Thermal decomposition products of a chlorinated aromatic polyamide

Products from the thermal decomposition of a chlorinated aromatic polyamide fabric are described for conditions of pyrolysis and flaming and nonflaming oxidative degradation. Volatile degradation products were identified by gas chromatography-mass spectrometry (GC-MS) and the condensible fraction, by infrared (IR) spectroscopy, high-pressure liquid chromatography (HPLC), and MS. Nonvolatile char was characterized by IR and elemental analysis. Twenty-one compounds were identified as volatile products from pyrolysis at 550°C; the condensible material contained ammonium chloride and at least 22 organic compounds. From volatile compounds produced in flaming oxidative degradation 21 compounds were identified, of which CO, CO₂, and H₂O were prominent. Nonflaming oxidative degradation at 400 and 550°C produced 11 and 21 volatile identifiable compounds, respectively, and results from experiments at the higher temperature compared favorably with results from the flaming experiments. By comparison of data from this work with those from unchlorinated analogs (described in an earlier article), it is concluded that the incorporation of chlorine into the polymeric structure lowers the temperature for the onset of thermal degradation and alters the type and concentration of thermolytic products. The major degradation products can be explained by a mechanism similar to that proposed for aromatic polyamides with the exception of the formation of substantial amounts of ammonium chloride. It is proposed that the latter is formed by an initial acid-catalyzed hydrolysis reaction which is followed by deammoniation or by an intermolecular process that involves an isoimide intermediate.     

Flow-injection determination of sugars with immobilized enzyme reactions and chemiluminescence detection

Glucose is determined by reaction with gluocose oxidase to produce hydrogen peroxide which is quantified via a chemiluminescence reaction with luminol. Sucrose, maltose, lactose and fructose are determined by enzymatic conversion to glucose (using invertase, amyloglucosidase, lactase. and glucose isomerase, respectively) and subsequent determination of the glucose, All enzymes are immobilized on controlled-pore glass and contained in flow-through reactors. For glucose, sucrose, and maltose the linear log-log working range 0.2 μM-1 mM, with a detection limit of 0.1 μM; for lactose and fructose the linear working range is 3 μM-1 mM with a detection limit of 1 μM. Assay time is 2 min.     

Organometalliques portant une fonction eliminable en β : II. Competition en α et β eliminations a partir de β alkoxy et silyloxy α,α-dichlorocarbenoides

β-Alkoxy and -silyloxy α,α-dichlorocarbenoids, stable at low temperature (?100°C), undergo a rapid decomposition upon warming, either by α-elimination of ClLi or β-elimination of ROLi. β-Elimination is generally observed and leads to the formation of a dichloroalkene which reacts with excess of butyllithium (or lithium dialkylamide) to give the corresponding mono-substituted alkyne (or chloroalkyne) with good yields. α-Elimination is followed by the migration of a group from the alcoholic carbon to the carbenoid center; alkyl (or trimethylsilyl) α-chlorovinyl ethers are thus formed. The silyl derivatives are further cleaved by an excess of the metalating agent, to alkali α-chloroenolates of aldehydes or ketones. α-Elimination of LiCl is always observed when steric hindrance prevents any syn or anti conformation for the two groups (Ro - Li) involved in a β-elimination. Thus, when the bulky trimethylsilyloxy group leads to α-elimination, its replacement by a methoxy group affords the products of β-elimination.     

Isomeric hexyl‐ketohydroperoxides formed by reactions of hexoxy and hexylperoxy radicals in oxygen

Isomerization reactions of peroxy radicals during oxidation of long‐chain hydrocarbons yield hydroperoxides, and therefore play an important role in combustion and atmospheric chemistry, because of their action as branching agents in these chain reaction processes. Different formation mechanisms and structures are involved. Three isomeric hexyl‐ketohydroperoxides are formed via isomerization reactions in oxygen of either hexoxy RO or hexylperoxy RO₂ radicals. In the temperature range 373–473 K, 2‐hexoxy (C₆H₁₃O) radical in O₂/N₂ mixtures gives 2‐hexanone‐5‐hydroperoxide via two consecutive isomerizations. The second one is a H transfer from a HC(OH) group occurring via a seven‐membered ring intermediate: Its rate constant has been determined at 453 and 483 K, and the general expression can be written as Hexylperoxy C₆H₁₃O₂ radical, present in n‐hexane oxidation by oxygen/nitrogen mixtures in the temperature range 543–573 K, gives 2‐hexanone‐4‐hydroperoxide, 3‐hexanone‐5‐hydroperoxide, and 2‐hexanone‐5‐hydroperoxide. The first two are formed through an isomerization reaction via a six‐membered ring intermediate, and the last through an isomerization reaction via a seven‐membered ring intermediate. The ratio of the rate constant of the isomerization reactions of RO₂ radicals via a seven‐membered ring intermediate to that via a six‐membered ring is found to be 0.795, and the rate constant expression via a seven‐membered ring intermediate is proposed: The role of these reactions in the formation of radicals in the troposphere is discussed. Other products arising in the reactional path, such as ketones, furans, and diketones, are identified. Identification of these ketohydroperoxides was made using gas chromatography/mass spectrometry with electron impact, and with NH₃ (or ND₃) chemical ionization. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 354–366, 2003     

Evaluation of the impacts of gamma radiolysis on an ALSEP process solvent

Journal of Radioanalytical and Nuclear Chemistry - Separating the minor actinide elements (americium and curium) from the fission product lanthanides is an important step in closing the nuclear...     

Linear viscoelastic behavior of perfluorooctyl sulfonate micelles: effects of counter-ions

Linear viscoelastic behavior was investigated for aqueous solutions of perfluorooctyl sulfonate (C₈F₁₇SO⁻ ₃; abbreviated as FOS) micelles having a mixture of tetraethylammonium (N⁺(C₂H₅)₄; TEA) and lithium (Li⁺) ions as the counter-ions. The solutions had the same FOS concentration (0.1 mol l⁻¹) and various Li⁺ fractions in the counter-ions, φ_Li = 0−0.6, and the FOS micelles in these solutions formed threads which further organized into dendritic networks. At T ≤ 15 °C, the terminal relaxation time τ and the viscosity η, governed by thermal scission of the networks, increased with increasing φ_Li up to 0.55. A further increase of φ_Li resulted in decreases of τ and η and in broadening of the relaxation mode distribution. These rheological changes are discussed in relation to the role of TEA ions in thermal scission: Previous NMR studies revealed that only a fraction of TEA ions were tightly bound to the FOS micellar surfaces and these bound ions stabilized the thread/network structures. The concentration of non-bound TEA ions, C_TEA ^*, decreased and finally vanished on increasing φ_Li up to φ_Li ^* ≅ 0.6, and the concentration of the bound TEA ions significantly decreased on a further increase of φ_Li. The non-bound TEA ions appeared to catalyze the thermal scission of the FOS threads, and the observed increases of τ and η for φ_Li < 0.55 were attributed to the decrease of C_TEA ^*. On the other hand, the decreases of τ and η as well as the broadening of the mode distribution, found for φ_Li > 0.55 (where C_TEA ^* ≅ 0), were related to destabilization of the FOS threads/networks due to a shortage of the bound TEA ions and to the existence of concentrated Li⁺ ions. Viscoelastic data of pure FOSTEA and FOSTEA/FOSLi/TEACl solutions lent support to these arguments for the role of TEA ions in the relaxation of FOSTEA/FOSLi solutions. Received: 12 October 1999/Accepted: 1 November 1999