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Condensation of lignin is believed to interfere with delignification in alkaline pulping processes. The lack of clear evidence motivated us to quantitatively revisit it. This article evaluates the self-condensation of 4-hydroxymethyl-2-methoxyphenol (vanillyl alcohol, Va) in the simplest model system using Va and 2-methoxy-4-methylphenol (creosol, Cr) under the same soda cooking conditions employed in our previous paper. Dimeric and trimeric self-condensation products of Va consisting of the α-5 bond (VaVa, 2-(4-hydroxy-3-methoxybenzyl)-4-hydroxymethyl-6-methoxyphenol), α-1 bond (VaVa’, bis(4-hydroxy-3-methoxyphenyl)methane), and α-5 & α-1 bonds (VaVaVa’, 2,4-bis(4-hydroxy-3-methoxy-benzyl)-6-methoxyphenol) were identified and quantified. The formation rate of VaVa from Va was suggested to be about twice of that of VaVa’, and to be similar to that of the condensation product between the α-carbon of Va and the aromatic C5-carbon of Cr (VaCr), which was identified in the first paper. Among all these detected condensation products, only VaVa that can be converted to the corresponding quinone methide (QM) readily underwent further condensation to be VaVaVa’ and others. Only the monomers (Va and Cr) possessing the small steric factors condense with electrophilic QM’s as nucleophiles. These results suggest that condensation of lignin in actual soda cooking processes, with steric factors much larger than the model system, progresses much less frequently than generally believed.

This study aimed to quantitatively examine how the addition of a strong or weak nucleophile (1.0 mol/L) to a soda cooking treatment (1.0 mol/L NaOH) at 150 °C affects the disappearance and condensation reactions of a simple phenolic lignin model compound, vanillyl alcohol (Va). All the observed phenomena could basically be attributed to the adduct formation of each reagent with the quinone methide intermediate derived from Va (QMVa) and the stabilization of the adduct. The adduct is irreversibly stabilized to be its conjugate base when the reagent was MeNH2 or Me2NH, resulting in the accumulation of the adduct and consequent consumption of QMVa without the reformation of Va from QMVa and condensation reactions of Va with QMVa. The adduct is not stabilized to be its conjugate base and reproduce QMVa when the reagent was Me3N, CO32¯, or SO42¯ (the sodium salt), resulting in the increased concentration of QMVa to promote the condensation reactions of Va with QMVa. These suppressive and promotive effects were more visible in the same treatment of Va with each nucleophile without the addition of NaOH, in which the concentration of hydroxide anion was low.

A phenolic C6-C2-type lignin model compound with the ��-O-4 bond, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)ethanol (I), was acidolyzed in aqueous 82 vol% 1,4-dioxane containing 0.2 mol/L HBr, HCl, or H2SO4 at 85 ��C. It was confirmed that about 15%, 15%, or 60%, respectively, of molecules of compound I do not primarily convert to the enol-ether compound, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)ethene (II), but undergo direct ��-O-4 bond cleavage. This contrasts with our previous result that most molecules of the corresponding non-phenolic compound primarily convert to the corresponding non-phenolic enol ether compound under the same conditions. The disappearance rates of compound I were markedly different between the acidolyses using three acids (HBr > HCl ��� H2SO4), while those of compound II or the ��-methyl-etherified derivative of compound I (III) were not largely different in its acidolysis under the same conditions. These results suggest that the marked difference in the acidolysis rates of compound I originates from the participation of Br��� or Cl���. Acidolysis of the ��-bromo-substituting derivative of compound I (IV) using HBr showed that Br��� adds to the benzyl cation generated from compound I or III to afford compound IV, which consecutively undergoes the HBr elimination to convert to compound II, bypassing direct conversion of the benzyl cation to compound II and resulting in the fast acidolysis.

本研究は、政治的な話題を話すことの抵抗感について検討した。具体的には、日頃話していると想定される9つの話題の中から、より政治的関連性が強い話題を話すことにどの程度抵抗を感じるのか、またその抵抗感を低減する要因も併せて検討した。20代から60代の有権者300名を対象にWeb上で、調査を行ったところ、日常的に話している9つの話題の中では、「国や政府に関する話題」が相対的に最も話すことに抵抗を感じる話題であった。しかし、実際には「国や政府に関する話題」を話す際に感じる抵抗の程度は非常に低いことが示された。また、抵抗感を低減する要因として、ハードな争点的知識が効果を持つ一方で、新聞閲読頻度が抵抗感を高めていることが明らかとなった。, This study examined the freedom to talk about politics by focusing two research questions: (1) How freely Japanese citizens talk about political topics? (2) What factors increase the freedom to talk about political topics? To examine these issues, we conducted Web-based survey to collect discussion network data. The result shows that national government matters relatively scored least free, while respondents felt very-to-somewhat free to talk about political topics. In addition, political knowledge significantly increases the freedom to talk about political subject. However, newspaper use is significantly decreases it. These findings challenge assertions that Japanese citizens talk about political topics guardedly.

The rate-determining step of a C6-C3 dimeric non-phenolic β-O-4 type lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)propane-1,3-diol (veratrylglycerol-β-guaiacyl ether, VG), was evaluated under acidolysis conditions (0.2 mol/l HBr in 82% aqueous 1,4-dioxane at 85°C) by comparing the disappearances between VG and the corresponding compound labeled at the β-position of VG, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)(2–2H)propane-1,3-diol. The disappearance of VG occurred more rapidly than that of the latter compound, and a primary kinetic isotope effect was clearly observed. This result indicates that the C-H bond at the β-position of VG is broken in the rate-determining step. Two possible mechanisms are presented as the rate-determining step: (1) A base abstracts the β-proton of a benzyl cation-type intermediate produced from VG affording an enol ether compound, 2-(2-methoxyphenoxy)-3-(3,4-dimethoxyphenyl)prop-2-en-1-ol; (2) The hydride transfers from the β- to the α-position ...