The effect of hydrogen bonding on the electronic spectra of organic molecules

1. The effect of hydrogen bonding upon the spectra of ionic and non-ionic compounds is examined. 2. It is found that: a. when hydrogen bonding increases the polarity of the solute molecule, the absorption spectra moves to longer wavelengths, and b. when the polarity of the molecule is decreased the absorption spectra tends to move to shorter wavelengths. In both cases the extent being determined, in part, by the effect of solvent polarity. 3. The "blue-shift" of the Merocyanines in solvents of high polarity (which can hydrogen bond) can be explained by a reduction in solute polarity caused by solute-solvent hydrogen bonding. 4. The structure of the sydnones is discussed in relation to the movement of their absorption spectra in hydrogen and non-hydrogen bonding solvents.