Observations on the swelling characteristics of the zwitterionic hydrogel of poly(1-3-sulfopropyl)-2-vinyl-pyridinium-betaine hydrogel

Samples of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (PSPV) have been synthesized to high conversion by free radical polymerization in aqueous solution of the zwitterionic monomer SPV with several concentrations of the crosslinker N,N′-methylene-bis-acrylamide (MBA). The densities of the resultant xerogels increased regularly with the content of MBA. Hydrogels obtained by swelling them in water and aqueous KSCN solution were examined by gravimetric and dimensional analysis. The water contents increased with decreasing content of MBA, the value of 92.7 wt% at the lowest MBA content being higher than that for other zwitterionic hydrogels. Enhanced swelling occurred in 1 M aq. KSCN at each MBA content, the total swelling being 98.1 wt% at the lowest crosslinker content. Swelling increased with increasing temperature. An approximate procedure to formulating swelling equilibrium in term of the volume fraction of water in hydrogel, in conjunction with the van’t Hoff equation, yields a small positive value for the enthalpy of swelling. This is compared with values derived similarly for other hydrogels.     

Multiresidue screening of pesticides in foods using retention time locking, GC-AED, database search, and GC/MS identification

Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database search, and GC/MS can be a powerful tool for identifying pesticides in a complex matrix.     

Synthesis of a new bidentate ferrocenyl N-heterocyclic carbene ligand precursor and the palladium (II) complex trans-[PdCl2(CfcC)], where (CfcC) = 1,1′-di-tert-butyl-3,3′-(1,1′-dimethyleneferrocenyl)-diimidazol-2-ylidene

A new ferrocenyl-N-heterocyclic carbene ligand precursor 1,1′-bis[(1-tert-butylimidazolium)-3-methyl]ferrocene dichloride has been synthesised and structurally characterised. The imidazolium salt was readily deprotonated in situ with KN(SiMe₃)₂ and reacted with [PdCl₂ (cod)] to afford the structurally characterised palladium (II) complex trans-[PdCl₂(C^∧fc^∧C)], where (cod) = 1,5-cyclooctadiene and (C^∧fc^∧C) = 1,1′-di-tert-butyl-3,3′-(1,1′-dimethyleneferrocenyl)-diimidazol-2-ylidene.     

Phase-transfer catalysis-3: Acetylation of 2-acylcycloalkanones

With the exception of 2-formylcyclohexanone, which yields the E-exo-enol acetate, the phase-transfer catalysed acetylation of 2-acylcyclohexanones produces the 1-acetoxycyclohexene derivatives as the major products. The 1-acetoxy derivative is also obtained in good yield from the acetylation of 2-methoxycarbonylcyclopentanone but, generally, acetylation of 2-acylcyclopentanones yields the E-exo-enol acetates. 2-Acetylcyclopentanone, however, produces not only the E- and Z-exo-enol acetates, but also the endo-enol acetate, in a ratio of ca 2:2:1. The exo and endo-enol acetates were distinguished by ¹³CNMR spectroscopy and use of LIS reagents confirmed the configurational assignments of the exo-isomers     

EXCITED STATES OF DNA AND ITS COMPONENTS AT ROOM TEMPERATURE—III. SPECTRA, POLARISATION AND QUANTUM YIELDS OF EMISSIONS FROM ApA AND poly rA*

Abstract— Corrected normalised emission spectra from 300 to 480 nm and their polarisation are reported for neutral and poly rA at room temperature. Yields are 4 times (ApA) and 6 times (poly rA) greater than the monomer. Comparison of emission spectra and polarisation spectra demonstrates heterogeneity of emission and, following attempts at spectral synthesis, comparison with experimental reference spectra allows the observed total emission spectra to be resolved into four components assigned as I monomer-like emission, II excimer fluorescence, HI monomer phosphorescence, IV excimer phosphorescence; the polarisation of the excimer fluorescences of ApA and poly rA are deduced. The observations can be understood quantitatively using a simple stacking model with excimer emissions originating in the stacked components. Quantitative differences between ApA and poly rA are due to their different hypochromism and extent of stacking. Differences of polarisation are attributed to different stacking geometries, and the directional properties of the transition moment suggest that the excimer fluorescence is largely charge-resonance in nature.     

Chemistry of 6 -pyrido[4,3- ]carbazoles part II: synthetic approaches to 6 -9-methoxy-5, 11-dimethylpyrido[4,3- ] fluorenes

Synthetic approaches to 6 -9-methoxy-5, 11-dimethylpyrido[4,3- ] fluorene are described, thus 2-[1-(4-pyridyl)ethyl]6-methoxyindanone has been reacted with vinylmagnesium bromide to yield 2-[1-(4-pyridyl)ethyl]-6 methoxy-1-vinyl-1-indanol. However, on dehydration this compound rearranges to 2-[1-(4-pyridyl)ethyl]-3-ethylidene-5-methoxyindene rather than the required isomer 3-ethylidine-2-[1-(4-pyridyl)ethyl]-5-methoxyindane needed fro pericyclic ring-closure to the pyrido[4,3- ]fluorene system. Reaction of -2-[1-methyl-1-(4-pyridyl)methylene]-6-methoxyindanone with ethylene triphenylphosphorane similarly gives 6-methoxy-spiro-2-[1-(2,3-dimethyl-3-(4-pyridyl)-cyclopropyl) indanone rather than the desired indane.     

Acidic ent-kauranoids from the metabolism of ent-kaura-2,16-dien-19-ol in gibberella fujikuroi

Three acidic ent-kauranoid metabolites have been obtained as the methyl esters (7, 8, and 9) from incubation of the [17-¹⁴C]-labelled dienol (1) with Gibberella fujikuroi. Spectroscopic studies of the triol ester (7) and chemical degradation of B-ring cleaved products establish the assigned structure (7). The structures of the other two metabolite esters are indicated to be 8 and 9 from the spectroscopic data.     

C.I. Calculations on the lower transitions in the terphenyl and quaterphenyl di-valent ions

Energies and transition dipole moments for the lower electronic transitions in the terphenyl and quaterphenyl di-valent ions have been calculated starting from the Pople SCF MO's for the ground state ions. The configuration interaction included about one-hundred singly and doubly excited configurations. The results of the calculations for the lower allowed electronic transitions are in very satisfactory agreement with the experimental spectra.     

Evaluating Suppliers of Complex Systems: A Multiple Criteria Approach

Organizations are frequently required to make long-term strategic choices regarding the design and manufacture of innovative process equipment and systems which address future needs. An important consideration in such choices is the evaluation of the unique capabilities of available suppliers. Typically, such evaluations must be made relative to multiple attributes or criteria. This paper examines one such supplier evaluation process in the context of a major international manufacturer of telecommunication equipment. The ad hoc method used by the organization to evaluate the multiple factors involved is presented, and an alternative, structured approach to deal with the multiple factors is then discussed.