Xanthenes

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Tomihiro Nishiyama - One of the best experts on this subject based on the ideXlab platform.

  • COMPARISON OF THE EFFICIENCIES OF THE FUSED HETEROCYCLIC COMPOUNDS, 9H-XANTHENE-2,7-DIOLS, AND RELATED CHAIN-BREAKING PHENOLIC ANTIOXIDANTS
    Bulletin of the Chemical Society of Japan, 1996
    Co-Authors: Tatsuo Yamamura, Takafumi Ishida, Hiroyuki Ueyama, Hirokazu Hayashida, Takuya Ishimaru, Tomihiro Nishiyama
    Abstract:

    The antioxidant activities of 9H-xanthene-2,7-diols that are structurally related to tocopherols and 2,2′-alkylidenedi(hydroquinones) were measured by the inhibition of the thermally initiated autoxidation of tetralin at 60 °C using an oxygen-absorption method. The stoichiometric factors were calculated as n = 3.3—5.5 for 9H-xanthene-2,7-diols and 0.5—0.9 for 2,2′-alkylidenedi(hydroquinones) that lack the fused six-membered heterocyclic ring. Comparison of the alkyl substituent on the bridged methylene carbon showed that 9-methyl-9H-xanthene-2,7-diols increased in n value compared with 9-ethyl-9H-xanthene-2,7-diols. For the 9-methyl-9H-xanthene-2,7-diols, alkyl groups ortho to the phenolic hydroxyl group decreased the Rinh value: two methyl groups by 10-fold, one methyl group by 1.9-fold, and one t-butyl group by 1.4-fold, compared to that for the 9-methyl-9H-xanthene-2,7-diol. On the other hand, 2,2′-alkylidenedi(hydroquinones) were poorer antioxidants than the structurally comparable 9H-xanthene-2,7-dio...

  • 9H-Xanthene-2,7-diols as Antioxidant for Autoxidation of Tetralin
    Bulletin of the Chemical Society of Japan, 1993
    Co-Authors: Tomihiro Nishiyama, Takafumi Ishida, Satoshi Miyazaki, Ryuhei Tsuji, Fukiko Yamada
    Abstract:

    The antioxidant activities of 9H-xanthene-2,7-diols were evaluated by means of an oxygen-absorption method at 60 °C for tetralin. Very good activities were observed for 1,3,4,5,6,8-hexamethyl-9H-xanthene-2,7-diol and 1,3,4,5,6,8,9-heptamethyl-9H-xanthene-2,7-diol.

Fukiko Yamada - One of the best experts on this subject based on the ideXlab platform.

Takafumi Ishida - One of the best experts on this subject based on the ideXlab platform.

  • COMPARISON OF THE EFFICIENCIES OF THE FUSED HETEROCYCLIC COMPOUNDS, 9H-XANTHENE-2,7-DIOLS, AND RELATED CHAIN-BREAKING PHENOLIC ANTIOXIDANTS
    Bulletin of the Chemical Society of Japan, 1996
    Co-Authors: Tatsuo Yamamura, Takafumi Ishida, Hiroyuki Ueyama, Hirokazu Hayashida, Takuya Ishimaru, Tomihiro Nishiyama
    Abstract:

    The antioxidant activities of 9H-xanthene-2,7-diols that are structurally related to tocopherols and 2,2′-alkylidenedi(hydroquinones) were measured by the inhibition of the thermally initiated autoxidation of tetralin at 60 °C using an oxygen-absorption method. The stoichiometric factors were calculated as n = 3.3—5.5 for 9H-xanthene-2,7-diols and 0.5—0.9 for 2,2′-alkylidenedi(hydroquinones) that lack the fused six-membered heterocyclic ring. Comparison of the alkyl substituent on the bridged methylene carbon showed that 9-methyl-9H-xanthene-2,7-diols increased in n value compared with 9-ethyl-9H-xanthene-2,7-diols. For the 9-methyl-9H-xanthene-2,7-diols, alkyl groups ortho to the phenolic hydroxyl group decreased the Rinh value: two methyl groups by 10-fold, one methyl group by 1.9-fold, and one t-butyl group by 1.4-fold, compared to that for the 9-methyl-9H-xanthene-2,7-diol. On the other hand, 2,2′-alkylidenedi(hydroquinones) were poorer antioxidants than the structurally comparable 9H-xanthene-2,7-dio...

  • 9H-Xanthene-2,7-diols as Antioxidant for Autoxidation of Tetralin
    Bulletin of the Chemical Society of Japan, 1993
    Co-Authors: Tomihiro Nishiyama, Takafumi Ishida, Satoshi Miyazaki, Ryuhei Tsuji, Fukiko Yamada
    Abstract:

    The antioxidant activities of 9H-xanthene-2,7-diols were evaluated by means of an oxygen-absorption method at 60 °C for tetralin. Very good activities were observed for 1,3,4,5,6,8-hexamethyl-9H-xanthene-2,7-diol and 1,3,4,5,6,8,9-heptamethyl-9H-xanthene-2,7-diol.

Ayoob Bazgir - One of the best experts on this subject based on the ideXlab platform.

Tatsuo Yamamura - One of the best experts on this subject based on the ideXlab platform.

  • COMPARISON OF THE EFFICIENCIES OF THE FUSED HETEROCYCLIC COMPOUNDS, 9H-XANTHENE-2,7-DIOLS, AND RELATED CHAIN-BREAKING PHENOLIC ANTIOXIDANTS
    Bulletin of the Chemical Society of Japan, 1996
    Co-Authors: Tatsuo Yamamura, Takafumi Ishida, Hiroyuki Ueyama, Hirokazu Hayashida, Takuya Ishimaru, Tomihiro Nishiyama
    Abstract:

    The antioxidant activities of 9H-xanthene-2,7-diols that are structurally related to tocopherols and 2,2′-alkylidenedi(hydroquinones) were measured by the inhibition of the thermally initiated autoxidation of tetralin at 60 °C using an oxygen-absorption method. The stoichiometric factors were calculated as n = 3.3—5.5 for 9H-xanthene-2,7-diols and 0.5—0.9 for 2,2′-alkylidenedi(hydroquinones) that lack the fused six-membered heterocyclic ring. Comparison of the alkyl substituent on the bridged methylene carbon showed that 9-methyl-9H-xanthene-2,7-diols increased in n value compared with 9-ethyl-9H-xanthene-2,7-diols. For the 9-methyl-9H-xanthene-2,7-diols, alkyl groups ortho to the phenolic hydroxyl group decreased the Rinh value: two methyl groups by 10-fold, one methyl group by 1.9-fold, and one t-butyl group by 1.4-fold, compared to that for the 9-methyl-9H-xanthene-2,7-diol. On the other hand, 2,2′-alkylidenedi(hydroquinones) were poorer antioxidants than the structurally comparable 9H-xanthene-2,7-dio...