Efficient and Convenient One‐Pot Synthesis of Phosphoramidates and Phosphates

A simple and efficient one‐pot method is described for the synthesis of phosphoramidates/phosphates in excellent yields from dialkylphosphites and trichloroisocyanuric acid in acetonitrile and subsequent treatment with dialkyl amines/alcohols. The procedure is operationally simple, has reduced reaction times, and uses a one‐pot procedure.     

On the electron tunneling in molecules: a generalized orthogonalization procedure for finding tunneling orbitals

A simple method for finding tunneling orbitals of a long-distance electron transfer system is described. The procedure is an approximate biorthogonalization of many-electron donor and acceptor states in which the corresponding orbitals of the system are obtained; one pair of such corresponding orbitals describes the tunneling electron. Usually, the biorthogonalization is performed on the states that describe simultaneously both donor and acceptor complexes and the bridge connecting them, which make the procedure computationally demanding. In this paper a significant simplification of the procedure is proposed. In the procedure, to identify the tunneling orbitals roughly one half of the system is needed--only donor complex, or acceptor complex, plus part of the bridge. The procedure is practically equivalent to biorthogonalization, but computationally much simpler. Applications are illustrated with the results for a model of biological long-distance electron transfer in Ru-modified azurin, and electron transfer involving heme a of cytochrome c oxidase.     

Rapid high-pressure liquid chromatographic analysis of verapamil in blood and plasma

A high-pressure liquid chromatographic assay procedure has been developed for verapamil in blood or plasma. A paired-ion solvent system with a reversed-phase column is employed. The procedure is specific for verapamil and the retention times of the major metabolites are identified. This procedure is sensitive to a lower blood concentration of 1 ng/ml and standard curves were found to be linear up to the highest concentration tested, 500 ng/ml. Several drugs were tested for interference with the assay, but none were found to cause any problems. The procedure is simple, rapid and permits the analysis of up to 25 samples per day.     

High-performance liquid chromatography using a color-forming agent as a mobile phase component. Separation of alkaline-earth-metal cations with arsenazo III and a non-porous gel column

Summary A liquid chromatographic procedure for separating alkaline-earth-metal cations with a non-porous gel column has been developed. Arsenazo III, which is one of the sensitive and commercially available color-forming agents, was used as a component of the mobile phase. Magnesium and calcium could be separated on the nonporous gel column within 55 seconds. The procedure was suitable for the separation of alkaline-earth-metal cations in relatively pure solutions with high sensitivity. Because of its rapidity the described procedure is also potentially applicable for any aqueous sample.     

Determination of calibration function in thermal field flow fractionation under thermal field programming

A new procedure for determining the calibration function able to relate retention and operative parameters to molecular weight of the species in thermal field flow (ThFFF) under thermal field programming (TFP) conditions is presented. The procedure involves determining the average values of retention parameters under TFP and determining a numerical function related to the temperature variations that occur during TFP. The calibration parameters are obtained by a procedure fitting the retention and operative parameters that hold true at the beginning of the TFP. The procedure is closely related to the one previously developed to calibrate the retention time axis under TFP ThFFF and, together, they constitute a full calibration procedure. Experimental validation was performed with reference to polystyrene (PS)-decalin and PS-THF systems. The calibration functions here obtained were compared to those derived by the classical procedure at constant thermal field ThFFF to obtain the calibration function at variable cold wall temperatures. Excellent agreement was found in all cases proving "universality" of the ThFFF calibration concept, i.e. it is independent of the particular system on which it was determined and can thus be extended to ThFFF operating under TFP. The new procedure is simpler than the classical one since it requires less precision in setting the instrumentation and can be obtained with fewer experiments. The potential applications for the method are discussed.     

Microwave-assisted versus conventional decomposition procedures applied to a ceramic potsherd standard reference material by inductively coupled plasma atomic emission spectrometry

Inductively coupled plasma atomic emission spectrometry (ICP-AES) is a powerful, sensitive analytical technique with numerous applications in chemical characterization including that of ancient pottery, mainly due to its multi-element character, and the relatively short time required for the analysis. A critical step in characterization studies of ancient pottery is the selection of a suitable decomposition procedure for the ceramic matrix. The current work presents the results of a comparative study of six decomposition procedures applied on a standard ceramic potsherd reference material, SARM 69. The investigated decomposition procedures included three microwave-assisted decomposition procedures, one wet decomposition (WD) procedure by conventional heating, one combined microwave-assisted and conventional heating WD procedure, and one fusion procedure. Chemical analysis was carried out by ICP-AES. Five major (Si, Al, Fe, Ca, Mg), three minor (Mn, Ba, Ti) and two trace (Cu, Co) elements were determined and compared with their certified values. Quantitation was performed at two different spectral lines for each element and multi-element matrix-matched calibration standards were used. The recovery values for the six decomposition procedures ranged between 75 and 110% with a few notable exceptions. Data were processed statistically in order to evaluate the investigated decomposition procedures in terms of recovery, accuracy and precision, and eventually select the most appropriate one for ancient pottery analysis.     

A simple prototype procedure for cerebrospinal fluid cholesterol determinations

A preliminary procedure for CSF cholesterol is described which can be considered as a prototype method for the special case in which a biological sample is so dilute with respect to all of its constituents that it can be used as the sole diluent for the reactants used to measure the desired constituent in the specimen. Since it would be comparatively simple to generate a fluorophore in place of the chromophore and thereby increase the sensitivity of the procedure, one could easily alter the limits of the determination and/or the size of the sample needed. This is contemplated as a technique which should result from the prototype procedure described. Avenues for the determination of other constituents such as triglycerides or biuret reactive compounds may possibly be accomplished by using a similar determinative approach. Again, in the specific case of cholesterol one may have to resort to detection devices other than colorimetric in order to achieve strong signals for measurement. Fluorescence appears to be a best first approach to attempt in these circumstances for a final procedure based on the suggested prototype.     

An Efficient One-Pot Synthesis of Triamides and Amidodiesters

An efficient one-pot procedure has been proposed for the synthesis of compounds containing three carboxamide groups or one carboxamide and two ester groups. The procedure is based on three-component condensation of alkyl isocyanides with 5-alkylidene- or 5-arylmethylene-substituted Meldrum's acids in the presence of such nucleophiles as phenols and amines.     

Rapid One‐Pot Preparation of 2‐Substituted Benzimidazoles from Esters using Microwave Conditions

A high‐yielding one‐pot procedure for the generation of 2‐substituted benzimidazoles first from esters using a microwave procedure is described.     

Geometrical energy derivative evaluation with MRCI wave functions

The theory of MCSCF and CI energy derivatives with respect to geometrical variations is briefly reviewed with special attention given to the MCSCF and MRCI energy gradients. A computational procedure is proposed for MRCI energy gradients that does not require the solution to any “coupled-perturbed MCSCF ” equations, it does not require any expensive direct-CI matrix-vector products involving derivative integrals, and it does not require any derivative integrals to be transformed from the AO basis to the MO basis. An additional feature is that it does not require any changes to existing MCSCF gradient evaluation programs in order to compute MRCI gradients. The only difference in the two cases is the exact nature of the data passed to the gradient evaluation program from the previous steps in the computational procedure. The additional effort required to compute the entire MRCI energy gradient vector is approximately that required for one additional iteration of the MRCI diagonalization procedure and for one additional MCSCF iteration. For large scale MRCI wave functions, the MRCI energy gradient evaluation should only require about 10% of the effort of computing the wave function itself. This computational procedure removes a major computational botleneck of potential energy surface evaluation.     

A New Preparation of Esters from Carbonyl Compounds Following Lithium Aluminum Hydride Reduction

A modified work-up procedure for the lithium aluminum hydride (LiAlH₄) reduction of esters and other carbonyl compounds is described. The one pot procedure converts an ester to its “homo-reverse ester” and other carbonyl compounds to esters. The key step is trapping the resulting intermediate aluminum alkoxide during reflux with an ester.     

CONVENIENT ONE POT PROCEDURE FOR SYNTHESIS OF FORMYLATED CALIX[n]ARENES

A convenient one pot procedure for obtaining formyl calix [n]arenes via condensation with 1,1-dichloromethylmethylether is described.     

Combining Gold and Palladium Catalysis: One‐Pot Access to Pentasubstituted Arenes from Furan–Yne and En–Diyne Substrates

A series of furan–yne systems was transformed into the corresponding tetrasubstituted annelated phenol derivatives that bear one bromo group. The two‐step procedure consisted of a phenol synthesis and a subsequent electrophilic bromination with N‐bromosuccinimide (NBS). The reactions can be performed in a one‐pot procedure with the same precatalyst. The halogenation reaction is highly selective only in the presence of the gold catalyst. En–diyne substrates were also suitable starting materials; then the pentasubstituted aromatic core showed a completely different substitution pattern for the phenolic products. Furthermore, a one‐pot protocol that consisted of a gold‐catalyzed phenol synthesis, a gold‐catalyzed halogenation reaction, and a palladium‐catalyzed Suzuki coupling was established. The overall efficiency of this procedure was excellent and the substrate scope of the reaction was broad.     

Dénombrement de cascades de colonnes de rectification complexes

A recursive procedure for enumerating separation sequences involving columns with one or two feed streams and several sidestreams is presented in t     

Chemical applications of topology and group theory

Earlier approaches to the analysis of chemical dynamic systems using kinetic logic are refined to deal more effectively with systems having the two or more feedback circuits required for chaos. The essential kinetic features of such a system can be represented by a directed graph (called aninfluence diagram) in which the vertices represent the internal species and the directed edges represent kinetic relationships between the internal species. Influence diagrams characteristic of chaotic chemical systems have the following additional features: (1) They are connected; (2) Each vertex has at least one edge directed towards it and one edge directed away from it; (3) There is at least one vertex, called a turbulent vertex, with at least two edges directed towards it. From such an influence diagram a state transition diagram representing the qualitative dynamics of the system can be obtained using the following 4-step procedure: (1) A logical relationship is assigned at each turbulent vertex; (2) A local truth table is generated for each circuit in the influence diagram; (3) The local truth tables are combined to give a global truth table using the logical relationships at the turbulent vertices; (4) The global truth table is used to determine the corresponding state transition diagram using previously described methods. This refined procedure leads to a more restricted set of influence diagrams having the interlocking cycle flow topology required for chaos than the procedure described earlier. Systems with 3 internal species are examined in detail using the refined procedure. All systems with 3 dynamic variables shown in the simulation studies of Rössler to give chaotic dynamics correspond to influence diagrams which give inter-locking cycle (chaotic) flow topologies by the refined procedure. In addition, two models for the Belousov-Zhabotinskii reaction are examined using the refined procedure. The results are potentially informative concerning possible mechanisms for the limitation of the accumulation of autocatalytically produced HBrO₂ (one of the internal species) during the course of this reaction.     

One‐Pot Synthesis of 2,4,5‐Triphenyl Imidazoles from 1,2‐Diols as Key Reagents

A simple one‐pot procedure for the preparation of 2,4,5‐triphenyl imidazole derivatives is presented. The procedure involves the lead tetraacetate oxidation of 1,2‐diols to give aldehydes in situ , which then undergo a three‐component reaction with benzil and ammonium acetate to yield the imidazole derivatives.     

Comparison between DAX-8 and C-18 solid phase extraction of rainwater dissolved organic matter

Rainwater is a very low concentrated matrix and, for dissolved organic matter (DOM) characterization, an efficient extraction procedure is essential. Isolation procedures based on the adsorption onto XAD-8 and C-18 sorbents have been used in the literature for rainwater DOM isolation, but a comparison between these procedures is lacking. In this work, UV-visible and molecular fluorescence spectroscopies highlighted differences between rainwater DOM isolated by DAX-8 (replacement for XAD-8) and by C-18. It was possible to recover higher rainwater DOM percentage by the C-18 based procedure than by the DAX-8 one. Rainwater protein-like compounds were better concentrated by the C-18 procedure than by the DAX-8 one, while humic-like compounds were similarly concentrated by both procedures. Furthermore, rainwater DOM extracted by the C-18 procedure was more representative of the global matrix, while DAX-8 preferentially extracted humic-like compounds.     

High-performance liquid chromatographic method for determination of ciprofloxacin in biological fluids

A simple and precise high-performance liquid chromatographic procedure has been developed for the determination in biological fluids of ciprofloxacin, a new, with extended antibacterial spectrum, quinoline carboxylic acid. The work-up procedure involves a chemical extraction step followed by isocratic chromatography on a reversed-phase analytical column, with ultraviolet detection. The detection limit for blood levels is 10 ng/ml. The calibration curve is linear from this detection limit to 10 microgram/ml. The statistical analysis of the correlation made between this assay and an agar diffusion procedure during a pharmacokinetic study suggests the existence of one or more active metabolites which could be mainly excreted in the bile.     

Observations of trends for singular values and eigenvectors from library searching ultraviolet-visible spectra with spectral subtraction

A promising procedure for computerized library searching and identification of ultraviolet-visible spectra for one- and two-component mixtures is evaluated. The procedure is based on singular value decomposition and utilizes band position and shape. Searching more than one library spectrum at a time is possible. Library spectra which have similar spectra (collinear) with the sample and each other are indicated by two measures. First, a large condition index must be obtained, and second, two or more large variance-decomposition proportions in the same row need to be associated with the large condition index. The searching procedure has a significant degree of differentiation between the actual sample and potential candidates and is compared with the dot product, Euclidean distance and the correlation coefficient.