583
NOTEE18
The photoequilibria obtained were found to be a function ot the wavelength of the exciting light and of the temperature, as reported in other c a s e ~ . ~Figure , ~ ~ 1B shows the absorption spectra of the two isomers of I, as well as the photoequilibrium obtained by irradiation a t 436 nm, at -30" of a solution in a 1: 1 mixture of methylcyclohexane sind decalin. However, this mixture i s a rather poor solvent, and I precipitated below this t ~ w q " t w r e . Quantum yields of the photoisomerization, rind their temperature dependence for compounds I and II Liere therefore measured in 1:l mixtures of rnethylcyclohexane-toluene and l-propanOl-%-~XW~an
