or different and are selected from the group consisting of hydrogen alkyl of one to four carbon atoms inclusive phenyl alkoxy of one to four carbon atoms inclusive nitro trifluoromethyl halogen cyano and equ5 the location of the equ6 groups and r 1 and r 2 are identified as in group a a further group of compounds hereafter referred to as group c are compounds wherein the equ7 groups are located at the 2 and 6 positions or the 3 and 5 positions x and y and r 1 and r 2 are defined as in group b a still further group of compounds hereafter referred to as group d are compounds wherein the location of the equ8 groups are defined as in group c x is hydrogen y is selected from the group consisting of hydrogen alkyl of one to four carbon atoms inclusive alkoxy of 1 to 4 carbon atoms inclusive nitro trifluoromethyl halogen cyano and equ9 r 1 and r 2 are the same or different and are selected from the group consisting of alkyl of seven to ten carbon atoms inclusive cycloalkyl of four to seven carbon atoms inclusive and spc4 wherein p is an integer of 0 to 4 inclusive and s is selected from the group consisting of hydrogen alkyl of 1 to 4 carbon atoms inclusive alkoxy of 1 to 4 carbon atoms inclusive halogen carboxy and cyano with the proviso that when p is zero s is not hydrogen a further group of compounds hereafter referred to as group e are compounds wherein x r 1 r 2 and the location of the equ10 groups are defined.