Condensation reactions of phenolic resins III: self-condensations of 2,4-dihydroxymethylphenol and 2,4,6-trihydroxymethylphenol (1)

This study reexamined the kinetics of the condensation reactions of hydroxymethylphenols with the purpose of elucidating the reaction mechanisms. This report discusses experimental results on the self-condensations of 2,4-dihydroxymethylphenols (2,4-DHMP) and 2,4,6-trihydroxymethylphenol (THMP), focusing on the order of reaction. The relations between the initial rates of reaction and the initial concentrations of reactants were investigated. Results quite different from those of previous reports were obtained. The order of reaction of the selfcondensation of 2,4-DHMP was found to be 1.1, which did not change with the alkali/2,4-DHMP molar ratio. The order of reaction of the self-condensation of THMP was found to vary with both the concentration of THMP and the alkali/THMP molar ratio. In the region of THMP concentrations above 1.5mol/l, the order of reaction was confirmed to be 2.0, which did not change with the alkali/THMP molar ratio. In the region of THMP concentrations below 1.0mol/l, the order of reaction varied with the alkali/THMP molar ratio, showing fractional numbers of 1.2–1.6. These results indicate that unimolecular reaction(s) and bimolecular reaction(s) take place simultaneously as the ratedetermining step in the condensation reactions of 2,4-DHMP and THMP and that the reaction mechanism changes with the species of reactant and, in some cases, with the reaction conditions.Part of this study was presented at the Wood Adhesives 2000 symposium, South Lake Tahoe, Nevada, USA, June 2000     

Condensation reactions of phenolic resins VII: catalytic effect of sodium bicarbonate for the condensation of hydroxymethylphenols

This article describes the catalytic effect of NaHCO₃ on condensation reactions of monomeric hydroxymethylphenols (HMPs) to elucidate the cure-acceleration mechanism. By comparison of the kinetics of self-condensations of HMPs, NaHCO₃ was proved to increase the reactivity of para-hydroxymethyl groups. The changes of ¹³C nuclear magnetic resonance (NMR) chemical shifts on each HMP system with the additive indicated that the addition of NaHCO₃ enhanced some molecular interactions between HMPs and NaHCO₃, facilitating a resonance effect that might play a similar role in dissociation of the phenolic hydroxyl groups of HMPs. In addition, computational modeling by molecular orbital calculations elucidated that hydrogen carbonate anion (HCO ₃ ⁻ ) forms an interaction between either the para-hydroxymethyl group and the phenolic hydroxyl group or between the two para-hydroxymethyl groups of HMPs by hydrogen bonds. From the experimental results, the authors proposed the mechanism of the catalytic action of NaHCO₃: it appears to be due to the delocalization of an electron initiated by the interaction of the para-hydroxymethyl groups and the phenolic hydroxyl of HMPs with HCO ₃ ⁻ through hydrogen bonds, which results in facilitating the formation of active species.     

Curing kinetics of phenol formaldehyde resin and wood-resin interactions in the presence of wood substrates

The curing kinetics of resol PF resin and resin–wood interactions in the presence of wood substrates have been studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The activation energy of cure of PF resin generally increases when PF resin is mixed with wood, mainly due to the decrease of the pH values resulting from the presence of wood. However, wood decreases the curing enthalpy of PF resin through diffusion and the change in the phase of the curing system, which suggests that the curing reactions reached a lower final degree of conversion for the mixtures of PF resin with wood than for the PF resin alone. Moreover, DSC curves and the variation of activation energy with conversion indicate that wood accelerates the addition reactions and retards condensation ones during the curing process of PF resin with wood. The study also revealed that almost no chemical reactions occur between PF resin and wood, but the secondary force interactions of hydroxyl groups between PF resin and wood have been detected. These most significant secondary forces can catalyze the self-condensation reactions of PF resin, although their effect is not vital on the curing kinetics of PF resin.     

Condensation reactions of phenolic resins V: cure-acceleration effects of propylene carbonate

Propylene carbonate (PC) is known as one of the cure accelerators for alkaline phenol–formaldehyde resins. To elucidate the cure-acceleration mechanisms, the effects of PC on the condensation reactions of monomeric hydroxymethylphenols (HMPs) were investigated and compared with those of PC hydrolysate, sodium bicarbonate (NaHCO₃) and ethyl formate. Immediately after the reaction started, PC, decomposing itself simultaneously, accelerated the formation of the ortho-para methylene-bonded dimer of 2,4,6-trihydroxymethylphenol. This effect of PC was very similar to that of ethyl formate. To the contrary, PC hydrolysate accelerated the formation of the para-para methylene-bonded dimer throughout the course of the reaction. This effect of PC hydrolysate was identical to that of NaHCO₃. These results indicate that PC increases the reactivity of the ortho-hydroxymethyl group, presumably through transesterification. On the other hand, NaHCO₃ is formed by the hydrolysis of PC or decomposition of the transesterified HMPs and it increases the reactivity of the para-hydroxymethyl group.     

Kinetics of the hydroxymethylation of phenol I: Rate equation and method of analysis

Seven reactions take place consecutively and competitively during the hydroxymethylation of phenol in aqueous alkaline media. This hydroxymethylation is the first step in the formation of phenolic resins and has long been studied. However, the rate equation, which can describe the seven reactions in those reaction systems where the alkali/phenol molar ratios are <1.0, has not yet been obtained. The authors present a rate equation (in a differential form) for a computer simulation. This equation involves the concentration of hydroxide ion, [OH^–], which changes with the change in the composition of the reaction system and cannot be expressed as a function of reaction time. However, the value of [OH^–] can be obtained by numerical calculation. In the computer simulation the reactions occur for an infinitesimal unit of time, and the changes in the concentrations of formaldehyde, phenols, and hydroxide ion are calculated. The next step of the reaction takes place according to the reaction conditions that result from the previous step. In this manner the reactions progress step by step in a computer. Using this method we can describe the reaction time course, (i.e., the changes in the concentrations of phenol, formaldehyde, and five species of hydroxymethylphenols with the reaction time).Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Kochi, April 1997     

Kinetics of the hydroxymethylation of phenol II: values of rate parameters and results of simulation experiments

The reaction course of the sodium hydroxidecatalyzed hydroxymethylation of phenol was analyzed by use of high-performance liquid chromatography (HPLC), and the rate constants for the seven reactions taking place consecutively and competitively were evaluated by means of a computer simulation technique. Calibration was done at the quantification of the six phenolic monomers from the peak areas in the HPLC chromatogram, taking the differences in molar ultraviolet absorption intensities of the six compounds into account. The values of the energies of activation for the seven reactions obtained differed greatly from those reported by Eapen and Yeddanapalli. Simulation experiments carried out by use of the newly obtained rate parameters showed that the amounts of phenol left unreacted and 2,4,6-trihydroxymethylphenol in the final reaction product increased as the reaction temperature was increased and the alkali/phenol molar ratio decreased. These phenomena can be attributed to the differences in the energies of activation for the seven reactions and differences in the acid strengths of the six phenolic monomers.Part of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998 and at the 1998 annual meeting of the Forest Products Society, Merida, Mexico, June 1998     

Dependence of reaction kinetics and physical and mechanical properties on the reaction systems of acetylation I: reaction kinetic aspects

The dependence of the reaction parameters of acetylation on the reaction mixture was compared among uncatalyzed, acetic anhydride-xylene mixed, and acetic anhydride-pyridine mixed solutions. Wood meal and blocks were used to examine the effect of sample size. A first-order rate equation was applied to the data, and a rate constant and leveling off value of weight gain (WG) were estimated. The rate-determining step was examined from the viewpoint of activation energy. The results were as follows: (1) Regarding the magnitude of the rate constant, the order was pyridine system > uncatalyzed system > xylene system. (2) The ultimate value of WG was lower in the uncatalyzed and xylene systems than the pyridine system, probably because of the swelling ability of pyridine. (3) The activation energies of acetylation estimated for wood meal were 120, 135, and 110kJ/mol for the uncatalyzed, xylene, and pyridine systems, respectively. (4) The characteristics of the diffusion-controlled reaction became marked when the acetylation was carried out in the pyridine system, at elevated temperature, and for wood blocks. Under these conditions, the supply of reagent to the reaction site might not be sufficient to fuel the reaction.Part of this report was represented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

Charcoal affects early development and hormonal concentrations of somatic embryos of hybrid larch

Embryogenic tissue of hybrid larch (Larix x marschlinsii Coaz) was multiplied on Medium M (modified MSG medium supplemented with the plant growth regulators (PGRs) 2,4-dichlorophenoxyacetic acid (2,4-D; 9 microM) and N-6-benzyladenine (2.25 microM)). After 1 week, cultures were transferred to either MSG lacking PGRs (Medium C-) or MSG lacking PGRs but supplemented with 1% activated charcoal (Medium C+). Embryos were sampled after 1 week on Medium M, C- or C+. Embryos were analyzed by ELISA for abscisic acid (ABA), abscisic acid-glucose ester, 2,4-D, indole-3-acetic acid (IAA), indole-3-aspartate (IAAsp), zeatin (Z), zeatin riboside (ZR), isopentenyladenine (iP) and isopentenyladenosine (iPA). Transfer of embryos to Medium C+ reduced the embryo concentrations of 2,4-D and iPA, but resulted in elevated concentrations of IAA, IAAsp, ABA, Z, ZR and iP. Charcoal reduced 2,4-D concentrations of embryos by an order of magnitude greater than PGR-free medium alone. Charcoal affected embryo concentrations of five of the eight PGRs quantified. Use of either C+ or C- medium as part of the maturation protocols also affected germination and plantlet establishment of the embryos. A 1-week treatment on Medium C+ positively influenced plantlet establishment and generally reduced variability during both germination and plantlet establishment.     

Analysis on residue formation during wood liquefaction with polyhydric alcohol

Liquefactions of cellulose powder, steamed lignin, alkali lignin, and their mixtures were carried out to analyze the reaction process of wood using polyhydric alcohol. The liquefaction of wood proceeded immediately and wood components were converted to N,N-dimethylformamide (DMF)-soluble components. After that, the condensation reaction occurred with increasing reaction time. However, none of cellulose powder, steamed lignin, and alkali lignin condensed by themselves during their liquefaction. The mixture of cellulose and lignin was also liquefied, and condensed after a long reaction time. The results of analysis showed that the behavior of the mixture resembled that of wood with respect to molecular weight distribution and the main functional groups. Lignin was converted to DMF-soluble compounds in the initial stage of wood liquefaction, followed by cellulose gradually being converted into soluble compounds. After that, condensation reactions took place among some parts of depolymerized and degraded compounds from cellulose and lignin, and were converted into DMF-insoluble compounds. It was concluded that the rate-determining step of wood liquefaction was the depolymerization of cellulose. Furthermore, it was suggested that the condensation reaction was due to the mutual reaction among depolymerized cellulose and degraded aromatic derivatives from lignin or due to the nucleophilic displacement reaction of cellulose by phenoxide ion.Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

不同种（品种）三叶草愈伤组织诱导及分化影响因素研究

以9个三叶草品种的上胚轴、下胚轴、叶片和子叶为外植体,研究了影响三叶草愈伤组织诱导和再分化的主要因素。结果表明,不同品种不同外植体愈伤诱导率差异较大,下胚轴为较适宜的外植体,其平均愈伤组织诱导率和愈伤分化率为97％和10．3％,改良SH＋2,4-D8．0mg／L＋6-BA0．2mg／L＋KT0．2mg／L为最佳胚性愈伤组织诱导培养基,所形成的愈伤组织的愈伤分化率也最高。     

松实小卷蛾对几种碳烯醛的室内行为反应研究

通过松实小卷蛾雄蛾对(E)-2-癸烯醛、(E)-2-十二碳烯醛、(E,E)-2,4-癸二烯醛和(E,E)-2,4-十二碳二烯醛4个化合物的室内行为反应实验。结果表明,4个化合物都可在一定程度上引起松实小卷蛾雄蛾的兴奋、起飞、定向飞行等反应;松实小卷蛾雄蛾对(E,E)-2,4-癸二烯醛的反应最为强烈,是松实小卷蛾信息素的关键组分,其余3个化合物也是其信息素中不可或缺的组分。能够引起松实小卷蛾雄蛾明显行为反应的最低刺激量为0.01μg。     

陈山红心杉胚性愈伤组织的培养

以未成熟陈山红心杉胚胎为外植体,MS为基本培养基,通过添加不同浓度的6-BA和2,4-D,研究胚性愈伤组织的培养条件.结果表明:2,4-D是胚性愈伤细胞分化和生长的关键因子,最佳培养条件是:MS+6-BA 0.5mg/L+2,4-D 1.0mg/L,继代周期40天左右.     

花椒半硬枝扦插育苗试验

以半硬枝花椒枝条为繁殖材料,就不同药剂种类和浓度,采用5因素5水平正交旋转组合回归设计,进行了花椒半硬枝扦插育苗试验。根据所测得的数据,建立了花椒半硬枝扦插生根率目标函数的回归模型,以及单因素效应和双因素互作效应的子模型。通过计算机模拟仿真筛选出提高花椒半硬枝扦插生根率的综合决策方案,即NAA 98.42~123.99 m g/L;IAA 129.91~161.48m g/L;2,4-D 6.35~7.82 m g/L;B925.91~88.74 m g/L;ABT 76.38~101.77 m g/L。单因子效应的直接评定结果是:ABT生根粉>NAA>2,4-D>B9>IAA;双因子互作生根率较高的组合为IAA和2,4-D组合及IAA和NAA组合。IAA和2,4-D组合,二者在各自的适宜浓度范围内,2,4-D比IAA效果明显;IAA和NAA组合,在一定浓度范围内,选择二者的高浓度组合较好。     

Die Situation im Pflanzenschutz als Problem der Qualitätsforschung

Summary Plant protection as a problem of plant quality-researchThe use of pesticides —although necessary for plant protection — gives rise to cogent criticism. This refers not only to overapplications of biocidal sprays but also to certain pesticides or herbicides themselves being rather suspect as far as their physiological and biochemical behaviour and/or their peculiar metabolism are concerned. This in turn eventually leads to rather a high accumulation of toxic residues of the pesticides or of their metabolites in food plants, the latter sometimes more toxic than the pesticide itself. Furthermore undesired alterations in plant constituents important to health may occur causing significant depressions in levels of ascorbic acid (spinach) and of carotene (carrots). Chemicals used as plantregulators such as 2,4-D and their derivates may cause a most severe detrimental effect to health (damage to the offspring) even when applied in very small concentrations ranging on nanogram-levels. Therefore the dictum of Paracelsus sola dosis facit venenum does not refer to plantregulators such as 2,4-D and related chemicals. Manifold is the propaganda pro agro- chemicals and their use by manufacturers of pesticides. But they are mostly not trustworthy, erroneous and easily to refute by significant facts.     

几种作用因子对多年生黑麦草组织培养影响的研究

以多年生黑麦草成熟种子为外植体进行了愈伤组织诱导和分化的研究。结果表明:dicamba替代2,4 D,蔗糖替代麦芽糖可以显著提高愈伤组织诱导率和植株再生率;在一定的浓度范围内(3～9mg·L-12,4 D)2,4 D浓度的升高可明显提高愈伤组织的诱导率,但同时却降低了分化率;在愈伤诱导培养基中同时使用两种生长激素(2,4 D和NAA)的效果要好于单独使用一种生长激素(2,4 D)的效果;水解酪蛋白、脯氨酸和谷氨酰胺浓度的增加并没有促进植株再生率的升高。     

不同激素配比对油茶花药愈伤组织形成的影响

为了加快油茶品种改良,提高油茶花药愈伤组织的诱导效率,在低温预处理（4℃）的基础上,以MS为基本培养基,研究了不同浓度的2,4-D、NAA及2,4-D、6-BA配比对普通油茶花药愈伤组织诱导效率的影响。结果表明：2,4-D、NAA诱导普通油茶愈伤组织的较优组合为2,4-D0．6mg／L,NAA0．05或0．5mg／L,愈伤组织诱导率分别达到35．56％和24．65％,在油茶花药愈伤组织诱导过程中。2,4-D有利于愈伤组织的形成,是最重要的因素;2,4-D、6-BA的混合使用更有利于愈伤组织的发生,并且两种激素适当的配比是提高愈伤组织诱导率的重要因素,0．5mg／L的2,4-D与0．2mg／L6-BA组合是实验得出的较优水平,愈伤组织诱导率达到42．74％。     

不同激素配比对库拉索芦荟愈伤组织诱导的影响

以MS为基本培养基，添加不同浓度的2，4-D、NAA、KT或其组合，研究库拉索芦荟愈伤组织的诱导及生长情况。结果表明，两种生长素均可诱导出愈伤组织，但较高浓度的2，4-D易导致褐化，而高浓度的NAA诱导出的愈伤组织含水量较高，以两种生长素配合使用再辅以低浓度的KT效果较好，其中15mg/L的KT 4mg/L的2，4-D 0．1mg/L的KT的组合，愈伤组织诱导率达到90％，且愈伤组织生长较旺盛。