Ir Spectroscopy

Callam

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CHEM – 254 – WI -2009

Problem Set #1 – IR Spectroscopy - KEY
1. Which of the indicated bonds absorbs at the higher frequency in an IR spectrum? a.
O or OH

C=O > C-O b.
N or NH

C=N > C-N c.
H or H

C-H sp2 > C-H sp3

Callam

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CHEM – 254 – WI -2009

2. What major IR absorptions are present above 1500 cm-1 for each compound?

a.

b.

O sp3 C-H stretch 2950 C=O - ketone 1715 cm-1 cm-1

c. O

sp3 C-H stretch 2950 cm-1

sp3 C-H stretch 2950 cm-1 sp2 C-H stretch 3100 cm-1 C=O - ketone 1715 cm-1 C=C alkene 1680 cm-1 O

O d. e. f.

OH

sp3 C-H stretch 2950 sp C-H stretch 3310 cm-1 CC alkyne stretch 2220 cm-1

cm-1

sp2 C-H stretch 3100 cm-1 sp3 C-H stretch 2950 cm-1 C=C alkene 1680 cm-1
OH

h.

OH

i.

Br

sp3 C-H stretch 2950 cm-1 OH -Stretch 3400-3200 cm-1

sp2 C-H stretch 3100 cm-1 OH -Stretch 3400-3200 cm-1 sp3 C-H stretch 2950 cm-1 C=C alkene 1680 cm-1

sp3 C-H stretch 2950 cm-1

Callam

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CHEM – 254 – WI -2009

3. How would you distinguish between the following pairs of compounds using IR spectra?