Perform analysis of IR spectra for acetone and Benzaldehyde. Fill out the attached chart for each spectra.
The Correct Answer and Explanation is :
Infrared (IR) spectroscopy is a powerful analytical technique used to identify functional groups within organic molecules by analyzing the vibrational transitions of chemical bonds. Both acetone and benzaldehyde are carbonyl-containing compounds, and their IR spectra exhibit characteristic absorption bands corresponding to their functional groups.
Acetone (Propanone):
Acetone is a simple ketone with the molecular formula C₃H₆O. Its IR spectrum displays several key absorption bands:
- C=O Stretching: A strong absorption band appears around 1715 cm⁻¹, indicative of the carbonyl (C=O) stretching vibration typical for ketones.
- C–H Stretching: Methyl (–CH₃) groups exhibit C–H stretching vibrations between 2990 and 2870 cm⁻¹. These bands are generally of medium intensity.
- C–H Bending: Bending vibrations of the methyl groups manifest as medium to strong absorptions near 1450 cm⁻¹ and 1375 cm⁻¹.
Benzaldehyde:
Benzaldehyde is an aromatic aldehyde with the molecular formula C₇H₆O. Its IR spectrum is characterized by the following prominent absorption bands:
- C=O Stretching: A strong absorption band around 1706 cm⁻¹ corresponds to the aldehyde carbonyl stretching vibration.
- Aromatic C=C Stretching: The aromatic ring exhibits C=C stretching vibrations, resulting in absorption bands near 1600 cm⁻¹ and 1583 cm⁻¹.
- Aldehyde C–H Stretching: Weak bands around 2814 cm⁻¹ and 2757 cm⁻¹ are due to the stretching vibrations of the aldehyde C–H bond.
- Aromatic C–H Stretching: The C–H stretching vibrations of the aromatic ring appear as absorptions between 3100 and 3000 cm⁻¹.
By analyzing these characteristic absorption bands, one can identify and distinguish between acetone and benzaldehyde using IR spectroscopy. The position and intensity of these bands provide insights into the functional groups present within each molecule, facilitating their identification and structural elucidation.