ENDOR AND ESR STUDIES OF RADICALS FORMED IN FRIEDEL-CRAFTS REACTIONS

The present study deals with the study of some Friedel-Crafts alkylating system and the accurate measurement of hyperfine coupling constants by ESR and ENDOR techniques. The results indicate that the observed ESR spectra are due to polycyclic aromatic radical cations formed from their parent hydrocarbons.It is suggested that benzyl halides produced in the Friedel-Crafts alkylating reaction undergo Scholl condensation reaction to give polycyclic aromatic hydrocarbons, which were converted into the corresponding polycyclic aromatic radical cations in the presence of aluminum chloride.     

Reaction of hydroxyl radical with aromatic hydrocarbons in nonaqueous solutions: A laser flash photolysis study in acetonitrile

Laser flash photolysis (LFP) of acetonitrile solutions of N-hydroxypyridin-2-thione in the presence of trans-stilbene generates a transient absorbance at 392 nm, attributed to the addition of hydroxyl radical to stilbene. The observed transient absorbance was used in competitive LFP experiments to determine relative rates of reaction for hydroxyl radical with a range of aromatic hydrocarbons in acetonitrile. Structure-reactivity relationships for the reaction of hydroxyl radical with arenes are derived. With these aromatic hydrocarbons, we observe a good correlation between the rates of hydroxyl-radical reaction and the ionization potential of the arene. Kinetic isotope effects are consistent with hydroxyl-radical addition being the dominant reaction pathway with the arene.     

芳烃酰基化后还原制备芳香醇的工艺进展

芳烃制备高附加值精细化学品芳香醇(9-芴甲醇),一直以来存在产物选择性低以及合成成本高等问题。基于此,本文主要综述了芳烃酰基化后还原合成芳香醇的工艺,包括第一步采用Friedel-Crafts酰基化反应、Vilsmeier-Haack反应、Reimer-Tiemann反应、Duff反应等过程将芳烃酰基化合成芳香醛/酮;第二步通过金属氢化物还原、催化加氢还原、活泼金属还原、Cannizarro反应、Meerwein-Ponndorf-Verley还原反应等过程将芳香醛/酮还原合成芳香醇。在总结和归纳各种工艺过程优缺点的基础上,提出了合理的芳香醇制备工艺,为9-芴甲醇产业化制备技术的开发提供帮助。     

Efficiently Aerobic Dehydrogenation of N-Heterocycles and Hydrocarbons over MnAl Oxides

Dehydrogenation of saturated N-heterocycles and hydrocarbons provides an important route to corresponding aromatic compounds. Herein, an efficient and selective MnAlO-catalyzed aerobic oxidative dehydrogenation of five- and six-membered N-heterocycles, imines and hydrocarbons is presented. The reaction features excellent yields of the products, mild reaction conditions, readily available and reusable catalyst. Various N-heterocycles and hydrocarbons can be tolerated by the reaction system and transformed to the corresponding aromatic counterparts. Mechanistic studies revealed that the reaction proceeds mainly through an electron transfer mechanism.     

Early events in radiation chemistry and in photoionization

Real-time studies of aliphatic and aromatic hydrocarbons by pulse radiolysis and laser photoionization reveal the chemistry of the ionic species in the condensed phase. The occurrence of radical cation reactions with solvent molecules provides the core mechanism capable of explaining a wide range of observations in photoionization and radiation chemistry. The study of products and transients in photoionization of aromatic solutes in hydrocarbon and alcohol solvents illustrates several details of this “high-energy” chemistry. A reaction pathway involving ion-molecule reaction of excited ions is indicated for a series of polycyclic aromatic hydrocarbons photoionized using intense excimer laser (248 and 308 nm) pulses in hydrocarbon and alcohol solutions. We have found that condensed-phase ion-molecule reactions in radiolysis are ubiquitous and we speculate on their overall role in hydrocarbon radiolysis.     

Strontium-mediated selective protonation of unsaturated linkage of aromatic hydrocarbons and these derivatives

The selective protonation of aromatic hydrocarbons with at least two or more aromatic rings and aromatic compounds bearing unsaturated linkages can be achieved by metallic strontium metal with ammonium chloride and iodine, or ammonium iodide in tetrahydrofuran. The reaction system is ammonia-free in room temperature and the reaction proceeds high selectivity in moderate to good yields.     

Fenton试剂降解水中的菲和芘

多环芳烃(PAHs)是最早发现且数量最多的致癌物[1],主要来源于人类活动和能源利用过程,如石油、煤等的燃烧、石油及石油化工产品生产、海上石油开发及石油运输中的溢漏等过程.     

Methanol to hydrocarbons: enhanced aromatic formation using a composite Ga2O3-H-ZSM-5 catalyst

Addition of beta-Ga2O3 to H-ZSM-5, as a physical mixture, enhances the formation of aromatic hydrocarbons in the methanol to hydrocarbons reaction.     

Orbital views of the electron transport through heterocyclic aromatic hydrocarbons

Electron-transport properties of heterocyclic aromatic hydrocarbons are investigated with theoretical methods. The present study is based on a previously derived concept for orbital control of electron transport through aromatic hydrocarbons. The orbital control concept provided crucial basic understanding for the best conductance channels in the aromatic hydrocarbons and was successfully applied in the design of molecular devices. That concept was proven to hold true for small aromatic molecules, large polycyclic aromatic hydrocarbons with different edge structures, and in weak and strong coupling with the electrodes junctions. The polycyclic aromatic hydrocarbons and nanographenes used in the molecular electronics are often immobilized with different types of defects, which require the application of the orbital control concept on heterocyclic aromatic hydrocarbons. In this work, the effect of the heteroatoms in aromatic hydrocarbons on their electron-transport properties and the applicability of the orbital control concept on heterocyclic aromatic hydrocarbons are studied. Effective routes for electron transport are predicted in weak coupling junctions by analyzing the phase and amplitude of the frontier orbitals. The qualitative predictions are made with the nonequilibrium Green??s function method combined with the Hückel approximation. Quantitative, first principle calculations are performed with the nonequilibrium Green??s function method combined with density functional theory. The obtained results are in good agreement with the expectations on the basis of the orbital control concept, which proves its applicability in heterocyclic aromatic hydrocarbons.     

New approach to study of spilled crude oils using high resolution GC-MS (SIM) and metastable reaction monitoring GC-MS-MS

Polycyclic aromatic hydrocarbons (PAHs) and geochemical biomarkers are good environmental markers to study the origin and evolution of an oil spill. To have access to the greatest number of molecular ratios, no fractionation of oil into aliphatic and aromatic compounds is made. Three analytical MS approaches are tested to analyze markers in this total hydrocarbon fraction: classical quadrupole GC-MS, high resolution GC-MS (HR GC-MS) and metastable reaction monitoring GC-MS-MS (MRM GC-MS-MS). This analytical approach is used to follow the evolution of PAHs in petroleum polluted mangrove soils over 8 years by using molecular ratios between polycyclic aromatic hydrocarbons and tri- and tetracyclic terpanes.     

Numerical Investigation on 1,3-Butadiene/Propyne Co-pyrolysis and Insight into Synergistic Effect on Aromatic Hydrocarbon Formation

A numerical investigation on the co-pyrolysis of 1,3-butadiene and propyne is performed to explore the synergistic effect between fuel components on aromatic hydrocarbon formation.A detailed kinetic model of 1,3-butadiene/propyne co-pyrolysis with the sub-mechanism of aromatic hydrocarbon formation is developed and validated on previous 1,3-butadiene and propyne pyrolysis experiments.The model is able to reproduce both the single component pyrolysis and the co-pyrolysis experiments,as well as the synergistic effect between 1,3-butadiene and propyne on the formation of a series of aromatic hydrocarbons.Based on the rate of production and sensitivity analyses,key reaction pathways in the fuel decomposition and aromatic hydrocarbon formation processes are revealed and insight into the synergistic effect on aromatic hydrocarbon formation is also achieved.The synergistic effect results from the interaction between 1,3-butadiene and propyne.The easily happened chain initiation in the 1,3-butadiene decomposition provides an abundant radical pool for propyne to undergo the H-atom abstraction and produce propargyl radical which plays key roles in the formation of aromatic hydrocarbons.Besides,the 1,3-butadiene/propyne co-pyrolysis includes high concentration levels of C3 and C4 precursors simultaneously,which stimulates the formation of key aromatic hydrocarbons such as toluene and naphthalene.     

Acetoxylation at benzylic positions of tetrahydrobenzo rings with DDQ in acetic acid

Good-excellent yields of ironoacetoxy derivatives at benzylic positions are obtained upon reaction of polycyclic aromatic hydrocarbons (PAH) containing an angular tetrahydrobenzo ring with DDQ in acetic acid.     

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。     

Anion radicals and dianions as electron transfer reagents

The catalytic regeneration of depolarizers by certain substrates has been demonstrated by means of cyclic voltammetry. As depolarizers we have employed anion radicals of aromatic hydrocarbons, heteroaromatic compounds, ketones, esters, nitriles, and olefins, and dianions of aromatic hydrocarbons, heteroaromatic compounds, ketones, and esters. As substrates we have investigated simple aromatic and aliphatic halides, 1,2- and 1,3-dihalides, carbon dioxide, and activated olefins. A requirement for the observation of a catalytic wave is that the reduced substrate undergoes a practically irreversible reaction after the reaction with the reduced depolarizer; for simple halides it is a cleavage reaction, for 1,2- and 1,3-dihalides an elimination, for carbon dioxide an addition, and for activated olefins a coupling. Electrochemical investigations of these kinds of reactions may be of interest in connection with the mechanism of several types of reactions in organic chemistry.     

Reaction of difluoro- and fluorochloronitroacetic acids with mercuric oxide

Conclusions The reaction of difluoronitroacetic acid with mercuric oxide in aromatic hydrocarbons proceeds by mercuration of the aromatic ring and formation of arylmercury salts of difluoronitroacetic acid. Aryl derivatives of mercuric chloride are obtained in the case of fluorochloronitroacetic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2790–2792, December, 1985.     

A highly selective cascade approach to diverse aromatic ring systems from simple aromatic aldehydes and propiolates

[reaction: see text] A new triethylamine-catalyzed cascade reaction of aromatic aldehydes with propiolates has been developed. This serial multi-bond-forming process furnishes diverse polycyclic aromatic hydrocarbons, including naphthalenes, phenanthrenes, benzofurans, and 2,3,9,9a-tetrahydronaphtha[2,3-b]furans. The chemical outcome of the process depends on the reaction temperature and can be tailored selectively by an appropriate choice of experimental conditions.     

几种固态芳烃与银离子配合物形成常数的测定

作者曾报道用溶质蒸气循环方式制备液态芳烃的饱和溶液,测出苯、甲苯、二甲苯、卤代苯等液态芳烃在水和硝酸银体系中的溶解度,并计算了上述芳烃与Ag~+配合物的形成常数。 具有C=C双键的许多固态芳烃也象液态芳烃一样可与银离子形成配合物,我们设计了溶质蒸气循环方式制备固态芳烃的装置,该法的最大特点是固态溶质和溶剂不直接接触,可以避免固态溶质颗粒在溶剂中的分散和容器壁上的吸附现象,因此用本法测定的溶解度和配合物的形成常数数据可靠、精确。     

Synthesis,Properties, and Packing Structures of Corannulene‐Based π‐Systems Containing Heptagons

Introduction of heptagons into hexagonal carbon lattices can generate negatively curved polycyclic aromatic hydrocarbons, which are of significant interest in the field of exotic molecular nanocarbons. We have successfully synthesized and characterized corannulene‐based π‐systems containing heptagons ( 4 and 5 ) as new negatively curved polycyclic aromatic hydrocarbons as well as possible intermediates in the synthesis of warped nanographene 1 . The formation of 4 and 5 represents the first example for which a heptagon is formed under Scholl reaction conditions before all hexagons are formed. Even more interestingly, we discovered that the mode and degree of solid‐phase intermolecular π–π interaction can be altered significantly by the degree of ring closure.     

Binary system organic base-anode in the oxidative activation of hydrogen sulfide

Initiation of the reaction between hydrogen sulfide and aliphatic, aromatic, and heteroaromatic hydrocarbons in acetonitrile using the binary system organic base-anode is described. The reaction of hydrogen sulfide with nitrogen-containing organic bases is studied by means of cyclic voltammetry. The reaction of hydrogen sulfide with triethylamine leads to the formation of thiolate anion. The next step o reaction is electrochemical oxidation of the thiolate anion that to lead thiyl radical formation in situ thiyl radicals. In the presence of binary system on the basis of hydrogen sulfide aliphatic, aromatic, and heteroaromatic thiols and sulfides are formed at room temperature.     

A density functional theory study on the decomposition of aliphatic hydrocarbons and cycloalkanes during coal pyrolysis in hydrogen plasma

To get deep understanding of the reaction mechanism of coal pyrolysis in hydrogen plasma, the decomposition reaction pathways of aliphatic hydrocarbons and cycloalkanes, which are two main components in volatiles from coal, were investigated. Methane and cyclohexane were chosen as the model compounds. Density functional theory was employed, and many reaction pathways were involved. Calculations were carried out in Gaussian 09 at the B3LYP/6-31G(d,p) level of the theory. The results indicate that the main pyrolysis products of methane and cyclohexane in hydrogen plasma are both hydrogen and acetylene, and the participation of active hydrogen atoms makes dehydrogenation reactions more favorable. H2 mainly comes from dehydrogenation process, while many reaction pathways are responsible for acetylene formation. During coal pyrolysis in hydrogen plasma, three main components in volatiles like aliphatic hydrocarbons, cycloalkanes and aromatic hydrocarbons lead to the formation of hydrogen and acetylene, but their contributions to products distribution are different.