Knowledge Bank

“The $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}LA\leftarrow \mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A$ (2100 \AA) and $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}LA,\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}LB\leftarrow \mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A$ (1800 \AA) bands of anisole and its o,$o1$-alkylated derivatives are reported. It is shown that the “classical” case of the spectra of o and o,$o1$ substituted N,N-dimethylanilines representing the effect of twisting of a $\pi$;-orbital into a $\sigma$-orbital is anomalous. This probably results from benzene analogue-charge transfer state interaction. The anisoles, on theoretical grounds, are suggested to represent the “normal” case of intramolecular twisting effects on $\pi \to \pi \ast$ spectra. Low temperature absorption data are reported for both DMAs and anisoles and are interpreted in terms of the steric potential curves arising from o and $o,o1$ substitution.”