Question

Which molecule absorbs at the longest wavelength 1 3-hexadiene or 1 4-hexadiene?

Answer 1

1,3- Hexadiene absorbs at the longest wavelength than 1,4 Hexadiene.

1. This is because of 1,3- Hexadiene is a conjugated molecule that undergoes conjugation, which is not visible in 1,4-Hexadiene.

Answer 2

Answer:

1,3 hexadiene absorbs at the longest wavelength.

Explanation:

1,3 hexadiene absorbs at a longer wavelength as it contains conjugated double bonds. Conjugation in a molecule leads to electron delocalisation. As the delocalisation increases, the spectrum shifts to a longer wavelength.

The conjugated system absorbs the longest wavelength as in such a system, the energy gap for π-π* transition is smaller than the systems which do not possess conjugation. So, less energy is required to cause the excitation of electrons to a higher energy level.

1,4 hexadiene is not a conjugated molecule.