1. Compare the absorption spectrum of9,10-DAP in heptane with that in alcohol. T
ID: 1076482 • Letter: 1
Question
1. Compare the absorption spectrum of9,10-DAP in heptane with that in alcohol. Two absorption systems should be evident in both absorption spectra. These two absorption systems correspond to excitations from wavelength) absorption system shifts to longer wavelength and broadens while the first absorption (longer wavelength) system shifts to shorter wavelength and exhibits no vibrational structure. In fact the long Based on these shifts, what is the likely nature of the long wavelength absorption system, and what is theExplanation / Answer
When we change the solvent from heptane to alcohol that is as we move from non polar to polar solvent there occurs a change in the wavelength of absorption . This is because of more stabilization of either the ground state or excited state due to hydrogen bonding .
In case of n to pi star transition , in polar solvent ground state gets more stabilised and therfore it's energy decreases and hence the energy gap between the ground and excited state increases and wavelength of transition decreases called as blue shift or hypochromic shift.
In case of pi to pi star transition, excited state I.e pi star star gets more stabilised dhe to H bonding and hence comes down and the energy gap decreases and therefore wavelength increases called as red shift or bathochromic shift.
Due to stabilization of n state I.e non bonding electrons peak absorbance is reduced.
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