Optical sensing of HCl with phenol red doped sol-gels

A dye doped sol-gel for the sensing of hydrochloric acid in solution and/or gaseous phase is described. The sol-gel is obtained by acidic hydrolysis of tetraethoxysilane (TEOS) and phenyltriethoxysilane (Ph-TriEOS) in the presence of phenol red (PR) and further spin-coating onto glass slides. The sensitive response is based on an increase of the absorption band at 510 nm of phenol red entrapped in the sol-gel casting when exposed to HCl solution or gas, due to protonation of the dye. The detection limit of the sol-gel response to moisturized gaseous HCl is below 12 ppm, and its response to HCl in solution falls in the range of 0.01-6 M. The sol-gel coating has a response time of less than 40 s in steady-state, and life-time of more than a year. Weak acids such as acetic acid, benzoic acid, salicylate acid, citrate acid, and carbonic acid do not interfere the response. The responses in acid solutions are completely reversible. In the gaseous phase, response of HCl appears to be moisture sensitive.     

Prediction of the bubble point pressure for the binary mixture of ethanol and 1,1,1,2,3,3,3-heptafluoropropane from Gibbs ensemble Monte Carlo simulations using the TraPPE force field

Configurational-bias Monte Carlo simulations in the Gibbs ensemble using the TraPPE force field were carried out to predict the pressure–composition diagrams for the binary mixture of ethanol and 1,1,1,2,3,3,3-heptafluoropropane at 283.17 and 343.13 K. A new approach is introduced that allows one to scale predictions at one temperature based on the differences in Gibbs free energies of transfer between experiment and simulation obtained at another temperature. A detailed analysis of the molecular structure and hydrogen bonding for this fluid mixture is provided.     

2-Amino-3-picolineN-oxide complexes formed from various copper(II) Salts

Summary Copper(II) complexes of 2-amino-3-picolineN-oxide (3 MA) have been isolated as perchlorate, tetrafluoroborate, nitrate, chloride and bromide salts, and characterized by spectral methods (i.e., i.r., u.v.-vis and e.s.r.). Variation of the ligand to copper(II) salt ratio yielded solids having the following empirical formulas: Cu(3 MA)₄X₂ (X = ClO₄, BF₄ or NO₃), Cu(3 MA)₂X₂ (X = NO₃, Cl or Br) and Cu(3 MA)X₂ (X = Cl). In addition, a deprotonated ligand complex, Cu(3 MA-H)₂, was prepared by treating an aqueous slurry of Cu(3 MA)₄(ClO₄)₂ with NaOH. This complex is considered to be square planar, but does associate to form a dimer in nonpolar solvents such as CHCl₃. The complexes involving coordinated anions appear to be polymeric and to contain halogen orN-oxide oxygen bridging ligands.     

Syntheses using isoxazoles—V: The rearrangement of phenylhydrazones of 4,5,6,7-tetrahydro-4-oxo-isoxazolo[2,3-a]-pyridinium bromides

Rearrangement of the phenylhydrazone (6) and the 2,4-dinitrophenylhydrazone (7) from 4,5,6,7-tetrahydro-4-oxo-isoxazolo [2,3-a]pyridinium bromide (1), by boiling acetic anhydride, gave the 1-(N-anilino)pyrrolo[3,2-b] pyridinones, (9,12 and 13). and the pyrazolo[4,3-b]pyridine-3-carboxaldehyde (8) or its diacetate (11).     

Direct Access to β‐Fluorinated Aldehydes by Nitrite‐Modified Wacker Oxidation

An aldehyde‐selective Wacker‐type oxidation of allylic fluorides proceeds with a nitrite catalyst. The method represents a direct route to prepare β‐fluorinated aldehydes. Allylic fluorides bearing a variety of functional groups are transformed in high yield and very high regioselectivity. Additionally, the unpurified aldehyde products serve as versatile intermediates, thus enabling access to a diverse array of fluorinated building blocks. Preliminary mechanistic investigations suggest that inductive effects have a strong influence on the rate and regioselectivity of the oxidation.     

Structural and rate studies of the formation of substituted benzynes

The key elimination step for the formation of 3-substituted and 3,6-disubstituted benzynes from 2-haloaryllithiums displays a pronounced solvent-dependent regioselectivity. All 2-haloaryllithiums with electron withdrawing groups in the 6 position are shown by 6Li and 13C NMR spectroscopic studies to be monomers in THF. DFT computational studies implicate trisolvates. Rate studies reveal that LiF eliminates via monomer-based pathways requiring THF dissociation whereas LiCl eliminates via nondissociative pathways. Elimination to form 3-chloro- and 3-fluorobenzyne from 2-chloro-6-fluorophenyllithium displays a pronounced solvent-dependent regioselectivity that is traced to competing solvent-dissociative and nondissociative dissociative pathways for the elimination of LiCl and LiF, respectively.     

Hydrothermal Synthesis and Crystal Structure of a New Polyoxovanadate： [Mn（en）3]2en0.5[HV8VV8IVO38（CI）]·4.5H2O （en = Ethylenediamine）

A new compound has been synthesized under hydrothermal conditions and characterized by IR, elemental analysis, XPS and single-crystal X-ray diffraction analysis. The title compound [Mn（en）3]2en0.5[HV8VV8IVO38（CI）]·4.5H2O crystallizes in monoclinic, space group C2/c, with a = 17.016（4）, b = 18.858（4）, c = 18.872（4） A, β = 93.667（4）°, V = 6043（2）A3, Z = 4, Dc = 2.242 g/cm3, Mr = 2040.12, F（000） = 4020,μ = 2.895 mm-1, Rint = 0.0921, R = 0.0649 and wR = 0.1325. Single-crystal X-ray structure analysis indicates that the title compound consists of a polyanion [HV8VV8IVO38（CI）]4- cage, two [Mn（en）3]2^2＋ cations, four and a half lattice waters and a half ethylenediamine. In addition, intermolecular O-H...N, O-H...O, N-H...O and C-H...O hydrogen bonds link the molecules together to form a three-dimensional structure.     

Modifications to the AOAC use-dilution test for quaternary ammonium compound-based disinfectants that significantly improve method reliability

The AOAC use-dilution test (UDT) for bactericidal disinfectant efficacy (Method 964.02) has often been criticized for its extreme variability in test results, particularly for quaternary ammonium compound (QAC)-based disinfectants against Pseudomonas aeruginosa. While efforts are under way to develop a new and better test method for hospital disinfectant products that is globally acceptable, U.S. manufacturers and formulators of QAC products must continue in the interim to measure their product performance against the current UDT method. Therefore, continued variability in the UDT places an unnecessary and unfair burden on U.S. QAC product manufacturers to ensure that their products perform against an, at best, unreliable test method. This article reports on evaluations that were conducted to attempt to identify key sources of UDT method variability and to find ways to mitigate their impact on test outcomes for the method. The results of testing across 4 laboratories, involving over 6015 carriers, determined that operator error was a key factor in test variability. This variability was found to be significantly minimized by the inclusion of a simple culture dilution step. The findings from this study suggest possible refinements to the current AOAC UDT method that would serve to improve the overall ruggedness and reliability of the method and to optimize recovery of cells from the carrier surface, thereby further improving the accuracy and reproducibility of counts and test outcomes until such time as a replacement method is implemented.     

Morphology of cold-drawn nylon 66

A nylon 66 composed of uniformly sized spherulites approximately 50 μ in diameter was examined before and after cold drawing by light and electron microscopy of thin sections and by low-angle x-ray diffraction. Spherulites retained their identity through drawing, but the spherulites elongated less than the bulk specimen indicating that relative motion of spherulities must have occurred. The observation of dilations (0.3 μ long) at interspherulitic boundaries support this contention. The thin-section electron micrographs indicated that the spherulites were composed of radiating lamellae approximately 95 A. thick. After drawing, the lamellae were preferentially oriented both parallel and perpendicular to the draw direction. Lamellae parallel to draw had thinned to approximately 70 A. While lamellae perpendicular to the draw had apparently thickened to 150 A. Three low-angle x-ray diffraction patterns yielded quantitative agreement with the electron-micrograph data. The pattern form the undrawn nylon was a diffuse ring corresponding to a 95 A. spacing. On the drawn specimen, with the beam parallel to draw, a ring corresponding to the 150 A. spacing was obtained, while with the beam perpendicular to draw two arcs were recorded at spacings of 70 and 150 A. The drawing was done at room temperature and proceeded by neck formation and propagation, yielding a 4:1 draw ratio.     

Synthetic Studies on the Ambiguine Family of Alkaloids: Construction of the ABCD Ring System

A racemic synthesis of the ABCD ring core of the ambiguines that preserves the tertiary alcohol has been accomplished in a convergent synthesis in 10 synthetic steps, in an overall yield of 46% from commercially available 4-bromoindole and m-methylanisole.