C~6~0亚甲基衍生物的制备和相关反应的机理

介绍了C~6~0亚甲基衍生物的五种制备方法,详细讨论了相关反应的机理。     

海盐颗粒物表面的NO_2非均相反应

为了深入理解沿海城市大气环境中NO2和海盐颗粒物的非均相反应规律,本研究使用漫反射红外傅立叶变换光谱(DRIFTS)比较研究了0%和20%相对湿度(relative humidty,RH)下NO2在湿海盐颗粒物表面的非均相反应.动力学测量表明硝酸盐的生成对NO2是二级反应,并且0%和20%相对湿度条件下,NO2分子浓度为1.96×1015molcules·cm-3时,反应增长阶段反应摄取系数分别为(5.51±0.19)×10-7和1.26×10-6.结果还显示相对湿度在30%以下时,海盐表面MgCl2·6H2O、CaCl2·2H2O所在点位通过释放结合水和吸附水汽,在海盐表面形成液态水的斑点,增强了反应持续能力.因此氯化钠表面非均相反应的研究可能会低估海盐颗粒物的非均相反应活性.     

Heterogeneous reaction of NO2 with sea salt particles

To understand how NO₂ reacts with sea salt particles in the atmosphere of Mega-cities in coastal zones, the heterogeneous reaction of NO₂ on the surface of wet sea salt was investigated with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC). Kinetic measurements indicated that nitrate formation on sea salt was second order in NO₂ concentration and reactive uptake coefficients were (5.51 ± 0.19) × 10^?7 and 1.26 ± 10^?6 respectively under 0% and 20% relative humidity (RH) at NO₂ molecular concentration of 1.96 × 10¹⁵ mol/cm³. The results showed that liquid water was formed at the site of MgCl₂·6H₂O, CaCl₂·2H₂O on the surface of sea salt and made the reaction more sustainable by releasing hydrated water and absorbing water from air even under a low RH (? 30%). Therefore, pure NaCl particles should not be used to represent sea salt in studies of the heterogeneous reaction with NO₂.     

Preparation and characterization of nanotube Li-Ti-O by molten salt method

Nanotube Li-Ti-O compound with high surface (198.6 m²·g⁻¹) was prepared by a method involving the treatment of nanotube Na₂Ti₂O₅·H₂O in molten LiNO₃ and characterization by means of transmission electron microscopy (TEM), energy-dispersive spectra (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry-differential thermal analysis (TG/DTG). Results show that the nanotube Li-Ti-O compound prepared by this method involves two crystal phases: spinel Li₂Ti₂O₄ and anatase Li_xTiO₂ (x < 0.1). Li⁺ exhibits different Li1s binding energy in the two crystal phases. In ambient air, the Li-Ti-O compound adsorbs water easily, and the chemically adsorbed water is difficult to remove below 400°C. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(12): 2135–2139 [译自: 无机化学学报]     

Preparation and characterization of salt hydrates encapsulated in polyamide membranes

Thermodynamic water activity control is a common technique in organic-phase biocatalysis. This can be accomplished by using the transitions of salt hydrates between their various hydrated forms as a water buffer. While this technique is well established, the use of free salt crystals in the reaction mixture poses numerous problems such as difficult recovery and poisoning of the biocatalyst. This article outlines a novel technique for the encapsulation of such materials which avoids these difficulties. The characterization of the capsules and their use as water activity buffers has also been described. Hydrates of Na₂HPO₄ were encapsulated in a polyamide membrane by interfacial polycondensation (IPC) of sebacoyl dichloride and diethylene triamine soaked onto the surface of the salt crystals. This technique, non-aqueous interfacial polycondensation (NAIPC) circumvents the need for the use of an aqueous phase to supply the polar reactant, the amine, thereby facilitating the encapsulation of water soluble materials. The coatings thus produced have an asymmetric membrane-like structure. A thin, non-porous, layer around the salt crystal supports a superstructure of porous polymer. This composite structure facilitates diffusion of material through the capsule wall and the use of hydrophilic polyamides for encapsulation promotes the transport of water. The capsules produced were between 0.5 and 2.5 mm in size and were of adequate mechanical strength to withstand osmotic pressure differences upto 26 bar and resist attritive forces experienced during their use.     

Preparation and reaction of isomeric formyl-2,1-benzisoxazoles

The novel 4-formyl-2,1-benzisoxazole and 7-formyl-2,1-benzisoxazole were prepared for conversion via the Hantzsch synthesis to 1,4-dihydropyridines. The 4-formyl derivative underwent efficient cyclization to the dihydropyridine while analogous reaction of the 7-formyl compound has proven problematic.     

Solvent and salt effects on reaction of Na amalgam with acrylonitrile and methacrylonitrile

The reaction of acrylonitrile (AN) and methacrylonitrile (MeAN) with Na amalgam was studied in diglyme solution. It was shown that addition of dimethyl sulfoxide (DMSO) increases only the rate of hydrodimerization of AN to adiponitrile, while addition of water increases only the rate of hydrogenation of AN to propionitrile. The proposed mechanism assumes two separate intermediates for these two simultaneous reactions. The reaction of MeAN with Na amalgam was found to be 100 times slower than that of AN. DMSO increases the rate of both the hydrodimerization and hydrogenation reactions via the same intermediate. Addition of quaternary ammonium salts to AN in diglyme has an effect similar to that of DMSO. The salts, however, react at very low concentrations due to accumulation of the cations on the charged amalgam surface. The effect of the size and structure of the quaternary cations was studied and is discussed.     

The reaction of the potassium salt of trinitromethane with acetyl chloride and acetone

Conclusions On reacting the potassium salt of trinitromethane with acetyl chloride in abs acetone acylation of the trinitromethane anion does not occur and the main product of the reaction is 1,1,1-trinitro-2,2-dimethyl-pentan-4-one formed as a result of the addition of trinitromethane to mesityl oxide which arises from acetone in the process of reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2769–2771, December, 1967.     

Double decomposition reaction of sodium salt of phenylhydroxysilane with aluminum sulfate

Conclusions A study was made of the double decomposition reaction of the sodium salt of phenylhydroxysilane with aluminum sulfate and it was shown that insoluble polyaluminophenylsiloxanes are obtained in water-toluene medium, while soluble polyaluminophenylsiloxanes are obtained in water-toluene-acetone medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2834–2836, December, 1976.     

Thiazolinium salt: an efficient catalyst for the Mukaiyama reaction

Mukaiyama aldol reaction between benzaldehyde and Danishefsky diene is promoted by ionic liquid-type salts. Hence, thiazolinium salts have been found to be the most efficient for this transformation. On a mechanistic point of view, only the Mukaiyama process is observed without any hetero Diels-Alder cycloaddition. In some cases, cyclisation of the Mukaiyama adduct occurred without addition of TFA. Interestingly, the thiazolinium catalyst can be recycled at least 10 times without loss of activity.     

Phase-transfer-catalyzed asymmetric Darzens reaction using a new chiral ammonium salt

Catalytic asymmetric Darzens reaction of haloamides is described. A new and easily-prepared bis-ammonium salt derived from BINOL acts as an effective phase-transfer catalyst and efficiently promotes the reaction to give the desired epoxides under quite mild conditions with up to 70% ee.     

Cycloheptyne intermediate in the reaction of chiral cyclohexylidenemethyliodonium salt with sulfonates

Reactions of (R)-4-methylcyclohexylidenemethyl(phenyl)iodonium salt and its 3-trifluoromethylphenyl and 4-methoxyphenyl derivatives (1) with tetrabutylammonium mesylate and triflate were carried out in chloroform at 60 degrees C. The products include (S)-4-methylcyclohexylidenemethyl sulfonate (2) and (R)-5-methylcyclohept-1-enyl sulfonate (3) as well as iodoarene. Reactions of (S)-1 were confirmed to provide the counterpart results. The rearranged triflate (R)-3Tf formed in the reaction with triflate maintains mostly the ee (enantiomeric excess) of (R)-1, while the ee of the mesylate product 3Ms is largely lost. The (13)C-labeling at the exocyclic position of 1 results in the isotopic scrambling of C-1 and C-2 of 3Ms in the mesylate reaction. The degree of the scrambling agrees well with that of the loss of ee of (R)-3Ms obtained from (R)-1, implying that the racemization is not due to the intermediate formation of achiral, primary 4-methylcyclohexylidenemethyl cation. Reaction of 1 with mesylate in the presence of CH(3)OD provided the 3Ms deuterated at the 2-position. When tetraphenylcyclopentadienone was added to the mesylate reaction system, the adduct of the 4-methylcycloheptyne intermediate was obtained in 24% yield, but the normal products 2Ms and 3Ms were still formed. The 3Ms obtained here in a low yield maintains the high ee of 1. These results indicate that the cycloheptyne is an intermediate responsible for the formation of racemic product 3Ms in the mesylate reaction. It is also concluded that the unrearranged products 2 are formed via the competitive pathways of in-plane and out-of-plane S(N)2 reactions.     

Preparation of polyethyleneimine nanogels via photo-Fenton reaction

Photo-Fenton reaction was used to prepare polyethyleneimine nanogels (M-PEIs) from PEI pre-polymer as potential non-viral gene delivery vectors. Competition between crosslinking and scission of PEI pre-polymer in assembled cluster made the size of particles homogeneous. Morphologies of the nanoparticles in every step showed the existence of self-assembly in aqueous solution. The results indicated that the crosslinking of PEI pre-polymer was mainly initiated via hydrogen abstraction by hydroxyl radicals generated in the systems.     

Preparation of water-soluble magnetic nanocrystals using aryl diazonium salt chemistry

A novel and facile methodology for the in situ surface functionalization of Fe(3)O(4) nanoparticles is proposed, based on the use of aryl diazonium salts chemistry. The grafting reaction involves the formation of diazoates in a basic medium. These species are unstable and dediazonize along a homolytic pathway to give aryl radicals which further react with the Fe(3)O(4) NPs during their formation and stop their growth. Advantages of the present approach rely not only on the simplicity, rapidity, and efficiency of the procedure but also on the formation of strong Fe(3)O(4)-aryl surface bonds, highly suitable for further applications.     

Preparation of high-purity straight silicon nanowires by molten salt electrolysis

Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process. Using nickel formate as a metal catalyst precursor, straight silicon nanowires(65–150 nm in diameter) were directly prepared by electrolysis from the Ni/SiO_2 porous pellets with 0.8 wt% nickel content in molten CaCl_2 at900 °C. Benefiting from their straight appearance and high purity, the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 m Ah/g. In addition, the silicon nanowire/carbon composite exhibited excellent cycle performance, retaining 90.38% of the initial capacity after 100 cycles. Whilst further study on the charge storage performance is still ongoing, these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis, which is suitable for large-scale production.     

盐效应对丙酮碘化反应动力学参数的影响

丙酮碘化反应是一个复杂反应,其初级碘化反应阶段,在一定酸度的条件下催化进行,是一个与碘浓度无关的二级反应[1]。本文采用分光光度法测定了丙酮碘化反应在不同的离子强度下的反应速率常数。结果表明,离子强度在小于2·1mol·dm-3的范围内,呈正盐效应。1实验部分1·1仪器和试剂UV-7502PC紫外-可见分光光度计,超级恒温槽(±0·1°C);容量瓶(50mL);移液管(5mL,10mL)。1·9980mol/dm-3丙酮溶液;0·9975mol/dm-3HC l溶液;0·009982mol/dm-3碘溶液;KC l,分析纯。1·2实验原理和方法丙酮初级碘化反应式为[2]CH3 CO CH3+I2H+CH2I OC CH…     

Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction.

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.