Spectroscopy Lab Worksheets:

IR Spectroscopy / UV Spectroscopy / Mass Spectrometry / NMR: 1H & 13C

PART I: IR/UV * PART II: MS * PART III: 1H NMR * PART IV: 13C NMR


PART I: IR/UV

Select one or two partners. (No more than 3 members per group.) Complete Part I of the IR/UV/MS handout, IR (Infrared) / UV Spectrosopy & Mass Spectrometry (MS) Lab Worksheet .pdf , using the spectra in the following data sets.

A
B
C
D
E
F
G
H

Run the IR of the unknown and identify its respective function. Attach the spectra to one form which is to be turned in after completing the entire Worksheet. Save the sample; it will be used in subsequent analyses. It cannot be replaced or replenished so be judicious in the amounts that you use and how you handle the sample.

Answer the remaining Worksheet questions.

3. Using on-line resources (See: Chem 227 Web Resources page) find the vibrational frequencies for the carbonyl bands in the following compounds’ IR spectra.

1 Acetophenone
2 Benzaldehyde
3 Benzamide
4 Benzoic acid
5 Benzoyl chloride
6 Methyl benzoate

List their respective order of decreasing carbonyl frequency identifying the compounds by the numbers above, 1, 2, … etc.
____ > ____ > ____ > ____ > ____ > ____


Briefly explain the trend in the respective frequencies based on the C=O bond character.

4. Briefly explain how IR carbonyl and specific other absorbances can distinguish propiophenone from 1-phenyl-2-propanone and p-ethylbenzaldehyde.

5. Briefly explain how utlraviolet (UV) spectroscopy could distinguish propiophenone from 1-phenyl-2-propanone and p-ethylbenzaldehyde. Consider their respective wavelengths at their maximum UV absorbances, (λ max).


6. Your research group has been contracted to conduct independent forensic analyses for the Contra Costa County Distict Attorney. You are to identify 6 unknown samples related to a crime scene by using infrared analysis. The IR spectra of the six samples are archived on-line for your interpretation: A, B, C, D, E, and F. The unknown compounds are included in the following list of possibilities. You and your partner(s) are the group's IR experts. Identify the compounds and explain the IR spectral data, which support your assignments. (Consult the IR absorbance tables .pdf and the IR patterns for aromatic substitutions.)

 

Benzylalcohol
N-ethyl aniline
p-ethylbenzaldehyde
o-ethyl aniline
2,4-dimethyl benzaldehyde
m-ethyl aniline
3,5-dimethyl benzaldehyde
p-ethyl aniline
2,5-dimethyl benzaldehyde
1-phenyl-2-propanone
Cinnamyl alcohol
propiophenone (ethyl phenyl ketone)
anisole
m-cresol
o-cresol
p-cresol


7. Briefly explain if nujol mulls can be reasonably used to obtain the IR spectra of any solid compound. See the IR spectrum of nujol. If so, are there any functions that nujol could not be used for? If so, what are they?

8. Report your individual unknowns and peak assignments below. (Attach IR spectra to one lab Worksheet for the entire group before turning in the completed Worksheet, being certain to label the spectra with all pertinent information.)

 


PART II: MS

Using your answers to question #2 in Part I, analyze the on-line Mass Spectrograms for each of the functions /molecules below and complete the Table. Provide the most significant structural fragments and their corresponding m/z values which support your assignments from question #2. NOTE: Not all compounds have a molecular ion.

A
B
C
D
E
F
G
H

PART III: 1H NMR

Continue with your partner(s) from Part I. Complete Part III of the NMR handout, 1H NMR Spectrosopy: Interpretation / Prediction & Reactions Lab Worksheet .pdf , using the spectra in the following data sets.

A
B
C
D
E
F
G
H

After completing the identification of the respective structures of the nine compounds, show your completed Worksheet form for this portion of the Worksheet to Dr. R. He will then schedule each of you to be instructed on the use of the 60 MHz FT-NMR and you will then run the 1H NMR of your unknown on the instrument, and then identify its respective structure. Attach all of the group's NMR spectra to one Worksheet form. Answer the Worksheet questions. Turn in one form for your group after completing the entire Worksheet. Save the sample; it will be used in last analysis (13C NMR), which requires a relatively substantial amount of sample. Remember: the sample cannot be replaced or replenished so be judicious in the amounts that you use and how you handle the sample.


PART IV: 13C NMR

Continue with your partner(s). Complete Part IV of the NMR handout, 13C NMR Spectrosopy: Interpretation / Prediction & Reactions Lab Worksheet .pdf , using the spectra in the following data sets.

A
B
C
D
E
F
G
H

Run the 13C NMR of your individual unknown sample that was used in Part III. Using all of the previous spectroscopic and molecular data, draw a proposed structure for the unknown. Attach all of the group's NMR spectra to one Worksheet form. Answer the Worksheet questions. Turn in one form for your group after completing the entire Worksheet.