P. K. Gutch

Poly-Schiff bases. V. Synthesis and characterization of novel soluble fluorine-containing polyether azomethines

A new dialdehyde monomer, 4,4′-(hexafluoroisopropylidine) bis(p-phenoxy) benzaldehyde, was prepared; it led to a number of novel poly-Schiff bases in reactions with different diamines, such as 4,4′-diaminidiphenyl ether, 4,4′-(isopropylidine) bis(p-phenoxy) dianiline, 4,4′-(hexafluoroisopropylidine) bis(p-phenoxy) dianiline, and benzidine. The polymers were characterized with viscosity measurements, nitrogen analyses, and IR and 1H NMR spectroscopy. These poly-Schiff bases showed good thermal stability up to 491 °C for 10% weight loss in thermogravimetric analysis under air and high glass-transition temperatures up to 215 °C in differential scanning calorimetry. These polymers were soluble in a wide range of organic solvents, such as CHCl3, dimethylformamide (DMF), dimethyl sulfoxide, and 1-methyl-2-pyrrolidon (NMP), and were insoluble in toluene and acetone. Thin films of these polymers cast from DMF exhibited tensile strengths up to 38 MPa.

Poly-schiff bases—II. Synthesis and characterization of polyetherketoimines

Abstract Six new poly-Schiff bases have been synthesized by solution polycondensation of six different diamines with 4,4′-aryl bis-(oxy)-bis acetophenone. The synthesized polymers were characterized by viscosity measurement, elemental analyses, i.r., X-ray diffraction, and differential scanning calorimetry. The thermal stability of the polymers was evaluated by thermogravimetric and isothermal gravimetric analysis. The polymers cured at a high temperature by the opening of C(CH3)N linkages. The electrical conductivities of the virgin and iodinedoped polymers are as high as 10−11 – 10−16 and 10−9 − 10−6 S/cm, respectively, at 30 °C. Variation in the electrical conductivity (σ) with temperature followed the empirical relation σ = σ 0 e −E a RT .

Poly-Schiff bases - IV. Synthesis and characterization of poly (etherazomethine)s

Twelve new poly(etherazomethine)s with linear structures were prepared by a conventional literature procedure by reacting six different diamines with two different bisaldehydes containing ether linkages in the backbone. The resulting polymers were confirmed by infrared (IR) elemental analysis and viscosity measurements. The thermal stability of the polymers was evaluated by thermogravimetry (TG) and isothermal gravimetric (IG) analyses. These polymers are reasonably good thermally and thermo-oxidatively stable. A semicrystalline behavior was noticed for these polymers by X-ray powder diffraction and differential scanning calorimetry measurements.

Catalytic removal of carbon monoxide over carbon supported palladium catalyst.

Carbon supported palladium (Pd/C) catalyst was prepared by impregnation of palladium chloride using incipient wetness technique, which was followed by liquid phase reduction with formaldehyde. Thereafter, Pd/C catalyst was characterized using X-ray diffractometery, scanning electron microscopy, atomic absorption spectroscopy, thermo gravimetry, differential scanning calorimetry and surface characterization techniques. Catalytic removal of carbon monoxide (CO) over Pd/C catalyst was studied under dynamic conditions. Pd/C catalyst was found to be continuously converting CO to CO(2) through the catalyzed reaction, i.e., CO+1/2O(2)→CO(2). Pd/C catalyst provided excellent protection against CO. Effects of palladium wt%, CO concentration, humidity, space velocity and reaction environment were also studied on the breakthrough behavior of CO.

Thermal analysis of interaction between 2-PAM chloride and various excipients in some binary mixtures by TGA and DSC

Pralidoxime chloride known as 2-PAM chloride is used as antidote for nerve agent’s poisoning. This study was undertaken to establish the compatibility of 2-PAM chloride with a number of commonly used excipients by using thermoanalytical technique viz., differential scanning calorimetry (DSC) and thermogravimetry/differential thermogravimetry (TG/DTG) used in pharmaceutical formulation. The TG and DSC both results demonstrated that polyvinyl alcohol, polyacrylamide, microcrestline cellulose, hydroxypropyl cellulose, cellulose acetate, ethyl cellulose found to be compatible with 2-PAM chloride and chosen for the preparation of antidote against chemical warfare agents.

Thermal decomposition studies of riot control agent ω-chloroacetophenone (CN) by pyrolysis-gas chromatography-mass spectrometry.

Pyrolysis-GC/MS system with on-line micro-furnace was used to make rapid evaluation of ω-chloroacetophenone (CN) decomposition under inert thermal atmospheres. The volatile products evolved during pyrolysis were analyzed by thermal gravimetric analysis (TGA) and Py-GC/MS to obtain specific thermogram and pyrogram. Thermal gravimetric analysis results showed that CN undergoes sublimation at 167°C prior to its decomposition at 229°C. Totally 45 degradation products were identified based on mass spectral library matching with the aid of correlation of the values of boiling point (bp) and retention time. A large number of mono-aromatics and polycyclic aromatic hydrocarbons were observed beyond 600°C. In addition to the aromatic hydrocarbons, oxygenated compounds were also observed during the pyrolysis process. The pyrolysis mechanism was proposed based on the determined pyrolysates and their relative abundance with temperature. The investigation results can provide significant information for understanding the thermal behavior of CN and evaluation of the potential influence of the pyrolysates to living being and the environment.

Oxidative decontamination of chemical warfare agent VX and its simulant using N,N-dichlorovaleramide

The optimized conditions have been reported for efficient, operationally simple and safe oxidative decontamination of chemical warfare agent O-ethyl-S-2-(N,N-diisopropylaminoethyl)methylphosphonothioate (VX) and its non-toxic simulant O,S-diethyl methylphosphonothioate (OSDEMP). A positive chlorine bearing reagent N,N-dichlorovaleramide (NCV) was tested successfully to effect decontamination of these compounds. These compounds were found to undergo instantaneous reaction with NCV in acetonitrile–water medium to form non-toxic products. The reaction was monitored by gas chromatography (GC) and the products were identified by gas chromatography coupled with mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. The advantages of using this reagent are its low cost of production, ease of synthesis from commercially available raw materials and good shelf life (of more than one year).

A derivatization strategy for the detection and identification of volatile trialkylphosphites using liquid chromatography-online solid phase extraction and offline nuclear magnetic resonance spectroscopy

We demonstrate herein the application of selective derivatization method that converts volatile and labile trialkylphosphites (TAPs) into virtually non-volatile, thermally stable, and UV absorbing derivatives. After simple sample preparation, purification/enrichment of the derivatives was achieved by using high performance liquid chromatography (HPLC) coupled to on-line post column solid phase extraction (SPE) system. These derivatives were subjected to (31)P{(1)H} NMR and 1D-selTOCSY experiments. Conclusive identification was achieved on the basis of their HPLC retention time and NMR spectral signatures ( [Formula: see text] , (n)JH-H, and (3)JP-H). This method was tested for the unambiguous identification of a mixture containing low concentrations (∼10μgmL(-1)) of trimethylphosphite (TMP), triethylphosphite (TEP), triisopropylphosphite (TIP), and tributylphosphite (TBP) along with a high concentration of irrelevant background chemicals. It offered a high dynamic range and good detection limit and recovery (>75%) without the need for special NMR probe heads or exotic NMR experiments.

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea (CC2) and suspending agents used for the preparation of decontamination formulation against chemical warfare agents

N,N′-dichloro-bis[2,4,6-trichlorophenyl]urea, known as CC2, is used as a reactive chemical decontaminant of mustard agents. The present study was undertaken to establish the compatibility of CC2 with a number of commonly used suspending agents, using thermoanalytical techniques viz., thermogravimetry (TG) and differential scanning calorimetry (DSC) with the support of Fourier transform infrared spectroscopy (FTIR). The results demonstrated the applicability of TG and DSC as a fast screening tool for analysing the compatibility of drug with excipients at the early stages of a preformulation process. Methylcellulose, hydroxypropylcellulose, and betaine were found to be compatible with CC2.

Studies on thermal degradation of benzylidene malononitriles

Thermal decomposition studies have been carried out using flash vacuum thermolysis (FVT) to find out the decomposition temperature for benzylidene malononitriles (BMNs) including 2-chlorobenzylidene malononitrile (cs), a widely used riot control agent. The FVT studies have been carried out in a specially designed all glass assembly at various temperatures ranging from 300 to 600°C. A number of rearranged products along with hydrogen cyanide were obtained as major decomposition products. The products were analysed and the structures were confirmed by GC/MS. the thermal behaviour of BMNs has also been investigated by TG under nitrogen atmosphere. These studies show that the pyrotechnic mixture for tear gas munitions should not have burst temperature above 300°C.