2H 1H triplet

Note: This compound exhibits long-range coupling

2H (multiplet)

1H

4

3

2 PPM

1

0

41.

42.

25

Problem set 3 – NMR, IR 43.

44.

45.

26

Problem set 3 – NMR, IR

46. 2H 2H

Chemical Formula: C 7H 5 BrO

1H

9

8

7

6

5

4

3

2

1

0

PPM

47.

48.

27

Problem set 3 – NMR, IR 49.

50.

51.

28...