正辛醇的γ辐照稳定性及辐解产物分析

在高放射性废液后处理的萃取工艺中,正辛醇被认为是具有应用前景的稀释剂之一,而研究其γ辐射效应对指导其实际应用具有重要意义.本文对N_2环境下γ辐照后的正辛醇进行了紫外-可见(UV-Vis)光谱和傅里叶变换红外(FTIR)光谱研究.结果表明正辛醇在100 kGy以下辐照后化学结构未发生变化,而吸收剂量增至300kGy时有羰基化合物生成.通过色谱(GC)和色质联用(GC-MS)进一步分析了高剂量(600 kGy)辐照后正辛醇的气体及液体辐解产物,发现主要气体产物为H_2,并伴有微量的CO_2和CH_4;主要液体产物为正辛醛,其占未辐解正辛醇的质量百分含量小于1%,并伴有少量正庚烷和8-羟基十五醇.对辐照后正辛醇的化学结构及辐解产物的分析表明,正辛醇在氮气下经γ辐照后,主要发生α碳原子上的C-H键断裂,并伴有β碳原子上的C-C键断裂.此外,抽氢反应也是正辛醇辐解的重要途径.     

Mn(I)催化亚胺和炔烃脱氢偶联反应的机理研究

近年来随着过渡金属催化剂的发展和广泛使用, C—H键的活化成为了有机合成中的一大热点, 尤其是在构建有机化合物C—C键中应用广泛. 作为一种储量较大的廉价催化剂, Mn催化的C—H活化表现出巨大的应用价值和研究潜力. 我们采用密度泛函理论(DFT), 对1,4-二氧六环溶液中Mn活化C—H/N—H键实现[4+2]脱氢环化的反应机理进行了系统的研究. 我们发现该反应的催化循环包括溴负离子辅助的催化剂引发、炔烃的插入、双键迁移成环、β-H消除释放产物异喹啉以及催化脱氢循环的C—H键活化等步骤. 旨在深入理解Mn(I)活化C—H键脱氢气的具体过程, 为更多Mn催化的C—H活化反应提供理论依据.     

硝酸对N,N-二甲基羟胺γ-辐解及液态辐解产物的影响

N,N-二甲基羟胺(DMHA)是用于动力堆乏燃料后处理U与Pu和Np分离的新型无盐还原剂, 本文研究了硝酸对DMHA γ-辐解及液态辐解产物的影响. 研究结果表明: 在U、Pu分离循环和Pu纯化循环的辐照剂量下, 在0.3-1.0 mol·L^-1的硝酸溶液中, 0.1 和0.5 mol·L^-1 DMHA具有较好的辐照稳定性. 当吸收剂量为5-25kGy时, DMHA硝酸溶液的液态辐解产物主要有单甲基羟胺、甲醛、甲酸和亚硝酸. 有机物的浓度远远高于亚硝酸浓度, 且随着剂量和硝酸浓度的增加而增大. 对于相同的硝酸浓度和剂量, 0.1 mol·L^-1 DMHA辐解产生的一甲基羟胺的浓度高于0.5 mol·L^-1 DMHA, 但前者辐解产生的甲醛浓度低于后者; 当硝酸浓度较高时, 0.1 mol·L^-1 DMHA辐解产生的甲酸浓度高于0.5 mol·L^-1 DMHA. 亚硝酸浓度与硝酸浓度及剂量的关系取决于起始DMHA和硝酸浓度.     

γ-旁氏效应及其在立体异构体确定中的应用*

核磁共振碳谱中,碳化学位移受立体结构影响很大。同族原子中,和含相对较小的电负性原子(如Br/I)分子相比,大电负性原子(如F/Cl)会使其相连的α-碳化学位移增大,而β-及γ-碳化学位移更小。多数教材对其解释过于抽象,让学生理解困难。本文通过立体电子效应和位阻效应详细解释了取代基对于β-和γ-碳化学位移的影响。这些影响中,γ-旁氏效应应用最为广泛,常用于确定立体异构体的构型。大电负性原子有助于提高分子中邻位交叉式构象的比例。进而通过空间排斥,使该原子处于γ-位C—H 键的电子云移向碳端,导致σ键中的氢原子去屏蔽而碳原子屏蔽,进而该γ-位C—H键中相应氢化学位移增大,而碳化学位移减小。这种空间排斥更多见于固定环体系,从而可广泛用于立体异构体的结构分析中。此外,还分享了部分文献和本课题组的数据,帮助读者更好地将其运用于教学和科研中。     

辐照气氛对异丙氧基杯[4]冠-6辐解的影响

异丙氧基杯[4]冠-6(1,3-交替-25,27-二(2-丙氧基)杯[4]芳烃-26,28-冠-6, 简称BPC6)对高放废液中的放射性Cs离子具有很好的选择萃取性能, 然而在萃取过程中BPC6 会受到强辐射场辐照, 所以有必要研究其辐射稳定性. 本文应用气相色谱(GC)、傅里叶变换显微红外(Micro-FTIR)和核磁共振(NMR)谱等手段分析了BPC6 固体分别在O₂和N₂气氛下的γ辐照效应. 结果表明, 当剂量为1 MGy时, O₂气氛下BPC6 的辐解率明显高于N₂(分别约为10.4%和2.5%), 而且气体辐解产物也有很大差异, 在O₂气氛下主要为H₂、CH₄、CO和CO₂,而在N₂辐照气氛下还有C₂H₄、C₂H₆、C₃H₆和C₃H₈等产物. 通过综合分析气体与固体辐解产物, 我们提出BPC6在不同气氛下具有不同的辐解途径, 这将为BPC6 萃取体系的辐射效应研究提供新的方法与思路, 加深对其辐解机理的认识.     

γ辐照引发[Cnmim][NTf2]离子液体变色研究

1-烷基-3-甲基咪唑双三氟甲基磺酰胺型离子液体(C_nmim][NTf₂])被认为是最有希望用于核燃料循环中的分离试剂之一, 虽然其化学结构在辐照过程中变化不大, 但在受到γ辐照后会发生明显的变色, 因此有必要研究该类离子液体的变色原因. 本文以⁶⁰Co为辐照源, 系统研究了辐照后不同C(1)－烷基链长和咪唑环上C(2)位上的H被甲基取代后离子液体的紫外-可见(UV-Vis)吸收光谱行为, 并结合辐照后离子液体荧光光谱和质谱的变化, 分析了导致该类离子液体辐照后颜色加深的原因. 结果表明, 随着咪唑环上C(1)―烷基链长度和剂量增大, 离子液体颜色加深; 而C(2)位上的H被甲基取代后颜色明显变浅. 辐照后咪唑型离子液体的变色主要来自于辐照后产生的烷基侧链含双键的咪唑阳离子, 咪唑阳离子二聚体和含氟咪唑化合物. 此外, γ辐照引起咪唑阳离子易发生π-π堆积, 而聚集态含量增加也会引起颜色加深.     

Pd催化甲醇裂解制氢的反应机理

基于密度泛函理论(DFT), 研究了甲醇在Pd(111)面上首先发生O—H键断裂的反应历程(CH3OH(s)→CH3O(s)+H(s)→CH2O(s)+2H(s)→CHO(s)+3H(s)→CO(s)+4H(s)). 优化了裂解过程中各反应物、中间体、过渡态和产物的几何构型, 获得了反应路径上各物种的吸附能及各基元反应的活化能数据. 另外, 对甲醇发生C—O键断裂生成CH3(s)和OH(s)的分解过程也进行了模拟计算. 计算结果表明, O—H键的断裂(活化能为103.1 kJ·mol-1)比C—O键的断裂(活化能为249.3 kJ·mol-1)更容易; 甲醇在Pd(111)面上裂解的主要反应历程是: 甲醇首先发生O—H键的断裂, 生成甲氧基中间体(CH3O(s)), 然后甲氧基中间体再逐步脱氢生成CO(s)和H(s). 甲醇发生O—H键断裂的活化能为103.1 kJ·mol-1, 甲氧基上脱氢的活化能为106.7 kJ·mol-1, 两者均有可能是整个裂解反应的速控步骤.     

基于钯催化的C—H选择性官能团化构建C—C键*

近几十年来,钯催化C—H键的选择性官能团化反应已成为有机合成中构建C—C键的重要策略,基本可以分为三类反应模式：C—H键与芳基或烷基卤化物（或拟卤化物）的交叉偶联反应、C—H键之间的交叉脱氢偶联反应、C—H键与金属有机化合物的交叉偶联反应。本文综述了该领域的最新研究进展,介绍了各类反应的特点、优势及在合成中的应用,提出了今后研究和发展的重点及方向。     

钌催化间位磺化反应机理的DFT研究

导向过渡金属催化反应是实现区域选择性芳环碳氢活化/衍生化的一种重要手段. 本文使用DFT理论(M06//B3LYP)对Frost小组的钌催化2-芳基吡啶间位磺化反应机理进行了研究. 通过计算, 我们发现该机理主要包括邻位C—H活化、亲电取代、还原消除及催化剂再生四个步骤. 其中导向邻位C—H活化是速率决定步, 亲电取代为区域选择决定步. Ru与导向基邻位碳原子成键使苯环电子密度分布发生变化, 同时与位阻作用相结合引导亲电取代发生在Ru—C键的对位(即导向基间位). 在此基础上, 我们还研究了K₂CO₃和溶剂极性对反应的影响.     

黄铁矿在维持高放废物处置库近场还原性环境中的作用

研究了黄铁矿受60Coγ射线辐照后对地下水还原性环境的影响.辐照剂量率为200Gy·min-1,总吸收剂量为5×106Gy.通过分析辐照前后以及与地下水共同辐照后黄铁矿的结构和组成,发现60Co的γ射线可使地下水发生辐解反应,从而将黄铁矿氧化;但无论是直接辐照还是与地下水共同辐照,60Co的γ辐射均不改变黄铁矿的结构.黄铁矿可以消耗地下水辐解产生的氧化性产物,有利于维持处置库近场的还原性环境,提高处置库的安全性.     

Changes in physicochemical and mechanical properties of γ-irradiated polypropylene syringes as a function of irradiation dose

The effect of γ-irradiation on mechanical, thermal, physicochemical and structural properties of polypropylene (PP) syringes was studied. Irradiation doses of 30, 60 and 120 kGy were used with non-irradiated PP syringes serving as control samples. Irradiation caused a significant deterioration in mechanical properties of samples. The compression strength of whole syringe body decreased with increasing irradiation dose. Similarly % extension at break decreased with increasing irradiation dose. Of the physicochemical properties tested, both degree of yellowness and extractable radiolysis products increased with increasing irradiation dose. Melting temperature as well as specific melting enthalpy decreased with increasing irradiation dose. Minor differences in FTIR spectra were observed, mainly in the region of 1720 cm⁻¹, corresponding to the absorption of carbonyl compounds indicating the formation of increased amounts of oxidation products at high irradiation doses. Gas chromatography- mass spectroscopy analysis indicated the formation of a number of radiolysis compounds as a result of irradiation. The number and concentration of these compounds increase progressively with increasing dose until 60 kGy. At the same time a number of compounds initially present in non-irradiated syringes were destroyed by irradiation.     

Spectroscopic analysis of pindolol irradiated in the solid state

Pindolol ((2RS)-(1-(1H-indol-4-iloxy)-3- [(1-metyloetylo)amino]-2-propanol) in substantia was exposed to ionising radiation emitted by high energy electrons from an accelerator, in the standard sterilisation dose of 25 kGy and in higher doses from the range 50–400 kGy. The effects of irradiation were checked by spectrometric methods (UV, MS, FT-IR, EPR) and hyphenated methods (HPLC-MS) and the results were referred to those obtained for non-irradiated sample. EPR results indicated the presence of free radicals in irradiated samples, in the amount of 1.36 × 10¹⁶ spin g^?1 for 25 kGy and 3.70×10¹⁶ spin g^?1 for 400 kGy. The loss of pindolol content determined by HPLC was 1.34% after irradiation with 400 kGy, while the radiolytic yield of the total radiolysis for this dose of irradiation was 2.69×10⁷ mol J^?1. By means of HPLC-MS it was possible to separate and identify one product of radiolytic decomposition, which probably is 2-((R)-3-(1H-indol-4-yloxy)-2-hydroxypropylamino)propan-1-ol formed upon oxidation. In the range of sterilisation doses (25–50 kGy), pindolol was found to show high radiochemical stability and would probably be safely sterilised by the standard dose of 25 kGy.      

DSC and spectroscopic studies of disulfiram radiostability in the solid state

The effect of ionising radiation on the physico-chemical properties of disulfiram (Antabuse, Esperal, bisdiethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accelerator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10–100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that disappears after solution in water or methanol. After the irradiation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC −1.5%, UV −3.6%, iodometric titration method −2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10–50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation.     

Evaluation of protein content, lysine and sulfur-containing amino acids content and electrophoretic patterns of soluble proteins for gamma-irradiated semolina before and after milling of durum wheat

Influenced of gamma irradiation (0, 0.25, 1, 2.5, 5 and 10 kGy) on total nitrogen, lysine and sulfur-containing amino acids content and electrophoretic patterns of soluble proteins of semolina was studied. The effect of irradiation before and after milling on previous parameters was also investigated. Protein content of semolina was not affected with gamma irradiation before and after milling. Up to 10 kGy dose, cystine and methionine were not significantly changed, although they increased slightly with increasing irradiation dose. Lysine content decreased significantly (P≤0.05) at irradiation dose higher than 5 kGy. At 10 kGy dose, lysine decreased 5% and 14% for irradiated semolina and that obtained from irradiated wheat grains, respectively. The bands number and intensity of soluble proteins decreased with increasing irradiation dose higher than 5 kGy, as shown on SDS-PAGE electrophoresis. Irradiated semolina and semolina obtained from irradiated wheat grains at 10 kGy showed 13 and 15 bands, respectively. Unirradiated sample showed 19 bands.     

Radiodegradation of nadolol in the solid state and identification of its radiolysis products by UHPLC–MS method

Nadolol ((2R*,3S*)-5-{[(2R*)-3-(tert-butylamino)-2-hydroxypropyl]oxy}-1,2,3,4 tetrahydronaphthalene-2,3-diol) in substantia was exposed to ionizing radiation generated by a beam of high-energy electrons in an accelerator, in the standard sterilisation dose of 25 kGy and in higher doses of 50 ? 400 kGy. The irradiated and non-irradiated (control) samples were analysed by the infrared spectrophotometry, electron paramagnetic resonance, differential scanning calorimetry (DSC) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC–MS). The irradiated samples were found to contain free radicals in concentrations much higher than that observed for the other irradiated β-blockers. On the basis of UHPLC–MS results, it was possible to establish structures of 11 compounds of the impurities and/or products of nadolol decomposition. The main product of radiodegradation was concluded to be formed as a result of abstraction of the hydroxyl group and aromatization of the tetrahydronaphthalene ring. The results of DSC measurements confirmed the presence of radiolysis products in the irradiated samples of nadolol. A shift of the endothermic peak corresponding to melting towards lower temperatures (by 4.4 °C at the dose of 400 kGy) was directly proportional to the doses of radiation used, which permits concluding that this method is sensitive and suitable for evaluation of radiodegradation of nadolol in solid phase.     

Determination of radiolysis products in gamma-irradiated multilayer barrier food packaging films containing a middle layer of recycled LDPE

Volatile and non-volatile radiolysis products and sensory changes of five-layer food packaging films have been determined after gamma irradiation (5–60 kGy). Barrier films were based on polyamide (PA) and low-density polyethylene (LDPE). Each film contained a middle buried layer of recycled LDPE or 100% virgin LDPE (control samples). Data showed that a large number of radiolysis products were produced such as hydrocarbons, alcohols, carbonyl compounds, carboxylic acid. These compounds were detected in the food simulant after contact with all films even at the lower absorbed doses of 5 and 10 kGy. The type and concentration of radiolysis products increased progressively with radiation dose, while no new compounds were detected as a result of the presence of recycled LDPE. In addition, irradiation dose appears to influence the sensory properties of table water in contact with films.     

Radiolysis study of genistein in methanolic solution

The aim of the present work was to identify products obtained from genistein by ionizing radiation and to enhance the antioxidant properties of genistein through radiation-induced transformation. Genistein dissolved in methanol was irradiated γ-rays at a dose of 100 kGy. NMR and (HR) EI-MS spectroscopy were used to identify radiolysis products (GM1 and GM2). We proposed that CH₂OH may be implicated in the formation GM1 and GM2 during radiolysis of genistein in methanol. The genistein in methanol solution showed higher DPPH radical scavenging activity after γ-irradiation. Then, the antioxidant activities of radiolysis products were evaluated and compared to those of genistein.     

Use of reversed-phase HPLC with solid-phase extraction for monitoring of radiolytic degradation of chlorophenols for environmental protection

The efficiency of radiation induced decomposition of chlorophenols depends substantially on the radiation dose used and the presence of specific scavengers in the irradiated samples. Due to the use of HPLC for decomposition control it was shown, for the first time, that the increase of radiation dose results in gradual elimination of chlorine atoms from the chlorophenols molecules. The efficiency of radiolytic degradation of phenol and chlorophenols was monitored by reversed-phase HPLC. Prior to the chromatography the products of radiolytic degradation were preconcentrated using solid-phase extraction with phenyl columns. The most difficult to decompose is the simple phenol, which is also a product of radiolysis of all chlorophenols. Doses up to 2.0 kGy have not decomposed it completely in experimental conditions used. Degradation of chlorophenols in synthetic aqueous solutions takes place at doses from 0.2 to 2.0 kGy at ppm level of substrates depending on the number of chlorine atoms in molecule, however, for river water matrix containing scavengers such as carbonates or oxygen it requires larger doses.