Effect of conjugation in the frequency of absorption of carbonyl group for cinnamaldehyde and benzaldehyde as compared to n-butyraldehyde?

Answer 1

Aldehydes are highly reactive and participate in many reactions.[8]" From the industrial perspective, important reactions are condensations, e.g. to prepare plasticizers and polyols, and reduction to produce alcohols, especially "oxo-alcohols." From the biological perspective, the key reactions involve addition of nucleophiles to the formyl carbon in the formation of imines (oxidative deamination) and hemiacetals (structures of aldose sugars).[8]

Answer 2

Conjugation in cinnamaldehyde and benzaldehyde lowers the energy of their π-electron systems, leading to a redshift in their absorption frequency compared to n-butyraldehyde, which lacks conjugation. This redshift occurs because conjugation delocalizes the π-electrons, making them less energetic and requiring less energy to excite.