Would you expect allene, H2 C=C=CH2, to show a UV absorption in the 200 to 400 nm range? Explain

step 1 Would you expect a link to have UV in the range of 400 ,400 nanometers? Absorption, higher than

Would you expect allene, H2 C=C=CH2, to show a UV absorption...

Key Concepts

Electronic Transitions

In organic molecules, electrons in ? bonds can be excited to higher-energy antibonding orbitals (?*). The energy required for such a ? to ?* transition depends on the molecular structure, particularly the gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO). This gap determines the wavelength of light that can be absorbed, with larger gaps corresponding to absorption at shorter wavelengths in the UV region.

Conjugation

Conjugation involves the overlap of p orbitals across adjacent double bonds, which allows electrons to be delocalized over several atoms. This electron delocalization generally lowers the HOMO-LUMO gap, shifting absorption to longer wavelengths. Molecules with extensive conjugation can absorb light in the lower-energy (longer wavelength) part of the UV-visible spectrum, often extending into the visible range.

Cumulated Double Bonds

Cumulated double bonds, as seen in allenes, consist of adjacent double bonds with a shared central atom. Unlike conjugated systems, the p orbitals in cumulated systems are generally oriented orthogonally, which limits effective delocalization. As a result, the electronic transitions in cumulated systems are more similar to those of isolated double bonds, typically requiring higher energy (shorter wavelengths) for ? to ?* transitions.

UV-Visible Spectroscopy

UV-visible spectroscopy is a technique used to study the electronic transitions in molecules by exposing them to ultraviolet and visible light. The absorption spectra obtained reveal information about the energy differences between molecular orbitals. The position and intensity of absorption bands provide insights into how structural features such as conjugation or cumulation influence electronic transitions.

Please give Ace some feedback