Infared Spectroscopy Problems

1) Which region of the IR spectum might be used to distinguish between the following compounds:

a. 2-butanone and 2-methoxypropene
b. 3-propenol (ally alcohol) and propanal
c. ethylamine and acetonitrile (CH3C=-N)
d. benzene and cyclohexane
e. 1-butyne, 1,3-butadine, and 2-butyne
f. HC=-CCH2NH2 and CH3CH2C=-N
g. acetone and propanal


2) a. Would you expect two enantioners such as (R)-2-bromobutane and (S)-2-bromobtane to have identical or different IR spectra?
b. Would you expect two diastereomers such as meso-2,3-dibromobutane to have identical or different IR spectra?


3) Shown below is the IR spectrum of ethynylcyclohexane. What absorbtion bands can you identify?


4) The following two spectra are of nonane and 1-hexanol. Assign them.


5) The following two IR spectra are of 2-methyl-1-butanol and tert-butyl ethyl ether. Assign them.


6) The following two IR spectra are of butanal and 2-butanone. Assign them.


7) The following two IR spectra are of benzoic and hexanoic acids. Assign them.


8) The following two IR spectra are of cyclohexane and cyclehexene. Assign them.


9) The following two IR spectra are of octanic acid, 2-octanone, and 2-octanol. Assign them.


10) The following two IR spectra are of 1-phenyl-2-butanone and 1-phenyl-1-butanone. Assign them.


11) The following two IR spectra are of 2-cyclohexen-1-one and 5-hexen-2-one. Assign them.


12) Identify the functional groups present in the following IR spectra; the compounds may be alcohols, alkenes, or alkynes. Point out the IR bands that you used in making each assignment.


13) Identify the functional groups present in the following IR spectra; the compounds may be alcohols, aldehydes, keytones, acids, or esters. Point out the IR bands that you used in making each assignment.


14) Identify the functional groups in each compound from the following seven IR spectra.


15) Each of the four compounds for which an IR spectrum is shown below contains two functional groups. Identify the functional groups present in each molecule. Choose from alcohol, ester, alkyne, ketone, or alkene.


16) Match the following six spectra with the following compounds: 1-octanol, 3-methylcyclohexanone, octanoic acid, methyl pentanoate, 3-butenoic acid, and 10-undecenal (an 11 carbon aldehyde with a double bond at the 10 position).


17) Match each of the following five IR spectra with one of the following compounds (notice that there is no spectrum for two of the compounds): 1,5-hexadiene, 1-methyl-1-cyclopentene, 1-hexen-3-ol, dipropyl ether, trans-4-octene, cyclohexane, and 3-hexanol.


18) Use the following eight IR spectra and molecular formulae, propose a structure for each compound.


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