Photochemistry of 1-methoxyphthalazine 3-oxide

Irradiation of 1-methoxyphthalazine 3-oxide in cyclohexane at 3500 Å resulted in the formation of phthalimide. On the other hand, irradiation in the presence of maleic anhydride resulted in the formation of 1-methoxynaphthalene-2,3-dicarboxylic acid anhydride. The similar cycloadduct was also observed by irradiation in the presence of benzoquinone. The formation of the cycloaddition products was also observed in acetic anhydride at 60°.     

Spinelle mit substituierten Nichtmetallfeilgittern. II. Herstellung von Einkristallen im System CdCr2(S1−xSex)4

Single crystals of the system CdCr₂(S_1?xSe_x)₄ have been prepared by chemical transport with I₂/AlCl₃ mixtures and by flux growth from solutions in molten CdCl₂.     

Selective and effective fluorination of organic compounds in water using Selectfluor F-TEDA-BF4

[reaction: see text] Selective and effective fluorination of various types of organic compounds performed in water as the reaction medium using 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor F-TEDA-BF4) is reported. 2-Naphthole and 2-methoxynaphthalene were thus transformed to 1,1-difluoro-2(1H)naphthalenone, estrone to 10beta-fluoro-1,4-estradien-3,17-dione, phenyl-substituted alkenes to vicinal fluorohydrins, and various ketones, 1,3-diketones, or beta-ketoesters to corresponding alpha-fluoro or alpha,alpha-difluoro ketones.     

Division problem and partial differential equations with constant coefficients in Colombeau's space of new generalized functions

We study the problem of division in Colombeau's space of new generalized functions in the associated sense: more precisely we solve the equation of the formF·G _p H with adequate assumptions onF. By using the Fourier transformation we construct, by simple methods, the solution in the p-associated sense of a partial differential equation with constant coefficients.     

Effect of the electronic structure of carbon nanotubes on the selectivity of electrochemical functionalization

The functionalization of carbon nanotubes through electrochemical routes is gaining importance due to the high degree of control achievable and the ability to render the tubes with a variety of chemical and biological species. In this article, we report systematic investigations on the grafting of phenyl groups through diazonium coupling onto individual metallic and semiconducting carbon nanotubes both experimentally and theoretically. The results show clearly that by optimizing the electrochemical conditions it is possible to obtain a high degree of selectivity for the coupling of phenyl radicals onto metallic nanotubes. The outlined conclusions have strong implications for the design of strategies for the controlled functionalization of individual single-wall carbon nanotubes.     

An unexpected phase transition during the [2 + 2] photocycloaddition reaction of cinnamic acid to truxillic acid: changes in polymorphism monitored by solid-state NMR

We have detected a phase transition during the progress of the solid-state [2 + 2] photocycloaddition reaction of alpha-trans-cinnamic acid. The reaction was monitored using (13)C CPMAS experiments as a function of irradiation time of the parent alpha-trans-cinnamic acid, which forms the product dimer, alpha-truxillic acid. UV light centered at 350 nm was used for photoirradiation, which is in the "tail" of the absorption band of cinnamic acid. Two different crystal polymorphs of alpha-truxillic acid are observed (P2(1)/n and C2/c) at different stages of conversion of the parent crystal, assigned through (13)C NMR and powder X-ray diffraction. The two polymorphs showed clear, distinguishable patterns in the (13)C NMR spectra: a 2-peak versus 3-peak pattern corresponding to sites on the 4-membered sp (3) hybridized ring in the photoproduct. A phase transition is observed midway through the reaction, which we have assigned to the conversion of the P2(1)/n polymorph to the C2/ c polymorph of alpha-truxillic acid. The packing energy of the resultant mixed crystal of cinnamic acid and truxillic acid changes during the course of the photoreaction, which allows for the C2/c polymorph of truxillic acid to appear. Both phases have been confirmed via X-ray powder diffraction. Two techniques--differential scanning calorimetry and solid-state CPMAS NMR using increasingly fast rotational frequencies--demonstrate that the P2(1)/n phase is metastable.     

Evaluation of separation in gradient elution ion chromatography by combining several retention models and objective functions

In this work, three different methods for modeling of gradient retention were combined with several optimization objective functions in order to find the most appropriate combination to be applied in ion chromatography method development. The system studied was a set of seven inorganic anions (fluoride, chloride, nitrite, sulfate, bromide, nitrate, and phosphate) with a KOH eluent. The retention modeling methods tested were multilayer perceptron artificial neural network (MLP-ANN), radial-basis function artificial neural network (RBF-ANN), and retention model based on transfer of data from isocratic to gradient elution mode. It was shown that MLP retention model in combination with the objective function based on normalized retention difference product was the most adequate tool for optimization purposes.