CH2710 - Exam #4 (Take Home)Date Due: 11/25,26/2013

Section I - Multiple Choice - Choose the BEST answer from the choices given and place the letter of you choice in the space provided.

_____ 1. Energy absorbed by a molecule in the infrared spectrum corresponds to:

A) the amount of energy needed to promote one electron from a bonding to an antibonding orbital B) the amount of energy needed to “flip” the spin of a hydrogen nucleus C) the energy needed to strip a molecule of one electron to generate a cation radical D) the amount of energy needed to increase bond “stretching” and “bending”

_____ 2. Choose the structure which best fits the IR spectrum shown below.

A) B) C) D)

_____ 3. Which of the following statements best describes the base peak in a mass spectrum ?

A) The peak from the least stable radical B) The peak from the species that has the isotope with the highest atomic number C) The peak of highest intensity D) The peak from the molecule minus an electron

_____ 4. The mass spectrum at right is the spectrum of a compound which contains C,H,O, and one other atom. What is the other atom?

A) N B) P C) Br D) Cl

O

H

O OO

A.~ D. HOAY0 0

B. 00 E. (Y°H

C.~ F. ()1[H030.

'00

29.< }-OH

Answer: This compound should show a characteristic broad absorption at 3500 cm-] due to the -ORgroup and a strong absorption at about 1200 cm-] for the C-O, as well as the usual 1500 and1600 cm-l aromatic bands.

MATCH a structure from the list below to the following IR spectra. Place the letter of the structure in theblank provided.

.~

~E5D

!

04000 :tOOO 20DO 1500 1000

HAVENUMB ERI -.1

Spectrum obtained from: SDBSWeb: http://www.aist.go.jpIRIODB/SDBS/

Answer: F

J08 Chapter 12: Structure Determination: Mass Spectrometry and Infrared Spectroscopy

5DO

The following questions refer to the mass spectrum shown below.

100 -HS-NW-l SS9

80-

>,+-''(i')a5 60-+-'CQ)>~0 40-Q)

Ct:::

M+= 156M+= 158

20-

0 ,I II, ~25 50 75 100 125 150

m/zSpectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

175

9. This compound contains C, H, and one other atom. IdentifY the other atom from the mass spectrum andexplain your reasoning.

Answer: There are two molecular ions identified in this spectrum of approximately equal intensity. Thisis characteristic for the presence of a bromine atom C9Br= 50.7% and 81Br= 49.3%).

10. Calculate a possible molecular formula for this compound.

Answer: The M+= 156 is due to the 79Br,so the carbon and hydrogen portion of the molecule is 156 - 79= 77. This mass corresponds to C6Hs. A possible formula for this compound is C6HsBr.

11. Propose a structure for this compound.

Answer: C6HsBr contains four degrees of unsaturation, which is consistent with a benzene ring. Acompatible structure is bromobenzene.

aTh

Test Items for McMurry's Organic Chemistry, Seventh Edition 103

Following is the electron-impact mass spectrum of 2-methylbutane,

_____ 5. How would you describe the peak at m/z 72 ?

A) the base peak B) the molecular ion peak C) the peak containing the heaviest isotopes D) the peak corresponding to the most stable fragment ion

_____ 6. How would you describe the peak at m/z 57 ?

A) the peak corresponding to a butyl radical cation B) the molecular ion peak C) the peak corresponding to a propyl radical cation D) the peak corresponding to an isopentyl radical cation

_____ 7. Nuclear magnetic resonance spectroscopy primarily provides information about a molecule’s:

A) conjugated pi electron system. B) size and formula. C) carbon-hydrogen framework D) functional groups.

_____ 8. When looking at an NMR chart, the right-hand part if the chart is the:

A) high-field, upfield side. B) low-field, downfield side. C) aromatic proton region. D) highly-deshielded proton region.

_____ 9. The exact place on the NMR chart where a nucleus absorbs is the:

A) TMS peak. B) atom’s spin quantum number. C) atom’s chemical shift. D) atom’s atomic number.

20 30 40 50 60 70

m/z80 90 100 110 120

Refer to the mass spectrum of 2-methylbutane shown below to answer the following questions.

100MS- I W- 3448 +-43 57

80

>-+-''w~ 60+-'CQ):>-+=-0 40Q)Ct::

29

7220

010

Spectrum obtained tTom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

12. What peak represents M+?

Answer: The peak at m/z = 72 represents M+.

13. What peak represents the base peak?

Answer: The peak at m/z =43 is the base peak.

14. Propose structures for tTagment ions at m/z = 57, 43, and 29.

Answer:

m/z structure+

CH3CHCH2CH3+

CH3CHCH3

+CH2CH3

574329

104 Chapter 12: Structure Determination: Mass Spectrometry and lrifrared Spectroscopy

_____10. Describe the relationship between the indicated two protons:

A) unrelated B) homotopic C) enantiotopic D) diastereotopic

_____11. Describe the relationship between the indicated two protons:

A) unrelated B) homotopic C) enantiotopic D) diastereotopic

_____12. Describe the relationship between the indicated two protons:

A) unrelated B) homotopic C) enantiotopic D) diastereotopic

_____13. How many types of magnetically non-equivalent protons are in the following molecule?

A) 2 B) 3 C) 4 D) 5

_____14. How many types of magnetically non-equivalent protons are in the following molecule?

A) 2 B) 3 C) 4 D) 5

_____15. Which molecule with the formula C4H8Cl2 would give the following proton NMR spectrum ?

A) B)

C) D)

IdentitY the indicated sets of protons as unrelated, homotopic, enantiotopic, or diastereotopic.

16. ifoH H::

I I

~ ~

Answer: homotopic

17.~H H~

V ClCl~

Answer: enantiotopic

18.~H CH3

" )~<~H H

Answer: diastereotopic

~H HHo .CH3

1~ 'H CH3

Answer: unrelated

For each compound below tell how many types of none qui valent protons there are.

20'cb

four3

Z1HH 4 24

Answer:

1H

Test Items for McMurry's Organic Chemistry, Seventh Edition 113

IdentitY the indicated sets of protons as unrelated, homotopic, enantiotopic, or diastereotopic.

16. ifoH H::

I I

~ ~

Answer: homotopic

17.~H H~

V ClCl~

Answer: enantiotopic

18.~H CH3

" )~<~H H

Answer: diastereotopic

~H HHo .CH3

1~ 'H CH3

Answer: unrelated

For each compound below tell how many types of none qui valent protons there are.

20'cb

four3

Z1HH 4 24

Answer:

1H

Test Items for McMurry's Organic Chemistry, Seventh Edition 113

IdentitY the indicated sets of protons as unrelated, homotopic, enantiotopic, or diastereotopic.

16. ifoH H::

I I

~ ~

Answer: homotopic

17.~H H~

V ClCl~

Answer: enantiotopic

18.~H CH3

" )~<~H H

Answer: diastereotopic

~H HHo .CH3

1~ 'H CH3

Answer: unrelated

For each compound below tell how many types of none qui valent protons there are.

20'cb

four3

Z1HH 4 24

Answer:

1H

Test Items for McMurry's Organic Chemistry, Seventh Edition 113

CH321. I

H3C- C- CH3ICH3

1CH3

Answer: 1 I 1one H3C- C- CH3ICH31

22. ()OI I

~~plane of symmetry2H

3H

Answer: four4H

H3

23.

Cld3 IH CH3

Answer: four CH31

Answer: four

CI

.CH3

24. aCH)

H4

2H

2H 1 planeof symmetry

CHJ,/". ,1 ,I,'

Ij

114 Chapter 13: Structure Determination: Nuclear Magnetic Resonance Spectroscopy

Br

25. a&Br

H1

Answer: two

H2

Br

H1

H2

H3C CH2CH3\ /

26. C= C/ \H H

Answer: five

145H3C CH2CH3

\ /C=C/ \H H2 3

CH327.

<~H

Answer: four

3 1

H~f~~'4 T \,

Predict the splitting patterns you would expect for each proton in the molecules below:

CH3I

28. CH3CHCHCH3ICH3

Answer:

1CH3

1 I 2 2 1CH3CHCHCH3

ICH31

ProtonNo. of adiacent

Protons Splitting

doublet

2 6 septet

Test Items for McMurry's Organic Chemistry, Seventh Edition l/5

T T '- I I I I I I I

64. Which structure of molecular formula C4HgClzfits both the IH NMR and BC NMR spectra shown below?

ylCl

~ClB.ICl

Cl, ...............C. ~ ~ 'ClA.

11 10 9 8 7 6

H8P-00-228

5ppm

4 3 2

200 180 160 140 120

C08-03-793

100ppm

80 60 40 20

Spectra obtained ITom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

Answer: B

Test Itemsfor McMurry's Organic Chemistry, Seventh Edition

D.

~Cl

0

0

125

T T '- I I I I I I I

64. Which structure of molecular formula C4HgClzfits both the IH NMR and BC NMR spectra shown below?

ylCl

~ClB.ICl

Cl, ...............C. ~ ~ 'ClA.

11 10 9 8 7 6

H8P-00-228

5ppm

4 3 2

200 180 160 140 120

C08-03-793

100ppm

80 60 40 20

Spectra obtained ITom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

Answer: B

Test Itemsfor McMurry's Organic Chemistry, Seventh Edition

D.

~Cl

0

0

125

T T '- I I I I I I I

64. Which structure of molecular formula C4HgClzfits both the IH NMR and BC NMR spectra shown below?

ylCl

~ClB.ICl

Cl, ...............C. ~ ~ 'ClA.

11 10 9 8 7 6

H8P-00-228

5ppm

4 3 2

200 180 160 140 120

C08-03-793

100ppm

80 60 40 20

Spectra obtained ITom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

Answer: B

Test Itemsfor McMurry's Organic Chemistry, Seventh Edition

D.

~Cl

0

0

125

T T '- I I I I I I I

64. Which structure of molecular formula C4HgClzfits both the IH NMR and BC NMR spectra shown below?

ylCl

~ClB.ICl

Cl, ...............C. ~ ~ 'ClA.

11 10 9 8 7 6

H8P-00-228

5ppm

4 3 2

200 180 160 140 120

C08-03-793

100ppm

80 60 40 20

Spectra obtained ITom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

Answer: B

Test Itemsfor McMurry's Organic Chemistry, Seventh Edition

D.

~Cl

0

0

125

T T '- I I I I I I I

64. Which structure of molecular formula C4HgClzfits both the IH NMR and BC NMR spectra shown below?

ylCl

~ClB.ICl

Cl, ...............C. ~ ~ 'ClA.

11 10 9 8 7 6

H8P-00-228

5ppm

4 3 2

200 180 160 140 120

C08-03-793

100ppm

80 60 40 20

Spectra obtained ITom: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

Answer: B

Test Itemsfor McMurry's Organic Chemistry, Seventh Edition

D.

~Cl

0

0

125

Spectral Analysis - Problem A

Spectral Analysis - Problem B

Spectral Analysis - Problem C

Spectral Analysis - Problem D

Mass Spectral Data: Base peak at m/z = 43 No definitive molecular ion. Highest discernible peaks m/z = 84 (20% of base peak), m/z=85 (1.2% of base peak)

Spectral Analysis - Problem E - C8H14O3

Spectral Analysis - Problem F

Mass Spectral Data: Molecular ion at m/z =107

Section II - Spectra Analysis - Instructions - Identify the compound described with the data supplied for the following six compounds. “Partial” credit will be given for a structural formula only. The bulk of the points, however, will be allocated to your use of the spectral and other data supplied. THEREFORE, YOU SHOULD CLEARLY STATE HOW YOU USED THE DATA SUPPLIED AND MAKE AN EFFORT TO ASSIGN ANY “DIAGNOSTIC” IR PEAKS, MASS SPEC PEAKS, OR NMR SIGNALS WHICH YOU USED TO ARRIVE AT YOUR FINAL STRUCTURE. You may answer on a separate sheet of paper. Please take the time to make your answers neat, organized, and concise. This does not have to be a term paper. (85 points)