Q11-P - Organic Chemistry (Mcmurry)

Question

Where might the following compound have IR absorptions?

Step-by-Step Solution

Answer

Absorption bands seen at 2210-2260 \(c{m^{ - 1}}\), 1690 \(c{m^{ - 1}}\) and 1640-1680 \(c{m^{ - 1}}\).

Step 1: Absorption spectrum

Absorption spectrum indicates dark lines presence in spectrum when radiation transmitted through a substance indicating absorption at specific wavelengths of electromagnetic radiation.

Step 2: Chart for absorption by specific functional group

The given chart has values for absorption of particular wavelength radiation by specific functional group.

                                         Functional group absorption band

Step 3: Functional groups present in given compound

Here three functional groups are present namely alkene, nitrile group and ketone group. Red atom indicated here is oxygen and blue atom is nitrogen according to book. 

Step 4: Absorption bands in a spectrum

Here three absorption bands will be seen:

• Nitrile group absorption band is seen at 2210-2260\(c{m^{ - 1}}\).
• Ketone group absorption band is at 1690\(c{m^{ - 1}}\). This lower value is due to the presence of the ketone group next to the double bond.
• Alkene group \( - C = C - \)  band at 1640-1680\(c{m^{ - 1}}\).