Extent-based kinetic identification using spectroscopic measurements and multivariate calibration

Extent-based kinetic identification is a kinetic modeling technique that uses concentration measurements to compute extents and identify reaction kinetics by the integral method of parameter estimation. This article considers the case where spectroscopic data are used together with a calibration model to predict concentrations. The calibration set is assumed to be constructed from reacting data that include pairs of concentration and spectral data. Alternatively, one can use the concentration- and spectral contributions of the reactions and mass transfers, which are obtained by pretreatment in reaction- and mass-transfer-variant form. The extent-based kinetic identification using concentrations predicted from spectroscopic data is illustrated through the simulation of both a homogeneous and a gas–liquid reaction system.     

A Simple Method for the Synthesis of Unsymmetrical Trisubstttuted Guanidines

A simple method for the synthesis of sweet tasting N, N′, N″-trisubstituted guanidines is described. The key intermediate, carbonimidoyl dichloride 6 was prepared using a known method. Reaction of 6 with cydooctylamine followed by the sodium salt of 5-aminomethyltetrazole or the sodium salt of glycine afforded the desired guanidine. When the carbonimidoyl dichloride was allowed to react with (S)-α-phenethylamine followed by the sodium salt of glycine, the guanidine sweetener 2 was obtained.     

Synthesis of Some Spirooxazolidinones

In this communication, we wish to report the synthesis of some new spiro-4-oxazolidinones. Treatment of the potassium salt of 2-methyl-cyclohexane-1,3-dione (1) with α-chloroacetanilides (2 a-c) gave 4-aryl-6-methyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 a-c); and with α-halopropionanilides (2 d,e), the corresponding 4-aryl-2,6-dimethyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 d, e) were obtained.     

A NOVEL SYNTHETIC APPROACH TO 4-SUBSTITUTED QUINAZOLINES

Abstract

A novel two-step synthetic method to prepare 4-(thienyl)quinazolines (8a and 8b) is described. The method is based on the simultaneous reductive cyclization of a nitro group β to the carbonyl group in ketones under Leuckart reaction conditions. The method has been found useful for the syntheses of the 4-substituted quinazolines.     

Self-complementary Tetracationic Cyclophanes Containing 4,4′-Bipyridinium and 2,5-Dimethoxy-1,4-xylyl Subunits

4,4′-Bipyridinium-based tetracationic cyclophanes containing a 2,5-dimethoxy-1,4-xylyl unit were synthesized by using either m-terphenyl building blocks or incorporating a 4-hydroxy benzyl spacer between the complementary subunits. The cyclophanes show weak intramolecular charge-transfer (CT) bands in the visible region and one of the cyclophanes formed a green-coloured CT complex with ferrocene with an association constant (K _a) of 6.3?M^?1. The electrochemical parameters obtained for the cyclophanes indicate that all the redox processes are reversible.     

Synthesis and Properties of Polyamides of 2,2′-[Isopropylidenebis-(p-phenyleneoxy)] diacetic Acid

A group of six semiaromatic polyamides of 2,2′-[isopropylidenebis-(p-phenyleneoxy)]diacetic acid (Bisacid A₂) were synthesized by low-temperature solution polycondensation techniques. Six different diamines were condensed independently with Bisacid A₂ chloride in a mixture of N-methylpyrrolidone (NMP and hexamethylhosphoramide (HMPA). The polymers were obtained in 82–95% yield and possessed inherent viscosities in the range from 0.32 to 0.63 dL/g. The polyamides were characterized by IR and 'H-NMR spectra. The molecular weight and molecular weight distribution of the polyamides were determined by gel-permeation chromatography. The thermal stability, thermal degradation kinetics, crystallinity, density, and solubility were also determined. A model diamide (MDA) was synthesized from aniline and Bisacid A₂ chloride to confirm the formation of polyamides from diamines.     

Combustion-synthesized sodium manganese (cobalt) oxides as cathodes for sodium ion batteries

We report on the electrochemical properties of layered manganese oxides, with and without cobalt substituents, as cathodes in sodium ion batteries. We fabricated sub-micrometre-sized particles of Na_0.7MnO_2?+?z and Na_0.7Co_0.11Mn_0.89O_2?+?z via combustion synthesis. X-ray diffraction revealed the same layered hexagonal P2-type bronze structure with high crystallinity for both materials. Potentiostatic and galvanostatic charge/discharge cycles in the range 1.5–3.8 V vs. Na | Na⁺ were performed to identify potential-dependent phase transitions, capacity, and capacity retention. After charging to 3.8 V, both materials had an initial discharge capacity of 138 mA?h?g^?1 at a rate of 0.3 C. For the 20th cycle, those values reduced to 75 and 92 mA?h?g^?1 for Co-free and Co-doped samples, respectively. Our findings indicate that earlier works probably underestimated the potential of (doped) P2-type Na_0.7MnO_2?+?z as cathode material for sodium ion batteries in terms of capacity and cycle stability. Apart from doping, a simple optimization parameter seems to be the particle size of the active material.     

Synthesis of novel fluorescent molecule and its polymeric form with aniline as fluorescent and supercapacitor electrode materials

In this study, a fluorescent material, 2‐naphthyl‐4‐amino benzoate, is synthesized by the esterification of 4‐aminobenzoic acid with 2‐naphthol. This molecule is used in the bulk polymerization of aniline, which results in the formation of poly(aniline‐2‐naphthyl‐4‐aminobenzoate). For comparison, polyaniline and also poly(aniline‐4‐aminobenzoic acid) salts are prepared via bulk polymerization. Formation and properties of these polymeric materials are evaluated by Fourier‐transform infrared (FT‐IR), ¹³C nuclear magnetic resonance, matrix‐assisted laser desorption ionization, UV‐Vis, Fluorescence, X‐ray diffraction (XRD), Field emission‐scanning electron microscopy (FE‐SEM), Differential scanning calorimetry (DSC), thermogravimetric analysis, electrical resistance and electrochemical techniques. P(ANI‐2NA4ABA) is obtained in nanofiber morphology in 106 wt% yield with respect to the amount of aniline used with comparable conductivity of conventional polyaniline salts. This polymer salt is stable up to 220°C and indicates melting at 146°C on heating and crystal formation at 128°C on cooling. This polymer shows higher wavelength fluorescence compared to the conventional polyaniline salts. This polymer is used as an electrode material without binder, which shows a specific capacitance of 360 F g^?1 at 0.25 A g^?1.     

A Titanium Metal–Organic Framework with Visible‐Light‐Responsive Photocatalytic Activity

The one‐step synthesis and characterization of a new and robust titanium‐based metal–organic framework, ACM‐1 , is reported. In this structure, which is based on infinite Ti?O chains and 4,4′,4′′,4′′′‐(pyrene‐1,3,6,8‐tetrayl) tetrabenzoic acid as a photosensitizer ligand, the combination of highly mobile photogenerated electrons and a strong hole localization at the organic linker results in large charge‐separation lifetimes. The suitable energies for band gap and conduction band minimum (CBM) offer great potential for a wide range of photocatalytic reactions, from hydrogen evolution to the selective oxidation of organic substrates.     

Conformational Change from a Twisted Figure‐Eight to an Open‐Extended Structure in Doubly Fused 36π Core‐Modified Octaphyrins Triggered by Protonation: Implication on Photodynamics and Aromaticity

Two examples of core‐modified 36π doubly fused octaphyrins that undergo a conformational change from a twisted figure‐eight to an open‐extended structure induced by protonation are reported. Syntheses of the two octaphyrins (in which Ar=mesityl or tolyl) were achieved by a simple acid‐catalyzed condensation of dipyrrane unit containing an electron‐rich, rigid dithienothiophene (DTT) core with pentafluorobenzaldehyde followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). The single‐crystal X‐ray structure of the octaphyrin (in which Ar=mesityl) shows a figure‐eight twisted conformation of the expanded porphyrin skeleton with two DTT moieties oriented in a staggered conformation with a π‐cloud distance of 3.7 Å. Spectroscopic and quantum mechanical calculations reveal that both octaphyrins conform to a [4n]π nonaromatic electronic structure. Protonation of the pyrrole nitrogen atoms of the octaphyrins results in dramatic structural change, which led to 1) a large redshift and sharpening of absorption bands in electronic absorption spectrum, 2) a large change in chemical shift of pyrrole β‐CH and ? NH protons in the ¹H NMR spectrum, 3) a small increase in singlet lifetimes, and 4) a moderate increase in two‐photon absorption cross‐section values. Furthermore, nucleus‐independent chemical shift (NICS) values calculated at various geometrical positions show positive values and anisotropy‐induced current density (AICD) plots indicate paratropic ring‐currents for the diprotonated form of the octaphyrin (in which Ar=tolyl); the single‐crystal X‐ray structure of the diprotonated form of the octaphyrin shows an extended structure in which one of the pyrrole ring of each dipyrrin subunit undergoes a 180 ° ring‐flip. Four trifluoroacetic acid (TFA) molecules are bound above and below the molecular plane defined by meso‐carbon atoms and are held by N? H ??? O, N? H ??? F, and C? H ??? F intermolecular hydrogen‐bonding interactions. The extended‐open structure upon protonation allows π‐delocalization and the electronic structure conforms to a [4n]π Hückel antiaromatic in the diprotonated state.