A study on a photochemical reaction in the system N,N-dimethylaniline-bromobenzene

The UV radiation absorbed by N,N-dimethylaniline dissolved in bromobenzene has been found to initiate a photochemical reaction. Resulting products were identified and a modified mechanism of the reaction has been suggested. To support the mechanism, quantum yields for the formation of some of the reaction products have also been determined.     

Anomalous intramolecular C-H insertion reactions of rhodium carbenoids: factors influencing the reaction course and mechanistic implications

The intramolecular insertion of rhodium carbenoids into the alpha-C-H bonds of allylic ethers to give 3(2H)-furanones has been explored. Cyclopropanation is favored irrespective of the complex used for carbenoid generation or the substitution pattern of the allylic ether, unless a substituent is placed on the tether connecting the ether to the alpha-diazo ketone. Unusual acetal products resulting from an anomalous C-H insertion process are obtained in addition to the expected 3(2H)-furanones formed by conventional carbenoid C-H insertion. These acetals are the favored C-H insertion products in certain circumstances and particularly in cases where carbenoid generation is effected using an electron-deficient rhodium complex. Experiments with simple deuterium labeled substrates reveal that anomalous C-H insertion products arise by a mechanism that is distinct from that leading to the formation of conventional C-H insertion products. The formation of acetal products and the outcome of reactions performed using deuterium-labeled substrates suggest that a mechanism involving hydride migration to the rhodium center of the carbenoid is operative.     

Thermal decomposition of cyclo-linear methylsiloxane polymers

The pyrolysis products from two cyclo-linear methylsiloxane polymers have been analysed, and formation of the important products interpreted in terms of a simple decomposition mechanism. This mechanism is very similar to that of the polydimethylsiloxane degradation; thus cyclic oligomers are formed from the linear segments, and polycyclic compounds from the cyclic segments of the cyclolinear methylsiloxane polymers.     

Application of analytical pyrolysis for wood fire protection control

The effect of two flame-retardant compositions (A-76% potassium carbonate, B-67% sulphate ammonium) on the process of thermal degradation of wood and the composition of volatile products of pyrolysis has been investigated by the thermogravimetry and analytical pyrolysis methods. It has been shown that the effect of flame retardants manifests itself in the low-temperature region with the formation of more thermally stable intermediate carbonized products. Upon pyrolysis of wood under the action of the composition A, the mechanism of degradation of the lignin component changes, which manifests itself in a more than two-fold increase in the guaiacol and vinylguaiacol contents in the composition of volatile products and the inhibition of the formation of carbohydrates destruction products. It has been found that the composition B has a catalytic action mainly on the process of thermal depolymerization of cellulose, favouring the increase in the formation of levoglucosan and practically does not change the yield of lignin degradation products.     

The mechanism of cleavage of 3-phenylallyl-silicon and -tin bonds by methanolic sodium methoxide

The distribution of deuterium in the hydroformylation products of ω-deuterated α-olefins is consistent with a reaction mechanism involving initial formation of an olefinic catalyst π-complex. The role of the intermediate complexes in the formation of the products in the hydroformylation of but-1-ene-4-d₃ has been evaluated.     

Etude de la reaction de lactonisation de l'acide ethylenedioxy-1,1 methyl-2 oxo-3 cyclopentane-2- propionique

The lactonisation of ethylene 1,1-dioxy 2-methyl 3-oxo cyclopentane-2 propionic acid has been affected by a new method whose mechanism is discussed. The formation of a β-diketone and other products by isomerisation of the enol lactone has been avoided. The enol lactone is an important intermediate in the total synthesis of steroids and has been prepared with a good yield by the new method.     

Influence of structural factors on degradation product formation: Primary pyrolysis products of poly(acyl sulfides) investigated by direct pyrolysis mass spectrometry

Thermal degradation of two poly(acyl sulfide) polymers, poly(adipoyl sulfide) (PADS) and poly(terephthaloyl sulfide) (PTS) was investigated by direct pyrolysis mass spectrometry (DPMS). The structures of pyrolysis products detected in the DPMS analysis of both PADS and PTS indicate that the thermal degradation takes place mainly through a loss of carbon monoxide and carbonyl oxysulfide leading to the formation of cyclics. In the case of PADS, linear products with thioacid end groups were formed through hydrogen transfer reactions. In the case of PTS, almost equal proportions of linear products with phenyl end groups and cyclic products were formed. The mechanism of formation of degradation products has also been addressed.     

Molecular beam studies of the F atom reaction with propyne: site specific reactivity

The dynamics of the F atom reaction with propyne (CH(3)CCH) has been investigated using a universal crossed molecular beam apparatus. Two reaction channels have been clearly observed: H+C(3)H(3)F and HF+C(3)H(3). The substitution of F for H occurs mainly via a complex formation mechanism, producing reaction products with some contribution from a direct reaction mechanism. The HF product, however, appears to be dominantly forward scattered relative to the F atom beam direction, suggesting that the HF formation occurs via a direct abstraction mechanism. Branching ratios for the two observed reaction channels are also determined. The H formation channel is found to be the major reaction pathway, while the HF formation channel is also significant. From the measurements of DF versus HF products from the F atom reaction with deuterated propyne, the H atom picked up by the F atom in the reaction with normal propyne seems to come mostly from the CH(3) group. In addition, the H atom produced in the H atom formation channel appears to be mostly from the CH(3) group with some contribution from the CCH group.     

等离子体反应合成全卤代

用聚四氟乙烯电弧蒸发和氯仿蒸气辉光放电方法合成了一系列全卤代芳香化合物,分离和表征了其中的全氟代芘(C₁₆F₁₀)和全氯代芘(C₁₆Cl₁₀),讨论了等离子体反应特征和产物形成机理。研究表明：等离子反应产物的形成不受起始物种、结构、形态和反应介质、放电方式的显着影响,而是形成了一系列结构相似的同系物.     

Diterpene chemistry : Transformations of 8(17), 14-labdadien-13-ol—Part 2

Aqueous permanganate oxidation of 8(17)-labden-13-ol gave two novel oxidation products by functionalisation of an unactivated carbon atom. The structures have been confirmed by degradative studies and a mechanism to account for their formation is proposed.     

Controllable assembly of WO3 nanorods/nanowires into hierarchical nanostructures

The controlled synthesis of two novel h-WO3 hierarchical structures made of nanorods/nanowires has been successfully realized in a large scale via a simple hydrothermal method. It is demonstrated that the morphology of the final products is significantly influenced by adding different sulfates. The urchinlike and ribbonlike structures of WO3 can be selectively prepared by adding Rb2SO4 and K2SO4, respectively. The morphology evolvement and the growth mechanism were studied carefully. The sulfate-induced oriented attachment growth mechanism has been proposed for the possible formation mechanism of the ribbonlike sample. For urchinlike products, two growing stages are believed to be involved in the growth process. The current understanding of the growth mechanism of these nanostructures may be potentially applied for designing other oriented or hierarchical nanostructures based on 1D nanoscale building blocks through the direct solution-growth.     

Cadmium photosensitized decomposition of ethane

The photosensitized decomposition of ethane has been carried out at temperatures of 533, 553, and 573°K and over a pressure range from 3 to 40 Torr. The principal products were hydrogen, ethylene, butane and methane. A mechanism to account for the pressure and temperature dependence of the products is invoked which involves production of ethylene by unimolecular decomposition of ethyl radicals as well as by disproportionation of ethyl radicals. The formation of butane can be accounted for in terms of pressure dependent free radical recombination Hydrogen is assumed to arise by H atom abstraction from reactant. Methane formation is shown to involve secondary processes. These results agree as to major products but differ in minor products from earlier work on the Cd photosensitized decomposition of ethane and also from the high temperature mercury photosensitized decomposition.     

Pinic and pinonic acid formation in the reaction of ozone with alpha-pinene

The mechanism of formation of key compounds in atmospheric secondary aerosol (SOA) has been investigated by studying the products of the ozonolysis of an enal derived from alpha-pinene using gas chromatography coupled to mass spectrometry.     

Kinetics of oxidation of some disaccharides in ammoniacal medium

Kinetics of oxidation of lactose, maltose, cellobiose and melibiose has been studied by hexacyanoferrate(III) in the presence of ammonia. A general mechanism involving the formation of intermediate enodiol anion has been suggested. The effects of dielectric constant and salts have been studied in detail. The oxidation products have been characterised by descending paper chromatography. Compensation effects have been observed.     

Synthesis, mechanism of formation, and molecular orbital calculations of arylamidoximes

Abstract  

A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well as arylamides, from arylnitriles and hydroxylamine is suggested. Quantum mechanical calculations have been carried out to support this mechanism. The enthalpy of formation in conjunction with atomic charges of the reactants and intermediates helped to understand more about the generation of the products.     

Organic acid formation in the gas-phase ozonolysis of alpha-pinene

The mechanism of formation of pinonic and norpinonic acids from alpha-pinene ozonolysis has been investigated by studying the products of the ozonolysis of an enone derived from alpha-pinene using gas chromatography coupled to mass spectrometry.     

Craquage thermique de l'aniline 1-14C

Thermal cracking of aniline 1-¹⁴C at atmospheric pressure at 900°C and a contact time of 2.5 sec breakdown mechanisms of the formation of benzene with an elimination of nitrogen, and formation of heterocyclic compounds and condensation products has been studied. Most of the degradation compounds are produced by a mechanism similar to the primary mechanism for the degradation of phenol: elimination of HCN with formation of inactive C₅H₆. The formation of nitriles is not negligible.     

Comparison of stir bar sorptive extraction and membrane-assisted solvent extraction as enrichment techniques for the determination of pesticide and benzo[a]pyrene residues in Brazilian sugarcane juice

The biodegradation of the organophosphorus insecticide methyl parathion (MP) in aqueous environment by bacteria isolated from river sediment has been studied. Two species of bacteria which show strong MP degradation ability are identified as Shewanella and Vibrio parahaemolyticus. The biodegradation of MP proceeded rapidly with the formation of a series of intermediate products, which were analyzed using a combination of GC/MS and HPLC/ESI-TOFMS techniques. The major products tentatively identified include a series of reduced products of MP. Results demonstrate that the coupling of TOFMS to HPLC enhances further the capability of LC-MS in the identification of polar organic species in complex environmental samples. Degradation pathways leading to the formation of these products are proposed which involves first the reduction of nitro to amino group in MP, followed by combination with some intrinsic matters of bacteria. The mechanism and products from biodegradation are quite different from those of photocatalytic process for which the main intermediates included methyl paraoxon and 4-nitrophenol.     

γ-Radiolysis of isobutanol and nitrate in aqueous solution

Radiolysis of isobutanol-nitrate aqueous solutions has been investigated in both aerated and deoxygenated solutions. Nitrate acts as a good scavenger for hydrated electrons. It gets reduced to nitrite during radiolysis. Alcohol, on the other hand, is used as a hydroxyl radical scavenger leading to the formation of aldehyde as the stable product. Nitrite, aldehyde and hydrogen peroxide formed as the stable products have been estimated in each system. Concentrations of both species (nitrate and alcohol) in the aqueous solution affect the yield of the products significantly. The observed G-values of the different products are accounted for by the mechanism proposed.     

Cerium(IV) ammonium nitrate catalyzed green synthesis of 2-substituted 2,3-dihydro- quinazolin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones using a grinding technique

An efficient and facile method for the synthesis of 2-substituted 2,3-dihydro-quinazolin-4(1H)-ones from anthranilamide with aldehydes or ketones in the presence of cerium(IV) ammonium nitrate in water by a grinding technique has been developed. The structures of the new products were proved by IR, ¹H NMR, MS, and elemental analysis. A plausible mechanism for the formation of these products is proposed.