Question

Calculate the \( \lambda_{\text{max}} \) of the following molecule:

• A. 283 nm
• B. 273 nm
• C. 234 nm
• D. 244 nm

Hint:

- Conjugated systems generally result in longer wavelength absorption maxima (higher \(\lambda _\text{max}\) values). - The larger the conjugation, the lower the energy required for electron transitions, resulting in higher \( \lambda_{\text{max}} \) values.

Answer 1

The Correct Option is B

The \( \lambda_{\text{max}} \), or the maximum absorption wavelength, is an important characteristic of a molecule and is typically determined by its conjugated system, i.e., the extent of \(\pi-electron \) delocalization. The molecule shown in the question contains a benzene ring fused with another six-membered ring, forming a bicyclic structure. In general, the \(\lambda _\text{max}\) of such molecules can be predicted based on their conjugation. The molecule in question has an extended conjugated system, and based on similar structures and their known absorption maxima, we expect the \(\lambda _\text{max}\) for this molecule to be around 273 nm. The given options indicate that 273 nm is the correct maximum absorption wavelength. 

Why Other Options Are Incorrect: - (A) 283 nm: This value is higher than the expected absorption wavelength for this molecule with the given conjugation. 
- (C) 234 nm: This is a typical absorption wavelength for smaller, less conjugated molecules but not appropriate for the given molecule. 
- (D) 244 nm: This is also too low given the structure and expected conjugation. 
Thus, the correct value for \( \lambda_{\text{max}} \) is 273 nm, corresponding to option (B).