The evaluation of frying oils with the p-Anisidine value

This study was conducted to examine the relationship of p-anisidine value with headspace volatiles, sensory evaluation, and polymers. Partially hydrogenated soybean frying oil was used to fry shoestring potatoes. The oil was evaluated by p-anisidine value, headspace volatile analysis, sensory evaluation, and polymer analysis. p-Anisidine value was found to be correlated with hexanal (r=0.81), heptanal (r=0.66), t-2-hexenal (r=0.81), t-2-heptenal (r=0.71), t-2-octenal (r=0.92), and t,t-2,4-decadienal (r=0.86) contents. p-Anisidine value was correlated with overall odor intensity (r=0.82) and correlated with fried food odor (r=0.53) and burnt odor (r=0.43). p-Anisidine value and polymers were also correlated (r=0.84).     

On the Twofold Heck Reaction of 4-vinylcyclohexene and p-dihalobenzenes

The palladium-catalyzed reaction of iodobenzene, p-haloiodobenzenes (p-C₆H₄IX′; X′F, Cl, Br, I) and p-dibromobenzene with 4-vinylcyclohexene (Heck arylation reaction of olefins) was investigated with Pd(OAc)₂/PR₃/Et₃N (R=phenyl, o-tolyl) as a classical catalyst system and with Pd(OAc)₂/KOAc/[BzEt₃N]Cl in DMF as a phase-transfer catalyst system, respectively. Iodobenzene reacts with 4-vinylcyclohexene to give (E)-2-(cyclohex-3-enyl) vinylbenzene ( 1 ) as main product. p-Haloiodobenzenes react with 4-vinylcyclohexene to give (E)-p-halo-2-(cyclohex-3-enyl) vinylbenzene ( 3 ), p-halo-1-(cyclohex-3-enyl) vinylbenzene ( 4 ) or (E,E)-p-bis[2-(cyclohex-3-enyl)vinyl]benzene ( 5 ) depending on the reaction conditions and the catalyst system used. The phase-transfer catalyst system is less reactive but more selective. A reaction temperature of 80°C is necessary for reaction with p-dibromobenzene. The investigations demonstrate the much higher reactivity of the exocyclic double bond of 4-vincylcyclohexene in comparison with the endocyclic one.     

The influence of mass transport on the deposit morphology and the current efficiency in pulse plating of copper

The morphology of copper deposits formed by pulse plating from an acid sulphate electrolyte is investigated. The steady and non-steady state conditions of mass transport are controlled by use of a rotating hemispherical electrode. Below the limiting pulse current density (i _pl), granular deposits are observed. Abovei _pl, regardless of the individual values of the pulse parameters, dendritic deposits are formed. Measured current efficiencies are compared with a theoretical model, which predicts a rapid decrease of the efficiency with the increasing ofi _p/i _pl fori _p/i _pl greater than one, wherei _p is the applied pulse current density. For a given set of pulse parameters, the measured current efficiency increases with the deposit thickness due to the increase of the effective surface area. This effect is particularly important for dendritic deposits.Nomenclature A apparent (effective) surface area (cm²) - A ₀ geometrical surface area (cm²) - D diffusion coefficient (cm²s^–1) - i current density (A cm^–2) - i _l limiting current density (A cm^–2) - i _p pulse current density (A cm^–2) - i _pl pulse limiting current density (A cm^–2) - i _m average current density in pulse plating (A cm^–2) - N _p dimensionless numberN _p=i _p/i _pl - N _m dimensionless numberN _m=i _m/i _l - t _p pulse time (s) - t_p relaxation time (s) - duty cycle, =t _p/(t _p+t_p) - (steady state) diffusion layer thickness (cm) - _p pulsating diffusion layer thickness (cm) - current efficiency - kinematic viscosity (cm²s^–1) - rotation rate (rad s^–1)     

Synthesis and properties of three kinds of phenylenevinylene copolymers with dialkoxyphenylene units

Two random copolymers, poly(p-phenylenevinylene-co-2,5-didodecyloxy-p-phenylenevinylene) and poly(2,5-dimethoxy-p-phenylenevinylene-co-2,5-didodecyloxy-p-phenylenevinylene), were synthesized via the chlorine precursor route followed by thermal elimination. One alternating copolymer, poly(p-phenylenevinylene-alt-2,5-didodecyloxy-p-phenylenevinylene), was prepared via the Heck coupling reaction. The effects of molar ratio of monomers on yield and composition of the precursor copolymers were studied. The two precursor copolymers and the alternating copolymer were characterized by gel permeation chromatography, differential scanning calorimetry, elemental analysis, and infrared spectroscopy. The UV-visible absorption spectra and photoluminescence spectra, as well as solubility and conductivity of these copolymers, were compared. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 937–946, 1998     

Indirect electrosynthesis ofp-methoxybenzaldehyde

High current efficiency and selectivity were obtained in the indirect electrochemical oxidation ofp-methoxytoluene top-methoxybenzaldehyde with Ce⁴⁺/Ce³⁺ as redox mediator system. Platinized titanium anodes can be used for oxidant regeneration. Selectivity ofp-methoxybenzaldehyde synthesis has been optimized up to 98% by Plackett-Burman and factorial design of experiments. The kinetics ofp-methoxytoluene oxidation by Ce⁴⁺ with CH₂Cl₂ as organic solvent has been found to be of mixed mass transfer and kinetic control.Nomenclature a _p specific interfacial area (cm^–1) - A _p interfacial area (cm²) - Ar aryl group - c concentration (moll^–1) - d diffusion layer thickness (cm) - E variable effect - E _A activation energy (kJ mol^–1) - j material flux (mol s^–1) - k mass transfer coefficient (cm s^–1) - n molar amount (mol) - n ⁰ starting molar amount (mol) - n ^rel relative molar amount - Q _r relative amount of charge - Q _th theoretical amount of charge - r reaction rate (moll^–1 s^–1) - r ⁰ initial reaction rate (moll^–1 s^–1) - S overall selectivity - T temperature (K) - X fractional conversion - v stoichiometric coefficient - ^e current efficiency - overall operational yield - dim dimerization product ofp-MT     

Reactor engineering models of complex electrochemical reaction schemes IV. Galvanostatic operation of series reactions with solvent decomposition

A mathematical analysis of series electrochemical reactions with solvent decomposition during galvanostatic batch operation is presented. Performance is compared to the equivalent system during potentiostatic operation by using the reduction of nitrotoluene to azoxytoluene as a representative model reaction scheme.Nomenclature C_j bulk concentration of species j - C_A0 initial concentration of A - C_Bmax minimum concentration of B - E electrode potential - F Faraday number - i _p partial current density of Stepp - i _T total current density - k _lj mass transfer coefficient of species j - k _f P electrochemical rate constant of Stepp - n _p number of electrons associated with Stepp - S electrode area - V batch reactor volume - constant describing potential dependency of reaction rate constant     

Disubstituted p-phenylene monomers. α-methyl- and α-phenyl-vinyl derivatives of benzene,biphenyl, p-terphenyl,and p,p′-diphenoxiybiphenyl

The high-yield syntheses of bis [p-(α-methylvinyl)] monomers of benzene, biphenyl, p-terphenyl, and 4,4′-diphenoxybiphenyl are reported. Also described are the syntheses of new bis[p-(α-phenylvinyl)] monomers of biphenyl, p-terphenyl, and 4,4′-diphenoxy-biphenyl. Infrared spectral data for the diolefinic monomers and their precursors are presented, together with brief details for the polymerization of the diolefins by means of free radical and Lewis acid catalysts.     

Esterification of ethenyl benzene and its derivatives with acetic acid in the presence of perchloric acid as a catalyst

The esterification process of ethenyl benzene and its derivative compounds (p-methyl, p-methoxy, p-chloro, m-methyl, m-nitro and m-chloro, respectively) was carried out with acetic acid and using perchloric acid as a catalyst. From the effects of the variables studied it could be concluded that: the temperature and the catalyst concentration influence positively over the olefin conversion, whereas the initial olefin concentration exert no effect over the same; and that the presence of perchloric salts exerts a different influence, depending on the temperature and on the catalyst concentration. It has been proven that the substituted radicals in the m- or p- positions exert an important influence over the conversion of the studied olefins, presenting growing reactivity in the following order: m-nitro ethenyl benzene, m-chloro ethenyl benzene, p-chloro ethenyl benzene, m-methyl ethenyl benzene, ethenyl benzene, p-methyl ethenyl benzene and p-methoxy ethenyl benzene. Finally, a kinetic and thermodynamic study has been done and the corresponding parameters have been calculated, with an adequate fitting.     

Synthesis, characterization, and oxygen permeability of homo- and copolymers from p-[tris(trimethylsilyl)silyl]-phenylacetylene

Summary Homopolymerization of p-[tris(trimethylsilyl)silyl]phenylacetylene [p(Me₃Si)₃SiPA] by Rh catalyst provided insoluble polymer. On the other hand, copolymerization of p(Me₃Si)₃SiPA with p-(trimethylsilyl)phenylacetylene (pMe₃SiPA) at 80:20, 50:50, and 20:80 feed ratios afforded high molecular weight copolymers (M _w > 1×10⁶), all of which were soluble in common solvents such as toluene and chloroform. The mole ratios of p(Me₃Si)₃SiPA to pMe₃SiPA unit in copolymers were close to those in the feeds. The oxygen permeability increased monotonously with increasing p(Me₃Si)₃SiPA content of copolymer in correspondence with fractional free volume; the value of the copolymer for the 80:20 feed ratio reached 770 barrers. Received: 30 August 2000/ Accepted: 6 September 2000     

Effect of Regiochemistry and Methylation on the Anticancer Activity of a Ferrocene-Containing Organometallic Nucleoside Analogue

Four new bis-substituted ferrocene derivatives containing either a hydroxyalkyl or methoxyalkyl group and either a thyminyl or methylthyminyl group have been synthesised and characterised by a range of spectroscopic and analytical techniques. They were included in a structure-activity-relationship (SAR) study probing anticancer activities in osteosarcoma (bone cancer) cell lines and were compared with a known lead compound, 1 -(S,R_p), a nucleoside analogue that is highly toxic to cancer cells. Biological studies using the MTT assay revealed that a regioisomer of ferronucleoside 1 -(S,R_p), which only differs from the lead compound in being substituted on two cyclopentadienyl rings rather than one, was over 20 times less cytotoxic. On the other hand, methylated derivatives of 1 -(S,R_p) showed comparable cytotoxicities to the lead compound. Overall these studies indicate that a mechanism of action for 1 -(S,R_p) cannot proceed through alcohol phosphorylation and that its geometry and size, rather than any particular functional group, are crucial factors in explaining its high anticancer activity.     

Pervaporation Separation of p-/o-Xylene Mixtures Using HTPB-Based Polyurethaneurea Membranes

Hydroxy terminated polybutadiene (HTPB)-based polyurethaneurea membranes with and without cross-linkage were synthesized and first used as membrane material to separate p-/o-xylene mixtures by pervaporation. Compared with HTPB-PU (without cross-linkage) membranes, HTPB-DVB-PU (cross-linked HTPB-PU with divinyl benzene) membranes demonstrated a lower degree of swelling in xylene isomer solutions and noticeable improved separation factor of p-/o-xylene. On the other hand, the amount of p-xylene adsorbed in HTPB-DVB-PU membranes increased significantly rather than that of o-xylene. While the separation factor of p-/o-xylene increased but the total flux decreased with increasing DVB content, which can be ascribed to the improved chemical structure and more homogeneous chain structures of the HTPB-DVB-PU membranes. The p-xylene normalized permeation rate and separation factor of p-/o-xylene of HTPB-DVB-PU membrane reached 2.70 kgµm/m²h and 2.23, respectively, at a feed concentration of 10 wt% p-xylene at 30°C.     

Inter-residual Hydrogen Bonding in Carbohydrates Unraveled by NMR Spectroscopy and Molecular Dynamics Simulations

Carbohydrates, also known as glycans in biological systems, are omnipresent in nature where they as glycoconjugates occur as oligo- and polysaccharides linked to lipids and proteins. Their three-dimensional structure is defined by two or three torsion angles at each glycosidic linkage. In addition, transglycosidic hydrogen bonding between sugar residues may be important. Herein we investigate the presence of these inter-residue interactions by NMR spectroscopy in D₂O/[D₆]DMSO (70:30) or D₂O and by molecular dynamics (MD) simulations with explicit water as solvent for disaccharides with structural elements α-d -Manp-(1→2)-d -Manp, β-d -GlcpNAc-(1→2)-d -Manp, and α-d -Glcp-(1→4)-β-d -Glcp, all of which have been suggested to exhibit inter-residue hydrogen bonding. For the disaccharide β-d -GlcpNAc-(1→2)-β-d -Manp-OMe, the large extent of O5′ ⋅⋅⋅ HO3 hydrogen bonding as seen from the MD simulation is implicitly supported by the ¹H NMR chemical shift and ³J_HO3,H3 value of the hydroxy proton. In the case of α-d -Glcp-(1→4)-β-d -Glcp-OMe, the existence of a transglycosidic hydrogen bond O2′⋅⋅⋅HO3 was proven by the presence of a cross-peak in ¹H,¹³C HSQC-TOCSY experiments as a result of direct TOCSY transfer between HO3 of the reducing end residue and H2′ (detected at C2′) of the terminal residue. The occurrence of inter-residue hydrogen bonding, albeit transient, is judged important for the stabilization of three-dimensional structures, which may be essential in maintaining a conformational state for carbohydrate–protein interactions of glycans to take place in biologically important environments.     

Preparation of polymers with pendant quinonoid groups and their photocrosslinking with visible light irradiation

Photosensitive polymers with pendant quinonoid groups were prepared by the reaction of p-(benzoquinon-2-ylthio) acetic acid (QTAA) or p-(p-benzoquinon-2-ylthio)benzoic acid (QTBA) with hydroxyethyl methacrylate-methyl methacrylate copolymer. The polymers showed a strong π-π^* absorption band at around 410 nm and were efficiently crosslinked by visible light irradiation. Somewhat higher photosensitivity of QTAA-bound polymer compared with that of QTBA-bound polymer suggested some contribution of intramolecular hydrogen abstraction of QTAA to the photocrosslinking.     

Estimation of optimum anode geometry in chlor-alkali membrane cells

In order to explore the dependence of cell voltage on electrode geometries, precious metal oxide anodes (DSA^®) with the following three kinds of geometries were constructed: an assembled strip with a parallel array (louvre type), a circularly perforated plate and a flattened mesh. Voltages in the membrane cell of a laboratory scale were measured with chlorine gas evolution in NaCl solution. The cell voltages exhibited a linear relation to a unit cell characteristic dimension as well as to the square of the per cent open area of the anode, as predicted from the theoretical analysis of the primary current distribution in the two-dimensional rectangular model cell. Therefore, small sizes of the iterative pattern unit reduced cell voltages. Slopes of the linear relation gave the increase in solution resistivity caused by the gas bubbles, indicating the presence of a bubble curtain around the anode.Nomenclature d ₁ distance between the anode and the membrane - d ₂ thickness of the membrane - j averaged current density, i.e. the current divided by (width of the anode)x(height of the anode) - o _p per cent open area defined by Equation 2 - p pitch of the unit region - p _cp pitch of the unit region for the circularly perforated anode - p _L pitch of the unit region for the louvered anode - p _LW,p _SW pitch of the unit region for the mesh anode (see Fig. 2c) - r radius of the circular open part - V cell voltage of the whole cell - V _rs residual voltage, i.e. the sum of the voltages such as overpotential due to electrode kineties both at the anode and the cathode, ohmic drop in the catholyte, membrane potential drop and ohmic drop within both electrodes - _bc apparent resistivity of the anolyte containing gas bubbles - ₂ resistivity of the membrane - arctan (p _SW/p _LW)     

Synthesis and properties of poly(diphenylacetylenes) having ether linkages

Summary Polymerization of 1-phenyl-2-(p-phenoxyphenyl)acetylene (p-PhODPA), 1-phenyl-2-(p-methoxyphenyl)acetylene, and 1-phenyl-2-(p-n-butoxyphenyl)acetylene was examined. These monomers polymerized with TaCl₅-n-Bu₄Sn to give methanol-insoluble polymers in over 60% yields. Poly(p-PhODPA) was a yellow solid completely soluble in toluene, CHCl₃, etc., and its weight-average molecular weight was about 1.0x10⁶ or higher. This polymer was thermally very stable (the onset temperature of weight loss in TGA in air was 420 °C). Its oxygen permeability coefficient (P o ₂) was 37 barrers (P o ₂/P n ₂ 2.2) and similar to that of natural rubber. In contrast, the other two polymers did not completely dissolve in any organic solvent, and their thermal stability was lower.     

Crystal structures and melting points of saturated triacylglycerols in the β-3 phase

A comprehensive packing analysis is presented of the crystal structures of a large number of saturated triacylglycerols in the β-3 phase. The triacylglycerolsp.q.r have been grouped into four classes:r=p,p+2,p+4 andp+6. The length of the middle chain,q, dictates whether a β-2 or β-3 packing occurs. The latter packing arrangement is adopted whenq differs at least 4 fromp orr. The model-building approach starts from the known molecular conformation of β-210.10.10 and the T_‖ subcell packing mode of the hydrocarbon chains. Purely geometrical model-building allows a preliminary assignment of crystal structures. Crystal lattice energy calculations using the atom-atom potential method support these tentative assignments and clarify some details regarding the stacking of layers. In common with the β-2 phase crystal structures, the structure of the terrace-like arrangement of the terminal methyl groups plays a crucial role. Triacylglycerols with chains 1 and 3 differing 2 or 4 carbon atoms have a common arrangement of the end-methyl groups (type β-3A). Those with a difference of 0 (i.e. symmetrical) or 6 carbon atoms have a different, less favorable methyl terrace (type β-3B). The available experimental evidence (x-ray powder diffraction, unit-cell data and melting points) is entirely compatible with these proposals.     

Epoxidation of ethylenic linkages by chromic acid IV. Oxidation of triaryl olefins by chromium trioxide

The oxidation of 1,1,2-triphenylbut-1-ene by chromium trioxide in acetic anhydride gives 1,2-epoxy-1,1,2-triphenylbutane with fission products and 1,1,2-triphenylacetylethylene. Cis- and trans-1-p-chlorophenyl-1,2-diphenylprop-1-ene yield crystalline epoxides in satisfactory yields under similar conditions. The epoxides are stable towards aqueous sulphuric acid. 1,1,2-Triphenylethylene, 1,1-di-(p-chlorophenyl)-2-phenylethylene and 1,1-di-(p-bromophenyl)-2-phenylethylene are similarly oxidised but the epoxides are hydrated to the glycols by the action of aqueous sulphuric acid. Chromic acid in aqueous sulphuric acid brings about oxidative fission of the double bond without any rearrangement.     

Relationships between Phenolic Acid Concentrations,Transpiration, Water Utilization,Leaf Area Expansion,and Uptake of Phenolic Acids: Nutrient Culture Studies

Phenolic acid treatments of cucumber seedlings (Cucumis sativus cv “Early Green Cluster”) inhibited transpiration, water utilization, leaf area, and absolute and relative rates of leaf expansion. The cinnamic acids, ferulic and p-coumaric acids, were two to five times more inhibitory than the benzoic acids, p-hydroxybenzoic acid and vanillic acid. When phenolic acid concentrations were maintained at inhibitory concentrations through multiple successive treatments, percent inhibition of water utilization remained relatively constant for a given concentration and phenolic acid, percent inhibition of leaf area initially increased and then leveled off to a constant percent, and percent inhibition of transpiration and rates of leaf area expansion declined over time. Subsequently, p-coumaric acid was chosen as the model compound for further study. When p-coumaric acid was inhibitory, percent inhibition of transpiration, water utilization, and rates of leaf area expansion of actively growing leaves rapidly declined (i.e., was lost) as p-coumaric acid concentrations surrounding roots decreased. Absolute and relative rates of leaf expansion, for example, declined approximately 12 and 14%, respectively, for every 0.1 mM decline in p-coumaric acid concentration. Uptake of p-coumaric acid by cucumber seedling roots was continuous over the 24- or 36-hr periods monitored, but was not consistently related to the initial p-coumaric acid treatment concentrations. However, declining p-coumaric acid concentrations monitored at 6- or 12-hr intervals over the 24- or 36-hr periods continued to be highly correlated to the initial p-coumaric acid treatment concentrations. A 25% depletion by 13-d-old cucumber seedlings took 8.5, 12, 19.5, 25, and 29.5 hr for 0.125-, 0.25-, 0.5-, 0.75-, and 1-mM treatments, respectively. Uptake during periods when phenolic acid concentrations and root uptake (depletion from solution) were related appeared to represent periods dominated by apoplastic movement into the intercellular spaces of roots. Uptake during periods without this relationship likely represented periods dominated by symplastic movement. The ability of cucumber seedlings to modify active phenolic acid concentrations surrounding their roots suggests that cucumber seedling can directly influence the magnitude of primary and secondary effects of phenolic acids through feedback regulation.     

Electroreduction of (1<Emphasis Type="Italic">S,2S</Emphasis>)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol derivatives. Behaviour of electrogenerated species and applications to organic synthesis

Hydroxylamines electrogenerated from (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol derivatives (derivatives of p-nitrophenylserinol) are unstable in methanol–acetate buffer and practically stable in acetonitrile–aqueous acetate buffer. This latter medium was used to carry out subsequent reactions in situ involving the triacetylated p-hydroxylaminophenylserinol and various reagents. An azoxy compound was the major product isolated after reaction with maleic or phthalic anhydrides. In contrast, a benzoxazine dione was normally obtained with phthaloyl dichloride and a N-sulphonylated hydroxylamine was produced with p-toluenesulphonyl chloride.     

Synthesis and Properties of Cross-Linked Poly(vinylene-arsine)

Summary Cross-linked poly(vinylene-arsine)s (4) were synthesized by a free-radical terpolymerization of phenylacetylene (2), hexaphenylcyclohexaarsine (l), and p- or m-diethynylbenzene (p- or m-3) at different compositions in the presence of a catalytic amount of AIBN. The number-average molecular weights of the resulting polymers were a few thousands estimated by gel permeation chromatography (GPC) analysis. By gas chromatography (GC) analysis p-3 was found to be more reactive during the polymerization than m-3 and the resulting cross-linked polymer (p-4) showed lower solubility than that of m-4. The cross-linked poly(vinylene-arsine)s showed higher glass transition temperature in the measurement of differential scanning calorimetry (DSC) and more red-shifted emission in chloroform solution than that of the linear poly(vinylene-arsine). These properties could be tuned by varying the monomer feed ratio.