一道竞赛题的巧解妙法

采用“加减法”求解稠环芳香烃同系物的通式,用“编号法”写出稠环芳香烃的氢化产物的同分异构体.这两种方法可化抽象为具体,化繁难为简易,思路清晰,实用性强.     

环稠卟啉合成的研究进展

利用卟啉大环的碳架组成及其连带成分进行各种环合反应是构建环稠卟啉分子的有效方法. 基于这一合成策略, 概述了近年来通过卟啉分子的结构修饰完成环稠卟啉合成的最新研究进展.     

四种同分异构的四环稠环芳烃的激光等离子体质谱分析

在常规质谱中,各种同分异构的稠环芳香烃基本上无法分辨。但在本文报道的以近红外脉冲激光所产生的等离子体质谱中,所分析的四个四稠环芳香烃尽管分子量相同,其负离子质谱却有十分明显的差异,显示了这一研究方法的结构鉴别能力。     

葫芦脲大环官能团功能化

新型大环化合物的设计与合成一直以来都是超分子化学的研究热点。冠醚、环糊精、杯芳烃和葫芦脲等经典大环分子,以及柱芳烃等新兴大环分子的发展丰富了超分子化学的研究内容。其中,官能团功能化的大环化合物被广泛应用于化学传感器、分子机器、仿生系统、超分子催化、刺激响应体系、功能材料以及药物传递等众多领域。葫芦脲大环具有一个刚性的疏水空腔,由于其独特而优秀的水相识别能力而备受关注。然而,相对于其他大环化合物,葫芦脲由于其官能团功能化难题而发展相当缓慢。近年来,葫芦脲大环官能团功能化的研究获得了巨大的突破,将葫芦脲大环的主客体识别性质从传统的超分子化学拓展到生物化学、材料化学以及药物化学等交叉研究领域。本文重点总结葫芦脲大环官能团功能化现阶段的研究进展,并对其合成方法进行简单明晰的总结与展望。     

溴代稠环芳烃的氧化溴化法合成

以HBr/H2O2为溴化体系,采用氧化溴化法合成了6种稠环芳烃的溴化物。 合成反应无需催化剂,通过控制反应温度和溴化试剂用量,可以在稠环芳烃化合物的活性位选择性地单溴化或双溴化,产率可达51.1%～94.2%。 产品经熔点和1H NMR法确认,合成操作简单安全,环境污染少,有工业应用前景。     

基于C–H活化的炔烃聚合反应合成多功能稠(杂)环聚合物

稠(杂)环聚合物是一类重要的功能聚合物,因其优异的光电特性而被广泛应用于光电领域.这类聚合物的传统制备方法往往需要用到修饰有复杂官能团的稠(杂)环单体,这些单体种类有限且合成难度大,导致稠(杂)环聚合物的发展受到限制. C–H活化过程的发现与提出为利用惰性的C–H键作为潜在官能团提供了可能,有效避免了对单体进行复杂修饰的要求,大大扩增了单体的种类和来源.基于C–H活化的炔烃环化聚合反应,能够在聚合物骨架中原位直接形成稠(杂)环结构,具有原料简单易得、聚合效率高、产物结构丰富等诸多优势,因此受到广泛关注.本文分类总结了基于C–H活化的炔烃环化聚合领域的最新进展,包括合成手段和所得聚合物的性质与功能介绍,并对该领域的未来发展方向进行了展望.     

呋喃稠环类共轭有机分子和聚合物研究进展

目前,噻吩稠环衍生物及相关共轭聚合物作为有机半导体材料已经得到了较多的研究和应用.呋喃作为一种与噻吩杂原子同主族的五元环体系,与噻吩具有类似的化学结构和电子性质,但其具有芳香性更小、载流子迁移率高、荧光量子效率高和溶解性好的特点,得到了越来越多的研究和关注.本综述介绍了呋喃稠环共轭有机分子与呋喃稠环共轭聚合物的合成方法、性质及应用.     

Rh^Ⅱ/Zn^Ⅱ接力催化不对称[4+3]环加成反应

串联环化及环加成反应是合成具有复杂多环骨架化合物的重要手段[1].重氮酰胺类化合物可发生分子内环化生成isomünchnone中间体,作为1,3-偶极子中间体和亲偶极子发生环加成反应,构建含氧桥环骨架的化合物(Scheme1)[2].金属铑(Ⅱ)催化剂能够与重氮酰胺化合物生成铑卡宾中间体,通过羰基官能团分子内进攻铑卡宾生成isomünchnone中间体,然后和双键或叁键发生串联环化反应,形成氧桥环骨架.     

从含有八元环的稠环芳烃到具有负曲率的碳纳米结构:进展与展望

完全由sp²杂化的碳原子所构成的同素异形体呈现出或平坦或弯曲的面,该表面的曲率反映了碳纳米结构的整体几何特性。完全由六元环构成的石墨烯的曲率为零;由六元环和五元环共同构成的富勒烯的曲率为正;向碳原子的六边形网格中引入七元环或八元环则产生形如马鞍的面,其曲率为负。具有负曲率的三维周期性碳结构被命名为马凯晶体或碳施瓦茨体,是碳纳米科学研究长期追寻的目标,然而至今仍未被确定无疑地合成出来。为精确合成具有负曲率的碳纳米结构,一种至下而上的策略是先合成具有负曲率的稠环芳烃,再以其为模板或单体来制备更大的碳纳米结构。具有负曲率的稠环芳烃可以通过向稠环骨架中引入七元或八元环来设计、合成,表现出一些平面稠环芳烃所不具有的结构特征与性质。本文以包含八元环的稠环芳烃为例,介绍具有负曲率的稠环芳烃的设计、合成、立体动力学及其他特征,并展望具有负曲率的碳纳米结构的新研究方向。     

双亲性稠环双卟啉的合成和自组装研究

在稠环双卟啉分子两侧的卟啉环上分别连接亲水和疏水性取代基,合成双亲性稠环双卟啉分子。利用紫外-可见光谱和核磁氢谱考察了它们在不同溶剂中的溶解行为。结果表明,当双卟啉环两侧取代基的亲疏水性差异足够大时,在亲水性溶剂中,两侧取代基溶解性的差异所提供的附加亲疏水作用,可以引导稠环双卟啉分子通过π-π堆积作用形成H-聚集体。这种自组装形成的一维柱状超分子聚集体,在分子光电器件等领域具有潜在的应用前景。     

Capillary GC analysis of diesel fuels using simultaneous parallel triple detection

Diesel fuels from different parts of the UK have been analyzed for polycyclic aromatic hydrocarbons (PAH), nitrogen-containing PAH, and sulfur-containing PAH using capillary column GC with simultaneous parallel triple detection. The concentrations of polyaromatic compounds (PAC) were high and showed considerable variability amongst the fuels. The PAH are mainly naphthalene, fluorene, and phenanthrene and their alkylated homologs; the PANH are mainly carbazole and its methyl derivatives; the PASH are mainly dibenzothiophene and its methyl derivatives.     

A Study On Air Pollution by Asphalt Fumes

Abstract

A TLC/HPLC procedure for the determination of polycyclic aromatic hydrocarbons (PAH), occuring in asphalt fumes (adsorbed on particular matter), is described. The method is based on extraction of asphalt fume particles, collected on glass fibre filters, using CCK₄. Following a clean up step by the aid of a TLC procedure on Al₂ O₃ thinlayer plates, using a mixture of cyclohexane/acetone/ether as the mobile phase. Under UV-light, occuring PAH are indicated as fluorescent spots. A separation of the collected PAH into individual components and their identification is performed by the aid of a HPLC procedure. Futher-more, an approach was made to verify the separated PAH by their fluorescence spectra and their mass spectra.     

Electronic spectra and ionization potentials of a stable class of closed shell polycyclic aromatic hydrocarbon cations

Due to their stability, closed shell polycyclic aromatic hydrocarbon (PAH) cations are possible candidates as carriers for some of the diffuse interstellar bands (DIBs). The electronic absorption spectra and ionization potentials of several closed shell PAH cations are determined in this study. We use density functional theory (DFT) at the BLYP/6-31G* level to determine the ionization potentials and thus confirm the stability of the PAH cations of interest. We use time-dependent density functional theory (TDDFT), again at the BLYP/6-31G* level, to calculate the vertical excitation energies and oscillator strengths of the PAH cations. We observe dominant single absorptions within the DIB spectral region of interest in all of the PAH cation spectra except for the smallest member of the series.     

Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS

Gas chromatography (GC), low-voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.     

Universal Calibration Method for the Determination of Polycyclic Aromatic Hydrocarbons by High Performance Liquid Chromatography with Broadband Diode-Array Detection

Abstract

The response of polycyclic aromatic hydrocarbons (PAH) at different UV wavelengths was measured using high performance liquid chromatography with spectrophotometric diode-array detection. By utilizing the total UV absorption bandwidth (200-400 nm), it was found that a narrow distribution of normalized response factors (area/g) could be obtained for 16 PAH in a reference mixture of frequently-occurring species, even though the PAH represented a wide variety of different chromophores.

Using the mean response factor for the 16 PAH, a universal calibration factor was obtained that formed the basis of a method for the determination of PAH for which calibration data cannot otherwise be obtained. It utilized normal phase high performance liquid chromatography (HPLC) with a cyanopropyl column and a hexane-dichloromethane mobile phase. The HPLC conditions were optimized for the separation of PAH according to their aromatic ring number. The method was developed for the characterization of complex mixtures of fossil fuels-derived PAH that cannot be analyzed by traditional methods. It is applicable to PAH having from 1 to 10 or more fused aromatic rings.     

Determination of polycyclic aromatic hydrocarbons in Athens atmosphere

Concentrations of total suspended particulates (TSP), benzene soluble fraction (BSF) and polycyclic aromatic hydrocarbons (PAH) have been determined in ambient air from four different sites in Athens, situated in urban, semi-industrial and industrial areas. GLC analysis has been applied for the determination of PAH, while the CGC/MS technique was used in order to confirm the obtained results. The same PAH pattern was observed for all stations. The identified PAH have been fluoranthene (FLA), pyrene (PYR), benzo(a)anthracene (BaA), chrysene (CHR), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), benzo(e)pyrene (BeP) and benzo(ghi)perylene (B(ghi)P). The concentrations of individual PAH ranged from traces to 33 ng m-3 (e.g. same or lower comparing to other large cities). The higher values of PAH were found during adverse meteorological conditions.     

Dissociation and multiple ionization energies for five polycyclic aromatic hydrocarbon molecules

We have performed density functional theory calculations for a range of neutral, singly, and multiply charged polycyclic aromatic hydrocarbons (PAHs), and their fragmentation products for H-, H(+)-, C(2)H(2)-, and C(2)H(2)(+)-emissions. The adiabatic and vertical ionization energies follow linear dependencies as functions of charge state for all five intact PAHs (naphthalene, biphenylene, anthracene, pyrene, and coronene). First estimates of the total ionization and fragmentation cross sections in ion-PAH collisions display markedly different size dependencies for pericondensed and catacondensed PAH species, reflecting differences in their first ionization energies. The dissociation energies show that the PAH(q+)-molecules are thermodynamically stable for q ≤?2 (naphthalene, biphenylene, and anthracene), q?≤?3 (pyrene), and q?≤?4 (coronene). PAHs in charge states above these limits may also survive experimental time scales due to the presence of reaction barriers as deduced from explorations of the potential energy surface regions for H(+)-emissions from all five PAHs and for C(2)H(2)(+)-emission from naphthalene--the smallest PAH.     

Determination of PAH in food samples by HPLC with fluorimetric detection following sonication extraction without sample clean-up

A rapid method is proposed for the determination of 16 polycyclic aromatic hydrocarbons (PAH) in non-fatty food (mashed potato, potato and toasted bread samples) based on their extraction with ethyl ether-methylene chloride (1:1) by sonication, and subsequent separation by high-performance liquid chromatography (HPLC) with fluorimetric detection. A Hypersil Green PAH column was used with a gradient of acetonitrile-water as the mobile phase, together with a programme of ten excitation and emission wavelength pairs. At levels 1.60-2320 microg kg(-1), mean recoveries of PAH were in the range 70-86% for mashed potato, potato and toasted bread samples. The relative standard deviations were in the range 4.2-11% (n = 6). Total PAH found in mashed potato were in the range 9.35-17.1 microg kg(-1), in potato samples 8.47-17.2 microg kg(-1) and in toasted bread samples 7.38-18.0 microg kg(-1), with relative standard deviations in the range 0.8-12%. Only chrysene, determined in Ortiz toasted bread (7.38 microg kg(-1)), has carcinogenic properties.     

Dynamics of counterions in polyelectrolyte multilayers studied by electro-optics

The electro-optical behavior of a multilayer constructed via layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) onto ellipsoidal β-FeOOH particles is examined using electric light scattering method. For fully charged polymers (at pH 4.5), the electro-optical effect is found to increase with polyelectrolyte layer number, showing a tendency to saturation in the linear growth regime. The effect is greater and of lower frequency of relaxation for the films ending with PAH in comparison to those with top PSS layer. Evidence is given that polarization of “condensed” counterions along the chains of the last-adsorbed polymer is mainly responsible for the observed electro-optical behavior of the polyelectrolyte multilayer. Although incorporation of “condensed” small ions into the film bulk seems probable for the PSS/PAH multilayer, their participation in the electro-optical effect is found negligible. The structural changes in the PSS/PAH multilayer due to the PAH deprotonation at pH 7.5 and the corresponding changes in the electro-optical effect confirm the key role of the last-adsorbed polymer for the behavior of the entire PSS/PAH film.