Lehman, Experiment 13 (modified)
IR Spectroscopy

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Read Lehman pp. 102-108
Select a partner. Complete the handout: IR (Infrared) Spectroscopy; turn-in with answers to the following activites.

I.  a) Match the following functions (ether, ketone, carboxylic acid, nitrile, ester, amide, amine, alcohol) with the correct spectra:

A

B

C

D

E

F

G

H

(Data I.a.1 and I.a.2 accompany the second handout: MS: Mass Spectrometry, which is to be completed with your partner after completing part I.a of the IR handout.)

1) Consult the weight percent, molecular weight data from the following:

A

B

C

D

E

F

G

H

2) Consult the mass spectrograms: (Answer the questions of the MS handout, turn-in at the end of today's lab.)

A

B

C

D

E

F

G

H

b) After completing the identification of the eight compounds, show your form to Dr. R. who will then provide each of you with an individual unknown. Run the IR of the unknown and identify its respective function. Attach the spectra to the form that is turned in. 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.

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II.  Draw all of the possible resonance structures for compounds # 1-5.

III.  a) Estimate the relative order of vibrational frequencies for the carbonyl bands in each of the compounds in #II; place the compounds in order of  decreasing frequency.
b) Briefly explain the reasons for the differences in C=O bond character.

IV.  Explain how utlraviolet (UV) spectroscopy could distinguish benzophenone from the other four compounds considering their respective wavelengths at their maximum UV absorbance (lambda max).

V. Your research group has been provided the IR spectra of five unknowns A,B,C and D,E. The unknowns are included in the following list of possibilities. You and your partner are the group's IR experts. Identify the compounds and explain the IR spectral evidence which supports your assignment. See IR patterns for aromatic substitutions.

 
VI. Answer Lehman questions 1,3,4 and 5b pg. 108, also 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?