nally substituted with one or more halogen atoms, and wherein if the aryl group is phenyl or naphthyl then the phenyl or naphthyl may be optionally substituted with C1 -C4 alkyl, up to C4 alkenyl or C1 -C4 alkoxy, provided that at least one of R3, R4 and R5 is a methyl group substituted with one, two or three halogen atoms; and (3) a solvent. 5.