松脂的催化歧化反应产物的气相色谱-质谱分析

采用气相色谱-质谱技术对松脂的催化歧化新工艺的反应产物进行分析,共分离出45个峰,鉴定出其中的38个化合物,并发现松脂歧化产物中歧化松节油的主要成分为对伞花烃,含量为16.26%;歧化松香的主要成分为脱氢枞酸和氢化树脂酸,其含量分别为41.58%和21.43%。在此基础上对松脂歧化反应过程进行了初步探讨,认为松脂原料中的酸性物质发生分子间氢转移反应,萜烯烃的存在促进了脱氢反应的进行;在树脂酸提供的酸性环境下松脂原料中中性油的主要成分双环单萜烯发生开环异构形成单环单萜烯,单环单萜烯再进行催化脱氢转化为对伞花烃。分析结果表明,直接以松脂为原料进行催化歧化反应可同时获得特级歧化松香和高含量的对伞花烃。     

松香催化加氢过程中树脂酸组成变化的跟踪分析

利用自行改进的DEAE-Sephadex离子交换色谱和气相色谱-质谱-计算机联用(GC-MS-DS)技术研究了在Raney Ni 存在下脂松香催化加氢反应过程中各类树脂酸组成的变化。证实在本实验条件下松香催化加氢过程中的主体反应是树脂酸的二氢化,只伴随少量的四氢化和极少量的脱氢反应。发现在二氢海松酸/异海松酸型树脂酸的分子间存在因双键移位而引起的异构现象。在整个跟踪分析过程中,共检出7种二氢枞酸型树脂酸、5种二氢海松酸/异海松酸型树脂酸及3种四氢树脂酸。     

自制氢化松香主要化学组成的GC-MS法测定

利用自行改进的DEAE－Sephadex离子交换色谱从以玉米松香为原料制备的氢化松香中分离出主要化学组成部分－酸性部分，然后采用DB－5毛细管柱和GC－MS技术对酸性部分进行定性和相对含量测定；共鉴定出6种二氢枞酸型树脂酸，4种二氢海松酸／异海松酸型树脂酸，1种四氢枞酸型树脂酸，2种四氢海松酸／异海松酸型树脂酸；其主要成分为13－二氢枞酸、8－二氢枞酸、13β－7－二氢枞酸、8α，13β－四氢枞酸及8（14）－二氢海松酸等。     

株洲氢化松香主要化学组成的分析

 利用改进的DEAE Sephadex离子交换色谱从株洲氢化松香中分离出主要化学组成部分 酸性部分 ,然后采用DB 5毛细管柱对酸性部分进行气相色谱 质谱 计算机联用分析。共鉴定出 6种二氢枞酸型树脂酸 ,4种二氢海松酸 /异海松酸型树脂酸 ,4种四氢枞酸型树脂酸。其主要成分为 8 二氢枞酸、18 四氢枞酸、13 二氢枞酸、8α ,13β 四氢枞酸、13β 8 二氢枞酸及 8 二氢异海松酸等。     

基于纳米镍催化的松香加氢研究--树酯酸组成的研究

松香的主要成份是枞酸型树脂酸,其因共轭双键的存在而易被氧化,大大降低了其附加值。经氢化后的松香具有抗氧性好、脆性小、热稳定性高、颜色浅等特点,因而广泛应用于胶粘剂、合成橡胶、涂料、油黑、造纸、电子、食品等工业部门[1]。采用催化加氢的方法可使枞酸型树脂酸中的共轭双键消除[2]。以枞酸为代表的反应式为:松香催化加氢主要有熔融法[3]和溶剂法[4],所用催化剂主要是Pd和N i。熔融法制氢化松香,当反应温度低于200℃时,枞酸加氢速度较慢,反应不完全。温度升高,氢化松香中枞酸含量显著地减少,但温度高于250℃时,树脂酸脱羧严重,甚至…     

以Pd/C为催化剂的松香加氢反应机理

松香是由松树分泌的松脂经蒸馏而得,其主要成分为枞酸型树脂酸(C19H29COOH)[1]。由于枞酸型树脂酸含有共轭双键,易与大气中的氧作用,使松香的颜色加深、质变脆、热稳定性差、品级下降。松香经催化加氢反应,改变了枞酸型树脂酸的双键结构,使其趋于脂环的稳定结构,消除了松香因共     

Pd催化木质素醚类二聚体分子内氢转移断裂C—O键研究

结合氢转移方法,研究了木质素模型物2-(2'-甲氧基苯氧基)-1-苯乙醇(1a)分子在无外加氢源的条件下利用金属钯催化剂催化发生C—O键断裂反应.合成并表征了一系列Pd负载型催化剂,通过优化发现反应体系在环己烷溶剂和弱碱添加剂Na2HPO4条件下显示出较好的催化效率.结合反应特点将催化剂进行改进,使用MgO作为载体的催化剂Pd/MgO高效完成了木质素模型物的分子自供氢降解.反应过程可能分为两步进行:首先,模型物在钯表面先进行脱氢过程,含羟基的木质素模型物二聚体1a脱去氢后生成酮式中间体2-(2'-甲氧基苯氧基)-1-苯乙酮(1b),被脱去的氢原子吸附于钯表面.随后,脱氢中间体1b在Pd催化下与其表面吸附的H作用,发生催化C—O键断键过程.     

核磁共振法测定松香中树脂酸总量及枞酸与脱氢枞酸含量

本文用吡嗪作分子间内标，利用氢核磁共振（＾１Ｈ－ＮＭＲ）积分法对松香中枞酸，脱氢枞酸及树脂酸总量进行了测定，并对该方法的可靠性进行了研究和比较，结果令人满意。该法不仅可以克服松香中各异物体及同系物的干扰，而且不必用极难制备和保存的天然纯纵酸和脱氢枞酸作标样。     

氯化锌催化下C60与枞酸的反应

拟利用枞酸分子中的非同环共轭二烯在氯化锌作用下异构化成具有同环共轭二烯的海松酸结构, 再与C₆₀进行Diels-Alder加成反应, 预测可以得到Diels-Alder加成产物. C₆₀、枞酸及氯化锌在邻二氯苯溶剂中, 在氮气保护下于175～180 ℃反应8 h, 将反应物洗涤后进行硅胶柱层析分离, 采用FT-IR, ¹³C NMR, ¹H NMR和MALDI-TOF-MS等分析方法对反应主要产物进行结构测定, 却意外发现得到C₆₀与枞酸的加成过程中发生了脱羧脱氢反应且产物含有芳环的化学结构.     

广东湿地松松脂主要化学组成及其影响因素的探讨

用气相色谱研究了不同地区、不同树龄和不同季节的湿地松松脂的主要组成。研究结果表明,湿地松松脂中松节油含有比对照树种要高得多的β-蒎烯(24.0～46.6％)和低得多的倍半萜烯类(0.6～8.2％;β-蒎烯的含量与湿地松的种植地区和树龄有关,而与采脂季节无关;在广东中部地医种植的具有15年以上捌龄的湿地松含β-蒎烯较高;湿地松松脂中树脂酸组成和含量与采脂季节、种植地区和树龄无关,但枞酸型树脂酸的含量(58～65％)比对照树种低,异海松酸的含量(16～23％)则比对照树种高。     

氢气在松脂和松香中的体积传质系数

高压搅拌釜和计算机数据采集系统，在温度373 K～573 K，压力2.0 MPa～10.0 MPa，搅拌转速600 r/min的实验条件下，根据气体等容吸收降压原理，测定了氢气在松脂和松香中的体积传质系数，并建立了体积传质系数与温度、压力的关联式，为松脂和松香催化加氢反应动力学的研究提供了基础数据。考察了温度、压力对体积传质系数的影响，结果表明体积传质系数随温度和压力的升高而增加。在计算体积传质系数过程中，微分法与积分法二者之间平均绝对偏差为：松脂4.74×10－4，松香1.21×10－4。     

Etude des petits cycles—XXVII : Mecanisme de la regression de cycle des hydrates,hemicetals et cetals des bromo-2 (et tosyloxy-2) cyclobutanones

Solvent effect, common-ion effects and leaving group effects, and kinetic data for the ring contraction of 2-bromo (and 2-tosyloxy) cyclobutanones into cyclopropanecarboxylic acid by water alone, show the slow formation of the hydrate, followed by the fast expulsion of the leaving group in a S_n2 type reaction. The stereochemistry and kinetic data for the thermal ring contraction of 2-bromo-cyclobutanone ketals into cyclopropanecarboxylic esters show an intermolecular halogen transfer and exclude the occurrence of a pericyclic reaction.     

聚苯乙烯热降解机理的理论研究

采用密度泛函理论B3LYP/6-311G（d）方法,对聚苯乙烯（PS）热降解反应机理进行了研究。PS热降解的主要产物是苯乙烯,其次是甲苯、α-甲基苯乙烯、乙苯和二聚体等芳烃化合物。PS热降解反应主要包括主链C-C键均裂、β-断裂、氢转移和自由基终止等反应。针对以上各类反应进行了路径设计和理论计算分析,对参与反应的分子的几何结构进行了优化和频率计算,获得了各热降解路径的标准动力学和热力学参数。计算结果表明,苯乙烯主要由自由基的链端β-断裂反应形成;二聚体主要由分子内1,3氢转移的反应形成;α-甲基苯乙烯由分子内的1,2氢转移后进行β-断裂形成;甲苯由苯甲基自由基夺取主链上的氢原子形成;乙苯由苯乙基自由基夺取氢原子形成。动力学分析表明,苯乙烯形成所需要的能垒低于其他产物形成所需要的能垒,故苯乙烯为主要的热降解产物;这与相关实验结果基本一致。     

Oxygenation of benzyldimethylamine by singlet oxygen. Products and mechanism

[reaction: see text] A product study of the reaction of benzyldimethylamine (1) with thermally and photochemically generated 1O2 in MeCN was carried out. Benzaldehyde and N-benzyl-N-methylformamide are the reaction products, oxygenation representing ca. 9% of the overall quenching of 1O2 by 1. The temperature effect and the intermolecular and intramolecular kinetic deuterium isotope effects were also determined. It is suggested that the products derive from an intracomplex hydrogen atom transfer in a reversibly formed charge-transfer complex.     

Reversible intramolecular hydrogen transfer between cysteine thiyl radicals and glycine and alanine in model peptides: absolute rate constants derived from pulse radiolysis and laser flash photolysis

The intramolecular reaction of cysteine thiyl radicals with peptide and protein alphaC-H bonds represents a potential mechanism for irreversible protein oxidation. Here, we have measured absolute rate constants for these reversible hydrogen transfer reactions by means of pulse radiolysis and laser flash photolysis of model peptides. For N-Ac-CysGly6 and N-Ac-CysGly2AspGly3, Cys thiyl radicals abstract hydrogen atoms from Gly with k(f) = (1.0-1.1 x 10(5) s(-1), generating carbon-centered radicals, while the reverse reaction proceeds with k(r) = (8.0-8.9) x 10(5) s(-1). The forward reaction shows a normal kinetic isotope effect of k(H)/k(D) = 6.9, while the reverse reaction shows a significantly higher normal kinetic isotope effect of 17.6, suggesting a contribution of tunneling. For N-Ac-CysAla2AspAla3, cysteine thiyl radicals abstract hydrogen atoms from Ala with k(f) = (0.9-1.0) x 10(4) s(-1), while the reverse reaction proceeds with k(r) = 1.0 x 10(5) s(-1). The order of reactivity, Gly > Ala, is in accord with previous studies on intermolecular reactions of thiyl radicals with these amino acids. The fact that k(f) < k(r) suggests some secondary structure of the model peptides, which prevents the adoption of extended conformations, for which calculations of homolytic bond dissociation energies would have predicted k(f) > k(r). Despite k(f) < k(r), model calculations show that intramolecular hydrogen abstraction by Cys thiyl radicals can lead to significant oxidation of other amino acids in the presence of physiologic oxygen concentrations.     

Effect of acid density of HZSM-5 on the oligomerization of ethylene in FCC dry gas

The oligomerization of ethylene in FCC dry gas over HZSM-5 catalyst with different Si/Al2 ratios was studied. The effect of acid density of catalyst on the oligomerization of ethylene was discussed. By increasing the acid density of catalyst, ethylene conversion showed a linear increase, while the yields of olefins decreased when the acid density of catalyst exceeded 0.14 mmolNH3/g owing to a promotion of hydrogen transfer reaction. Through comparing the average distance between acid sites on catalyst with kinetic diameters of olefins, it was found that the dimerization of ethylene was not restrained by the sparse distribution of acid sites, while the hydrogen transfer reaction of C3 and C4 olefins was limited. On these bases, a conclusion is proposed that the dimerization of ethylene proceeded via Eley-Rideal mechanism, while the hydrogen transfer reaction of C3 and C4 olefins followed the Langmuir-Hinshelwood mechanism.     

PREPARATION AND PHOTOSENSITIVITY OF WATER SOLUBLE PHENOLIC RESINS CONTAINING ACRYLOYL AND QUATERNARY AMMONIUM CHLORIDE GROUPS

New water soluble and photocrosslinkable prepolymers colltaining acrylate and quaternary ammonium salt groupswere synthesized from epoxy phenolic resin via ring-opening reaction with acrylic acid and with aqueous solution oftriethylamine hydrochloride successively. The second reaction needs no phase transfer catalyst to accelerate, since theproduct formed can act as a phase transfer catalyst. The prepolymer obtained contains both photocrosslinkable acrylategroups and hydrophilic quaternary ammonium salt groups. Optimum conditions for these reactions were studied. Thephotosensitivity of the prepolymer was also investigated. The effects of different photoinitiators, different crosslinkablediluent monomers and amine accelerator on the photosensitivity of the prepolymer were compared. The photoinitiator ofhydrogen abstraction type is still effective without using amine or alcohol as accelerator, because the prepolymer containsα H beside the OH groups formed in the ring-opening reactions     

Kinetics of Transesterification of Methyl Acetate and Ethanol Catalyzed by Ionic Liquid

The kinetic behavior and chemical equilibria for the transesterification of methyl acetate with ethanol to ethyl acetate and methanol catalyzed by an ionic liquid 4‐(3‐methyl‐1‐imidazolio)‐1‐butanesulfonic acid hydrogen sulfate ([HSO₃‐bmim]HSO₄) were studied experimentally. The relationship of chemical equilibrium constants versus temperature was obtained from kinetic experimental data. The effects of temperature, initial molar ratio of ethanol to methyl acetate, and catalyst concentrations were investigated. Based on the reaction mechanism, an ideal homogeneous (IH) and two nonideal homogeneous models (NIH‐1, NIH‐2) were proposed to correlate the reaction kinetic data. The activity coefficient of the catalyst was considered in NIH‐2 but not in the NIH‐1 model. The nonideal homogeneous model NIH‐1 was the best model to describe the kinetics of the transesterification reaction, and the accuracy of the reaction kinetic model is not improved by considering the effects of catalyst on the activities of the reactants and products.