prov:value
| - group, a tolyl group, a halo, such as chlorophenyl group, an alkoxy, such as a methoxyphenyl group, a biphenyl group, or a naphthyl group and the like; R1 to R8 are substituents independently selected from the group consisting of hydrogen, halogen, or hydrocarbon groups, for example from 1 to 10 carbon atoms, and alkoxy groups containing, for example, from 1 to 6 carbon atoms; and X represents an
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