in example 3 in toluene 40 parts by volume and aniline 1 part were heated 12 hours at 70 u00b0 petrol was added and the liberated succinamic acid separated the dry acid 1 8 parts was dissolved in acetyl chloride 40 parts by volume boiled for 2 hours and the solvent removed crystallisation of the product from a toluene petrol mixture gave e u03b1 3 4 5 trimethoxyphenyl ethylideneisopropylidene n phenylsuccinimide as pale yellow needles melting point 169 5 u00b0 the compound shows similar photochromic properties to the corresponding e anhydride 3 5 dimethoxyacetophenone 4 2 parts and diethyl isopropylidene succinate 4 9 parts in benzene 20 parts by volume were added to a stirred suspension of sodium hydride 1 part in benzene 100 parts by volume when reaction was complete a small amount of ethanol was added to destroy excess sodium hydride the solvent was removed and the residual oil acidified with hydrochloric acid the resulting half ester 5 parts was hydrolysed with 2 ethanolic potassium hydroxide solution and the diacid precipitated by addition of hydrochloric acid the dried acid 3 5 parts was boiled with acetyl chloride 50 parts by volume for 1 hour and the solvent removed the e and z anhydrides were separated by fractional crystallisation from toluene and light petroleum giving pale yellow crystals m p 146 u00b0 147 u00b0 and 124 u00b0 126 u00b0 respectively which on irradiation at 366 nm turn blue the colour is reversed on exposure to while light e e benzylidene u03b13 4 5 trimethoxyphenylethylidenesuccinic anhydride can be prepared by a similar procedure using 3 4 5 trimethoxyacetophenone and diethyl e.