An Efficient Strategy for the Synthesis of 1,6-Naphthyridine-2,5-dione Derivatives under Ultrasound Irradiation

A flexible and efficient three-component reaction has been established for the synthesis of bioactive 1,6-naphthyridine-2,5-diones by using low-cost and readily accessible aminopyridinones, aromatic aldehydes, and Meldrum’s acid as starting materials. The main advantage of this synthetic method is that the yields of the resulting 1,6-naphthyridine-2,5-dione derivatives under ultrasound irradiation in water with acetic acid as catalyst are higher than those from the classical-heating method. The probable reaction mechanism indicates that the process involves a Knoevenagel condensation, Michael addition, and cyclization sequence.

Effect of Co-precursor Maliec Anhydride on the Thermal Decomposition of Acetyl Ferrocene: A Reaction Kinetic Analysis

Background: Thermal decomposition of iron-bearing organometallic complex acetyl ferrocene, (C5H4COCH3)Fe(C5H5), leads to hematite (α-Fe2O3) nanoparticles. Presence of maliec anhydride, C4H2O3 as co-precursor during thermal decomposition modifies the size of the particles as well as the quantity of the reaction product significantly. Objective: Kinetic analysis of the solid-state thermal reaction of acetyl ferrocene in the presence of varying amount of co-precursor maliec anhydride under inert reaction atmosphere has been studied in order to understand the reaction mechanism involved behind the formation of hematite and the role of co-precursor in the reaction process. For this purpose, reaction kinetic analysis of three mixtures of acetyl ferrocene and maliec anhydride has been carried out. Methods: Thermogravimetry under non-isothermal protocol with multiple heating rates has been employed. The data are analyzed using model-free iso-conversional kinetic techniques to estimate the activation energy of reaction and reaction rate. The most-probable reaction mechanism has been identified by master plot method. The kinetic triplets (activation energy, reaction rate, most probable reaction mechanism function) have been employed to estimate the thermodynamic triplets (ΔS, ΔH and ΔG). Observations: Acetyl Ferrocene (AFc) undergoes thermal decomposition in a four-step process leaving certain residual mass whereas maliec anhydride (MA) undergoes complete mass loss owing to melting followed by evaporation. In contrast, the (AFc1-x-MAx) mixtures undergo thermal decomposition through a two-step process, and the decompositions are completed at much lower temperatures than that in AFc. The estimated activation energy and reaction rate values are found strongly dependent on the extent of conversion as well as on the extent of mixing. Introduction of MA in the solid reaction atmosphere of AFc in one hand reduces the activation energy required by AFc to undergo thermal decomposition and the reaction rate, while on the other hand varies the nature of reaction mechanism involved. Results: The range of reaction rate values estimated for the mixtures indicate that the activated complexes during Step-I of thermal decomposition may be treated as ‘loose’ complex whereas ‘tight’ complex for the Step-II. From the estimated entropy values, thermal process of (AFc1-x-MAx) mixture for Steps I and II may be interpreted as ‘‘slow’’ stage. Conclusion: Variation of Gibb’s free energy with the fraction of maliec anhydride in the mixtures for Step-I and II indicate that the thermal processes of changing the corresponding activated complexes are non-spontaneous at room temperature.

Skeletal Rearrangement in the Ritter Reaction of Turpentine: A Novel Synthesis of P-menthane Diamides

A novel skeletal rearrangement in the Ritter reaction was examined which conveniently generated p-menthane diamides from turpentine. A probable reaction mechanism was proposed based on employing thermodynamic analysis. All the products were purified and characterised by 1H NMR, IR, X-ray crystallography and ESI+-MS.

Gas-surface reactions of nitrate radicals with vinyl-terminated self-assembled monolayers

Interfacial reactions between gas-phase nitrate radicals, a key nighttime atmospheric oxidant, and a model unsaturated organic surface have been investigated to determine the reaction kinetics and probable reaction mechanism.

Thermal decomposition of a molecular material {N(n-C4H9)4[FeIIFeIII(C2O4)3]}∞ leading to ferrite: A reaction kinetics study

A multi-step thermal decomposition of a molecular precursor, {N(n-C4H9)4[FeIIFeIII(C2O4)3}? has been studied using non-isothermal thermogravimetry (TG) measurements in the temperature range 300 to ~800 K at multiple heating rates (5, 10 and 20 K min-1). The thermal decomposition of the oxalate-based complex proceeds stepwise through a series of intermediate reactions. Two different isoconversional methods, namely, improved iterative method and model-free method are employed to evaluate the kinetic parameters: activation energy and rate of reaction, and the most probable reaction mechanism of thermal decomposition is also determined. The different reaction pathways leading to different steps in the TG profile have also been explored which are supplemented by earlier experimental observations of the present authors.

Kinetic and Mechanistic Study of the Reduction of Chromium(VI) by Lactic Acid

The kinetics and mechanism of the reduction of chromium(VI) by lactic acid (Lac) in aqueous acidic medium was studied with spectrophotometry in a temperature range of 298.15 K~313.15 K. Under the conditions of the pseudo-first order , the observed rate constant increased with the increase in [Lac] and . There is no salt effect. Based on the experimental results, a probable reaction mechanism of oxidation was proposed. The rate equation derived from the mechanism could explain all the experimental phenomena. Activation parameters along with rate constant of the rate-determining step have been evaluated.

The Autocatalytic Reduction of Ferriin by Malonic Acid with Regard to the Ferroin-Catalyzed Belousov-Zhabotinsky Reaction

The reduction of ferriin ([Fe(phen)3]3+, phen = 1,10-phenanthroline) by malonic acid (MA) differs from the reduction of Ce(IV) or Mn(III) ions by MA in its autocatalytic character and in a pregnant influence of oxygen, which behaves obviously as a catalyst. The time dependence of the ferroin-ferriin redox potential at the last stage of this reaction has a sigmoidal shape, which indicates autocatalysis. Under anaerobic conditions, the inflection time is of the order of several tens of minutes, since autocatalysis cannot proceed unless a sufficient amount of oxygen is produced via oxidation of water (OH- ions) with Fe(IV) formed by the ferriin dismutation. Under aerobic conditions, the inflection time decreases to a value of a few seconds. The probable reaction mechanism is discussed in detail.

Photo-Induced Decomposition of 2-Chloroaniline in Aqueous Solution

A study was performed on the oxidizing degradation of 2-chloroaniline (used as a model pollutant in water) by photolysis (λ = 254 nm). The change of spectrum and substrate concentration of treated solutions was measured spectrophotometrically as well as by HPLC. The yields of the degradation products (chloride ions, ammonium ions, formaldehyde, etc.) were studied as a function of UV-dose. Their initial quantumyields (Qi) were determined by specific analysis. It was shown that the substrate photolysis in the presence of N2O is most efficient, followed by degradation in media saturated with pure oxygen and air. A probable reaction mechanism for the photo-induced degradation of 2-ClA is presented.

Degradation of chlorinated benzaldehydes in aqueous solutions by UV-irradiation

Photoinduced degradation of chlorinated benzaldehydes was investigated using UV light with λ = 253.7 nm in aerated aqueous solutions. Substrate degradation rate as expressed by first order reaction kinetics revealed rate constants, k;7.45×10−3min-1,3.90×10−3min-1and3.90×11−2min-1for 2- chlorobenzaldehyde, 3-chlorobenzaldehyde and 4-chlorobenzaldehyde respectively. The decomposition of the substrates was related to the formation of chloride and formaldehyde by homolytic cleavage processes. initial quantum yields and photochemical “GiPH-values” are reported for the degradation of the substrates. Based on the qualitative HPLC analysis, a probable reaction mechanism for the photoinduced degradation of chlorinated benzaldehydes is also presented.

Radiation Induced Br-Transfer from Ethylbromide to Triethylsilane

The radiolysis of deoxygenated triethylsilane (Et3SiH) was studied in the presence of various concentrations of ethylbromide (EtBr) as a function of the radiation dose. Chain reactions are leading to rather high yields of Br-containing final products, e. g. using 0.93 mol/dm3 EtBr we obtained: Gi(Et3SiBr) = 138, Gi(HBr) = 40, Gi(Br2) = 15 and Gi(Et3Si–SiEt3) = 6, in addition to small amounts of unidentified oligomers. Based on the knowledge from previous steady-state and pulse radiolysis studies of Et3SiH, a probable reaction mechanism is postulated to allow explanation of the present results.