Some Further Investigations into the Fading Rates of Monoazo Dyes

The fading rates of a aeries of simple monoazo dyes have been investigated with a view to assessing the effect of substituent groups on light fastness. Work reported previously has been checked and extended by the inclusion of dyes with etectrophilic substituent groups. The linear relation between destruction efficiency and the Hammett δ value for the substituent group previously reported has been found to be slightly in error and has been modified accordingly. Possible reaction mechanisms are discussed.