Energetic and Entropic Changes in Volume Work and Chemical Reactions

In the present study, energetic and entropic changes are investigated on a comparative basis, as they occur in the volume changes of an ideal gas in the Carnot cycle and in the course of the chemical reaction in a lead-acid battery. Differences between reversible and irreversible processes have been worked out, in particular between reversibly exchanged entropy (∆eS) and irreversibly produced entropy (∆iS). In the partially irreversible case, ∆eS and ∆iS add up to the sum ∆S for the volume changes of a gas, and only this function has an exact differential. In a chemical reaction, however, ∆eS is independent on reversibility. It arises from the different intramolecular energy contents between products and reactants. Entropy production in a partially irreversible Carnot cycle is brought about through work-free expansions, whereas in the irreversible battery reaction entropy is produced via activated complexes, whereby a certain, variable fraction of the available chemical energy becomes transformed into electrical energy and the remaining fraction dissipated into heat. The irreversible reaction process via activated complexes has been explained phenomenologically. For a sufficiently high power output of coupled reactions, it is essential that the input energy is not completely reversibly transformed, but rather partially dissipated, because this can increase the process velocity and consequently its power output. A reduction of the counter potential is necessary for this purpose. This is not only important for man-made machines, but also for the viability of cells.

Study on synergistic leaching of potassium and phosphorus from potassium feldspar and solid waste phosphogypsum via coupling reactions

To achieve the resource utilization of solid waste phosphogypsum(PG)and tackle the problem of utilizing potassium feldspar(PF),a coupled synergistic process between PG and PF is proposed in this paper.The study investigates the features of P and F in PG,and explores the decomposition of PF using hydrofluoric acid(HF)in the sulfuric acid system for K leaching and leaching of P and F in PG.The impact factors such as sulfuric acid concentration,reaction temperature,reaction time,material ratio(PG/PF),liquid–solid ratio,PF particle size,and PF calcination temperature on the leaching of P and K is systematically investigated in this paper.The results show that under optimal conditions,the leaching rate of K and P reach more than 93%and 96%,respectively.Kinetics study using shrinking core model(SCM)indicates two significant stages with internal diffusion predominantly controlling the leaching of K.The apparent activation energies of these two stages are 11.92 kJ·mol^(-1)and 11.55 kJ·mol^(-1),respectively.

Extraction of hydrogen chloride by a coupled reaction-solvent extraction process

A coupled reaction-solvent extraction process was used to remove HC1 from a simulated distiller waste. The extraction performances of various extractants and diluents were compared and the apparent basicity ofN235 （a mixture of tertiary amines） in various diluents was determined. The best results were obtained using N235 and isoamyl alcohol as the extractant and diluent, respectively. The yield of HC1 from the coupled extraction was 75% with this extraction system. The mechanisms for the removal of HC1 in both the direct and coupled extractions were investigated. For the coupled extraction, the formation of an RaNHC1 ion-pair complex was involved in the HC1 removal. For the direct extraction, the mechanism involved the formation of hydrogen bonds at high concentrations of HC1.

Recent advances in paired electrolysis coupling CO_(2) reduction with alternative oxidation reactions

Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)holds great promise in green energy conversion and storage.However,for current CO_(2) electrolyzers that rely on the oxygen evolution reaction,a large portion of the input energy is"wasted"at the anode due to the high overpotential requirement and the recovery of low-value oxygen.To make efficient use of the electricity during electrolysis,coupling CO_(2)RR with anodic alternatives that have low energy demands and/or profitable returns with high-value products is then promising.Herein,we review the latest advances in paired systems for simultaneous CO_(2) reduction and anode valorization.We start with the cases integrating CO_(2)RR with concurrent alternative oxidation,such as inorganic oxidation using chloride,sulfide,ammonia and urea,and organic oxidation using alcohols,aldehydes and primary amines.The paired systems that couple CO_(2)RR with on-site oxidative upgrading of CO_(2)-reduced chemicals are also introduced.The coupling mechanism,electrochemical performance and economic viability of these co-electrolysis systems are discussed.Thereby,we then point out the mismatch issues between the cathodic and anodic reactions regrading catalyst ability,electrolyte solution and reactant supply that will challenge the applications of these paired electrolysis systems.Opportunities to address these issues are further proposed,providing some guidance for future research.

Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-(Naphthalen-1-yl)phenyl Core

Carbosilane dendrimers with p-bromophenyl core were synthesized by alternating Grignard and hydrosilylation reaction. And the α-naphthalenyl was connected to the core by the Suzuki coupling reaction. A new carbosilane dendrimer with big π-conjugated structure [4-（naphthalen-l-yl）phenyl core] was given. It shows Suzuki coupling reaction is an effective and powerful core-functionalization method and the satisfactory result can be obtained through prolonging the reaction time with the increase of the generation of dendrimer.

Cobalt Schiff base complexes: Synthesis characterization and catalytic application in Suzuki–Miyaura reaction

3-Methoxysalicylaldehyde was condensed with the amines 4-aminoacetophenone and 2-amino-5-bromopyridine to obtain Schiff base ligands, 1 and 2, which were coordinated to cobalt salts as complex 1 and complex 2, respectively. The synthesized ligands and complexes were characterized by spectroscopic(FT-IR,UV–Vis,~1H-NMR and mass spectrometry), thermal(TGA) and elemental analysis. The structures of the complexes were verified by evaluating their magnetic susceptibility and spectroscopic evidences. Synthesized complexes were studied for their catalytic activity in the Suzuki–Miyaura cross-coupling of aryl halides with phenylboronic acid. Optimized reaction yields 90% of the cyanobiphenyl for complex 1 and 91% for complex 2 with 0.1 mmol of catalyst loading thereby substantiating the C\\C coupling efficiency of the synthesized complexes, 1 and 2.

An Efficient System TiCl_4-Al for the Homocoupling Reaction of Aromatic Aldehydes

The reduction of TiCl4(THF)2 with Al in CH2Cl2 gave a green solution of [Ti2(μ-Cl)2Cl4· (THF)4] (1) which was found to promote the reductive homocoupling of aromatic aldehydes to yield symmetrical 1, 2-diols with high diasterepselectivities.

Well-dispersed Palladium Nanoparticles Catalysts Prepared by Wood Nanomaterials for Suzuki Coupling Reaction

Herein, well-dispersed Palladium(Pd) nanoparticles(NPs) with good catalytic activities were prepared using a wood nanomaterial(WNM) as a reductant and a supporting agent. Various factors that influenced the NP morphologies, including reaction time, temperature, and precursor concentration were studied. The as-prepared Pd NPs/WNM showed good catalytic performance for Suzuki coupling reactions.

An Efficient Palladium-catalyzed Coupling Reaction for the Preparation of Biaryls and Polyaryls

In the case of Pd(PPh3)4 as catalyst and toluene as reaction solvent, the desired biaryls and polyaryls were synthesized in excellent yield and on a large scale.

A facile approach to asymmetrical biaryls via coupling reaction of aryl halides with sodium tetraphenylborate catalyzed by MCM-41-supported sulfur palladium(0) complex

Various functionalized asymmetrical biaryls can be synthesized in high to excellent yields via coupling reaction of aryl iodides or bromides with NaBPh4 catalyzed by MCM-41-supported sulfur palladium（0） complex. This palladium complex can be easily recovered and reused many times without loss of activity.

Oxygen-vacancy-anchoring Ni_(x)O_(y) loading towards efficient hydrogen evolution via photo-thermal coupling reaction

Oxygen vacancy(Vo)is a significant component in defect engineering.The present work reports the anchoring effects of initial Vo for further loading modifications and the reducing capacity of photoinduced Vo for pure water splitting.Herein,we propose Ni-loaded Cu-doped TiO_(2)(NCT)materials by successive doping and loading.The continuously added Ni ions should accumulate around the Vos and gradually grow into complete nickel oxide crystals,achieving a higher average valence state of the Ni species.NiO crystals can be detected on a 0.5%NCT sample,while the structure of Ni_(2)O_(3) has been confirmed with a higher nickel mass ratio.Moreover,the introduction of nickel oxide effectively improves the photochemical and electrochemical performance by the interface charge separation,finally reaching an H2 yield of 30.6 pmol/g-cat on 0.5%NCT for Vo-based photo-thermal coupling reaction,which consists of Vo generation in photo and Vo consumption in thermal environment.In situ infrared spectroscopy further indicated that the presence of high valence state nickel oxide hindered the H2 formation but effectively promoted the conventional oxidizing reaction,with an H2 yield of 20.6 mmol/g-cat in a methanol-water reaction on the 2.0%NCT material.In summary,Vo controls the morphological structure of Ni loading and produces diverse effects for reactions with dissimilar mechanisms,which provides a novel way to design modifications for promoting various chemical reactions.

Studies on the Preparation of Bioactive Oligomerstilbene by Oxidative Coupling Reaction(Ⅰ)-Preparation of Shegansu B using Silver Oxide as Oxidant

篢he oxidative coupling reaction of isorhapontigenin using sliver oxide as oxidant afforded a major product, named shegansu B（2）， which was isolated from the roots of Belamcanda chinensis (L．)DC. Both the natural and synthetic Shegansu B have the same potent antagonism activities of leukotriene B4，D4 receptor．

Primary amine coupling on nanocarbon catalysts: Reaction mechanism and kinetics via fluorescence probe analysis

Non-metallic nanocarbon materials catalyzed coupling reactions of primary amines to produce imine is an efficient,green and sustainable synthetic route,which has a wide application prospect in fine chemicals or pharmaceutical molecules.In the present study,we show firstly the relatively high catalytic activity of graphene oxide in the reaction of oxidative coupling of benzylamine(OCB),which is even comparable with typical metal-based catalysts,indicating the great potential of nanocarbon materials in this reaction system.More importantly,a novel twophoton fluorescence probe molecule(N-propyl-4-hydrazinyl-1,8-naphthalimide,NA)with special chemical structure of hydrazine functionality was synthesized.The probe NA could selectively react with aldehyde or ketone compounds,leading to the photoluminescence enhancement via inhibition of photo induced electron transfer(PET)process.The synthesized NA was applied as probe in carbon catalyzed OCB system to predict the existence of reaction intermediate benzaldehyde(BA),indicating the reaction pathway of oxidation-deamination-condensation in nanocarbon catalyzed OCB process.The proposed luminescence-probe strategy for revealing the kinetics and mechanism may also shed light in other reaction systems concerning the intermediates or products of ketones or aldehydes.

Coupling reaction mechanism of 2-(2-bromo-4-fluorophenyl)-1-cyclohexen-1-yl trifluoromethane-sulfonate

The detailed mechanism of CuI-catalyzed C-O intramolecular coupling reaction of 2-(2-bromo-4-fluoro-phenyl)-1-cyclohexen-1-yl trifluoromethane–sulfonate was studied with the density functional theory(DFT). The geometries of the reactants,transition states, intermediates and products were optimized at the B3LYP/6-31+G* level. Meanwhile, the single point energy of species involved in gas and solvent at B3LYP/6-311+G* level was individually investigated. Polarizable continuum models(PCM)were applied to the dioxane and water solutions at the same level, respectively. Results show that the rate-limiting step, M3→TS3,does not change in different solutions. However, the activation energy in a dioxane solution is lower than that in water, which explains the previous experimental results. Compared with the non-catalyzed reaction process, the activation energy of the ratelimiting step is reduced by 56.53 kJ mol-1 in gas and 44.84 kJ mol 1in solvent, demonstrating a high catalytic efficiency of CuI.

Low-valent Titanium Induced Reductive Coupling Reaction of Aryl Sulfonyl Chlorides with α,β-Unsaturated Esters

The reductive coupling reactions of aryl sulfonyl chloride induced by (TiCl4-Zn) reagent affords diaryl disulfide. However, reaction of aryl sulfonyl chloride with α,β-unsaturated ester under the same condition affords β-arylsulfo ester.