How good is HCN addition to aromatic conjugated aldehyde?

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In summary, the reaction of HCN with an aldehyde has a higher yield than with a ketone due to steric strain. However, when comparing the reaction yield with an aromatically conjugated aldehyde (such as Ph-CHO), the yield is expected to be lower than with a regular aldehyde and higher than with a ketone. This is because the phenyl group in the conjugated aldehyde has an electron-donating effect, making the carbonyl carbon less electrophilic. This is due to the stronger repulsion generated by resonance compared to the inductive effect in ketones.
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K.z_z
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Reaction of HCN with an aldehyde has higher yield than HCN with a ketone due to steric strain around the ketone. Then how about reaction yield of HCN with an aromatically conjugated aldehyde (like Ph-CHO) comparing with the previous two reactions?
What I think:
The yield be lower than just with regular aldehyde and higher than with ketone. Since the phenyl group is Electron donating, thus making the carbonyl carbon less Electrophilic. Tell me if I am right or wrong, thank you.
 
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According to me the yeild should be lower than ketones as in ketones only inductive effect operates but in benzaldehyde resonance occurs.resonance as an electron shift effect is stronger and generates more repulsion
 

Related to How good is HCN addition to aromatic conjugated aldehyde?

1. How does HCN addition affect the aromaticity of a conjugated aldehyde?

HCN addition to an aromatic conjugated aldehyde typically results in a decrease in aromaticity due to the formation of a less stable aromatic ring. This is because the addition of HCN breaks the delocalized pi-bonding system in the ring, disrupting the resonance that contributes to its aromaticity.

2. What is the mechanism of HCN addition to aromatic conjugated aldehydes?

The mechanism of HCN addition to aromatic conjugated aldehydes involves the formation of a carbon-carbon double bond between the aldehyde and HCN, followed by an intramolecular rearrangement to form a cyanohydrin. This mechanism is known as the nucleophilic addition-elimination mechanism.

3. Are there any factors that affect the selectivity of HCN addition to aromatic conjugated aldehydes?

Yes, there are several factors that can affect the selectivity of HCN addition to aromatic conjugated aldehydes. These include the electronic nature of the aldehyde, steric hindrance around the reaction site, and the presence of any coordinating groups that may hinder or facilitate the addition of HCN.

4. Can HCN addition to aromatic conjugated aldehydes be used in synthesis?

Yes, HCN addition to aromatic conjugated aldehydes can be a useful synthetic tool for the formation of cyanohydrins, which can then be further transformed into a variety of functional groups. However, the selectivity and yield of this reaction must be carefully considered and optimized for successful synthesis.

5. How does the presence of a catalyst affect the HCN addition to aromatic conjugated aldehydes?

The use of a catalyst can significantly enhance the rate and selectivity of HCN addition to aromatic conjugated aldehydes. Common catalysts include Lewis acids such as AlCl3 or BF3, which can activate the carbonyl group and facilitate the addition of HCN. In some cases, the use of a catalyst may also lead to regioselective or stereoselective addition of HCN to the aldehyde.

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