Question

Acetaldehyde has absorption signals at 160, 180 and 290 nm What type of transitions are responsible for each of these absorptions?

Answer 1

The first absorption band in acetaldehyde corresponds to the one-photon S1 ← S0 transition (290 nm).

The appearance of a strong absorption at 1660–1770 cm⁻¹ in the infrared spectrum of a compound is a clear indication of the presence of a carbonyl group.