What is a double benzene and thiophene nucleus, C8H6S, analogous to naphthalene, and like it the base of a large series of derivatives. [Written also thionaphtene.] called?

thionaphthene — A double benzene and thiophene nucleus, C8H6S, analogous to naphthalene, and like it the base of a large series of derivatives. [Written also thionaphtene.]. (Webster's 1913.)

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