Equilibrium Constants for the Dissociation of Thiourea Adducts of Dialkylnaphthalenes.

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  • SHINDO Takayoshi
    Dept. of Materials-process Engineering and Applied Chemistry for Environments, Faculty of Engineering and Resource Science, Akita University
  • HOSHINO Masahito
    Dept. of Materials-process Engineering and Applied Chemistry for Environments, Faculty of Engineering and Resource Science, Akita University
  • KITABAYASHI Shigeaki
    Dept. of Materials-process Engineering and Applied Chemistry for Environments, Faculty of Engineering and Resource Science, Akita University
  • OZAWA Sentaro
    Dept. of Materials-process Engineering and Applied Chemistry for Environments, Faculty of Engineering and Resource Science, Akita University

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  • ジアルキルナフタレン類のチオ尿素付加物の解離平衡定数

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Abstract

Various 2, 6-dialkylnaphthalenes, 2, 3-dimethylnaphthalene, and 2-methyl-7-t-butylnaphthalene adducts with thiourea were formed to determine the equilibrium constants at temperatures of 273.2 to 303.2K. No adducts of thiourea with 2, 6-dimethylnaphthalene, 2-methyl-6-ethylnaphthalene, and 2-methyl-6-isopropyl-naphthalene were detected at these temperatures. Equilibrium constants of dialkylnaphthalene-thiourea systems, except for the 2-methyl-7-t-butylnaphthalene-thiourea system, were greater than those of the hexadecane-urea system and less than those of isoparaffin- or naphthene-thiourea systems, indicating that stability of dialkylnaphthalene-thiourea adducts is relatively high, whereas n-paraffin-urea adducts are more stable than thiourea adducts with various guest molecules. The order of adduct formation was as follows: 2, 6-di-t-butylnaphthalene>2, 3-dimethylnaphthalene> 2, 6-diisopropylnaphthalene-2, 6-diethylnaphthalene>2-methyl-6-t-butylnaphthalene>2-methyl-7-t-butylnaphthalene. The molar ratios of thiourea to substrate were in the range of 5.0 to 6.7, depending on the size of the dialkylnaphthalenes or bulkiness of the alkyl groups.<br>The formation of the thiourea adducts was exothermic and were favored at lower temperatures. The heats of formation (-ΔHG) were between 28 and 37kJmol-1, which are of the same order of magnitude as those of other thiourea adducts with branched paraffins or cycloparaffins. Deviations were somewhat large, although the values of (-ΔHG) were correlated with m, suggesting that the structure of thiourea adducts is more flexible than that of urea adducts.

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