Abstract
The magnetic circular dichroism (MCD) spectra of 30 mono-substituted naphthalenes were measured for the 1Lb and 1La absorption bands. It is demonstrated that these spectra can be classified into three groups, and that the sign of the MCD for the 1Lb band is negative if the compound has a donor group and is positive if it has an acceptor group, and that the magnetic rotational strengths are larger for the 1-than for the 2-substituted naphthalenes. This remarkable feature is interpreted in terms of the energy difference between the 1Lb and 1La states and the angle between the electric dipole moments induced by the two transitions, assuming that the mixing of the above two states is dominant in the MCD in these cases. Using the above-mentioned observation, the MCD spectra can be used in analytical chemistry to identify the isomers of mono-substituted naphthalenes and to determine the kinds and characteristics of the substituents.
