Question

Which type of transitions are responsible for the R-band?

• A. $\pi \rightarrow \pi^$
• B. $n \rightarrow \pi^$
• C. $\sigma \rightarrow \sigma^$
• D. $n \rightarrow \sigma^$

Hint:

R-band = $n \rightarrow \pi^$ transition (especially in carbonyls).

Answer 1

The Correct Option is B

The R-band (or n to $\pi^$ transition) arises when a non-bonding electron is excited to an antibonding $\pi^$ orbital. It is commonly observed in carbonyl-containing compounds and is characteristic of UV-visible spectra.