Organic Chemistry I LabSchool of Science & Technology

CHEM 2211L (Fall 2008)GeorgiaGwinnettCollege

Experiment G. Spectroscopy: Mass Spectroscopy (MS), Infrared Spectroscopy (IR), Ultraviolet-Visible Spectroscopy (UV-Vis), Nuclear Magnetic Resonance Spectroscopy (NMR)

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1. Experimental Objectives: The purpose of this experiment is to

a. learn to use the FTIR and UV-Vis instrumentation in the lab.

b. access and analyze spectra on web databases.

c. integrate analysis of MS, IR, UV-Vis, and NMR to determine structure of unknown compounds.

d. present, analyze, discuss results in written report.

2. SPECIAL INSTRUCTIONS:

a. There is no pre-lab quiz . You will not do a lab report in your lab notebook, but instead turn in the lab procedure pages with your solutions to the unknown compounds, plus your print outs from web databases.

b. While each student turns in their own report, you are encouraged to work together to solve the unknown structures.

c. Report is due at the end of the second lab period.

d. Chemicals:

(1) benzoic acid, [65-85-0]

(2) methylbenzoate, [93-58-3]

3. PROCEDURES:

(4) 1. Visit the National Institute of Standards and Technology (NIST) ( webpage. Browse to familiarize yourself with how it is organized. Go to the NIST Chemistry WebBook ( which contains chemical information on thousands of compounds. Search by CAS (Chemical Abstract Services) Registry Number: 78-77-3 and find IR (gas), MS, and UV/Vis spectra. Note that NIST provides the structure for the molecule. Print out a large MS and IR spectrum in the landscape format. Conduct an analysis of the IR and MS of the known compound using the format below. This should be straight-forward for the known compound and will serve as a check of the process before you move on to unknowns.

  1. Molecular weight.
  1. All possible molecular formulas and degree of unsaturation of each possibility.
  1. Possible functional groups present from IR analysis, consistent with molecular. formula and degree of unsaturation.
  1. Possible fragments lost from the molecular ion.
  1. Put together the “puzzle pieces”: rule out or confirm possible molecular formulas, degrees of unsaturation, and propose consistent pieces of the molecule. How can they fit together?
  1. Proposed structure. Argue convincingly that all of the data supports and confirms your proposal.

(4) 2. Conduct a web search of the Spectral Database for Organic Compounds SDBS, ( agree to the disclaimer, and you will arrive at the SDBS Compounds and Spectral Search page. Search by name for 1-bromo-2-methylpropane and find IR, MS, 1H NMR, and 13C NMR spectra. Print the chemical information and all four spectra (use the IR in CCl4) and the accompanying peak data, as appropriate. Conduct an analysis of the known compound using the format below. This analysis should be straightforward for the known compound and will serve as a check of the process before you move on to unknowns.

a. Molecular weight.

b. All possible molecular formulas and degree of unsaturation of each possibility.

c. Possible functional groups present from IR analysis, consistent with molecular formula and degree of unsaturation.

d. Possible fragments lost from the molecular ion.

e. Put together the MS and IR “puzzle pieces”: rule out or confirm possible molecular formulas, degrees of unsaturation, and propose pieces of the molecule consistent with the data. How can they fit together?

f. Analyze the 1H NMR spectrum relative to MS and IR spectra.

1) # of peaks ↔ # of non-equivalent protons.

2) splitting pattern ↔ # of equivalent adjacent protons (n+1 rule).

3) chemical shift ↔ functional group.

4) integrated peak area ↔ relative # ratio of types of protons.

g. Analyze the 13C NMR spectrum relative to MS and IR spectra.

1) # of peaks ↔ # of non-equivalent carbon atoms.

2) chemical shift ↔ functional group.

3) splitting pattern ↔ # of protons on that carbon atom (n+1 rule).

h. Propose a structure. Argue convincingly that all of the data supports and confirms your proposal.

(36) 3. Determine the structures of 6 of the 7 unknowns, A-G, in the Appendix. Use the same analysis protocol you use in 4.a.-h. above, to include f.1)-4) and g.1)-3). Show all your work directly on the page provided. Be concise but thorough.

(3) 4. IR analysis (solid). Under the guidance of your professor, you will run, print, and analyze the IR spectrum of benzoic acid.

(3) 5. IR analysis (liquid). Under the guidance of your professor, you will run, print, and analyze the IR spectrum of methylbenzoate.

Appendix: Unknowns A-G

Solve the structure of 6 of the following 7 unknown compounds, A-G. Each unknown presents, in order, elemental analysis followed by mass, IR, 1H NMR, and 13C NMR spectra. Show all your work in the space provided. Include a structure and name of the unknown in your solution.

Compound A. Elemental Analysis: C, 62.04; H, 10.41; O, 27.55

13C NMR Spectral Data:

singlet, 206.0 ppm
quartet, 27.0 ppm

Compound B. Elemental Analysis: C, 15.40; H, 3.23; contains halogen.

13C NMR Spectral Data:

quartet, 17.7 ppm
triplet, 0.4 ppm

Compound C. Elemental Analysis: C, 90.51; H, 9.49.

13C NMR Spectral Data:

singlet, 140.2 ppmdoublet, 125.7 ppm
doublet, 128.4 ppmtriplet, 31.1 ppm
doublet, 127.9 ppmquartet, 16.1 ppm

Compound D. Elemental Analysis: C, 64.02; H, 4.48; contains halogen.

13C NMR Spectral Data:

singlet, 133.8 ppm
doublet, 129.9 ppm
doublet, 128.9 ppm
doublet, 126.6 ppm

Compound E. Elemental Analysis: C, 59.96; H, 13.42; O, 26.62. The molecular ion (m/e = 60) does not appear in the mass spectrum of this compound.

13C NMR Spectral Data:

doublet, 64.9 ppm
quartet, 26.3 ppm

Compound F. Elemental Analysis: C, 78.65; H, 8.25; O, 13.10.

13C NMR Spectral Data:

singlet, 140.2 ppmdoublet, 125.7 ppm
doublet, 128.4 ppmtriplet, 68.5 ppm
doublet, 127.9 ppmtriplet, 44.6 ppm

Compound G. Elemental Analysis: C, 30.29; H, 2.54; contains halogen. Note that long-range coupling with J 2 Hz is visible in the 1H NMR.

13C NMR Spectral Data:

doublet, 68.1 ppm
singlet, 80.3 ppm
triplet, 22.6 ppm

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