Sort the pairs of related compounds by their carbonyl stretching frequencies in cm–1. (There will be three compounds per bin.)
Bin # 1: Slightly higher
Bin #2: Slightly lower
Compounds:
-butanol
-but-2-enal
-heptan-3-one
-hept-4-en-3-one
-cinnamaldehyde
-3 phenylpropanal
To sort the pairs of related compounds by their carbonyl stretching frequencies in cm–1, we need to determine the functional groups present in each compound and how they affect the carbonyl stretching frequency.
The carbonyl stretching frequency in a compound largely depends on the electronic environment around the carbonyl group. Factors such as the adjacent atoms and any double bonds or conjugated systems can impact the stretching frequency. Generally, a higher electron density or resonance stabilization leads to a lower carbonyl stretching frequency, while a lower electron density or lack of resonance leads to a higher carbonyl stretching frequency.
Let's analyze each compound to determine its functional group and how it affects the carbonyl stretching frequency:
1. Butanol: Butanol does not contain a carbonyl group and is therefore irrelevant to this analysis.
2. But-2-enal: This compound contains a carbonyl group (C=O) and a double bond (C=C) adjacent to it. The presence of the double bond creates resonance stabilization of the carbonyl group, resulting in a lower carbonyl stretching frequency.
3. Heptan-3-one: This compound also contains a carbonyl group (C=O) but lacks any adjacent double bonds or resonance structures. Without resonance stabilization, the carbonyl stretching frequency of heptan-3-one will be slightly higher compared to compounds with resonance stabilization.
4. Hept-4-en-3-one: Similar to but-2-enal, hept-4-en-3-one contains a carbonyl group (C=O) and an adjacent double bond (C=C). The presence of resonance stabilization leads to a lower carbonyl stretching frequency compared to compounds without resonance structures.
5. Cinnamaldehyde: This compound contains a carbonyl group (C=O) and a conjugated system consisting of a benzene ring and a double bond. The conjugation and resonance stabilization result in a lower carbonyl stretching frequency.
6. 3 phenylpropanal: This compound also contains a carbonyl group (C=O) and a conjugated system with a benzene ring. Like cinnamaldehyde, the presence of a conjugated system leads to a lower carbonyl stretching frequency.
Based on this analysis, we can sort the compounds as follows:
Bin #1 (Slightly higher):
- Heptan-3-one
Bin #2 (Slightly lower):
- But-2-enal
- Hept-4-en-3-one
- Cinnamaldehyde
- 3 phenylpropanal
Note: While butanol does not have a carbonyl group and is not relevant to this analysis, it can be placed separately or omitted from the sorting process altogether.