Compare the IR spectrum of benzil with meso-hydrobenzoin. Considering carbonyl, OH, aromatic CH, and aliphatic CH absorption bands, describe the similarities and differences you find. meso-hydrobenzoin (final product):
The Correct Answer and Explanation is :
1. Carbonyl Group (C=O) Stretching
- Benzil: The carbonyl stretching absorption for benzil (a diketone) typically appears around 1670-1700 cm⁻¹. This absorption is due to the stretching vibration of the C=O bond in the diketone structure.
- Meso-Hydrobenzoin: This compound has no C=O stretching absorption because it lacks a carbonyl group, having instead hydroxyl (-OH) groups. Thus, there will be no peak in the 1670-1700 cm⁻¹ range for meso-hydrobenzoin.
2. Hydroxyl Group (O-H) Stretching
- Benzil: Since benzil does not contain hydroxyl groups, there will be no absorption related to the O-H stretching around 3200-3550 cm⁻¹.
- Meso-Hydrobenzoin: This compound will show a strong, broad O-H stretching absorption near 3200-3550 cm⁻¹, characteristic of free hydroxyl groups in alcohols. The broadness of the band is due to hydrogen bonding.
3. Aromatic C-H Stretching
- Benzil: Benzil, as an aromatic compound, will have C-H stretching bands in the range of 3000-3100 cm⁻¹.
- Meso-Hydrobenzoin: Meso-hydrobenzoin, also aromatic, will show similar C-H stretching bands in the same range, but the exact pattern could differ slightly depending on how substituents affect the aromatic ring’s symmetry.
4. Aliphatic C-H Stretching
- Benzil: There are no aliphatic C-H stretches in benzil because it doesn’t contain alkyl groups.
- Meso-Hydrobenzoin: This compound may show weaker aliphatic C-H stretches due to the presence of potential -CH2 or -CH3 groups associated with its alcohol functional group.
Key Differences:
- Carbonyl Group: Benzil will show a strong C=O absorption, while meso-hydrobenzoin will not.
- Hydroxyl Group: Meso-hydrobenzoin will show a strong O-H stretch, which benzil lacks.
- Aromatic C-H: Both compounds will exhibit aromatic C-H stretches in the same region, but meso-hydrobenzoin may show subtle differences due to the presence of alcohols.
- Aliphatic C-H: Meso-hydrobenzoin may have a weak aliphatic C-H stretch, while benzil will not.
This comparison covers the major differences and similarities in the IR spectra of these compounds based on their functional groups. Would you like me to generate an IR spectrum based on this?