Kinetics and Mechanism of Oxidation of 1-Phenylsemicarbazide by Peroxydisulphate

Kinetics of oxidation of 1-phenylsemicarbazide (PSC) by peroxydisulphate ion (PDS) have been carried out where by the pseudo first order condition was verified at large excess of PDS concentration. The rate of the reaction was followed spectrophotometrically, The stoichiometry was found to be 1:1 where 1-phenylazoformamide is the oxidation product. The effect of acidity on the rate of oxidation was investigated for different temperatures. The parameters of activation ΔG*, ΔH* and ΔS* were computed for both hydrogen ion depedent and hydrogen ion independent reaction pathes. A free radical mechanism was proposed.     

One-pot near-ambient temperature syntheses of aryl(difluoroenol) derivatives from trifluoroethanol

Difluoroalkenylzinc reagents prepared from 1-(2'-methoxy-ethoxymethoxy)-2,2,2-trifluoroethane and 1-(N,N-diethylcarbamoyloxy)-2,2,2-trifluoroethane at ice bath temperatures underwent Negishi coupling with a range of aryl halides in a convenient one pot procedure. While significant differences between the enol acetal and carbamate reagents were revealed, the Negishi protocol compared very favourably with alternative coupling procedures in terms of overall yields from trifluoroethanol.     

Why is RCM Favoured Over Dimerisation? Predicting and Estimating Thermodynamic Effective Molarities by Solution Experiments and Electronic Structure Calculations

The thermodynamic effective molarities of a series of simple cycloalkenes, synthesised from α,ω-dienes by reaction with Grubbs' second generation precatalyst, have been evaluated. Effective molarities were measured from a series of small scale metathesis reactions and agreed well with empirical predictions derived from the number of rotors and the product ring strain. The use of electronic structure calculations (at the M06-L/6-311G** level of theory) was explored for predicting thermodynamic effective molarities in ring-closing metathesis. However, it was found that it was necessary to apply a correction to DFT-derived free energies to account for the entropic effects of solvation.     

Progress toward the total synthesis of frondosin C

A straightforward approach toward the total synthesis of frondosin C is described. This strategy involves a key one-pot, microwave-assisted 5-exo cyclization-Claisen rearrangement sequence that was used for the expedient assembly of the frondosic C scaffold. Subsequent manipulation of the tetracyclic core allowed the synthesis of an advanced intermediate bearing the characteristic diene moiety in the B ring. [reaction: see text]     

Eigenvalues and eigenfunctions of discontinuous Sturm--Liouville problems with eigenparameter-dependent boundary conditions

We extend some fundamental spectral properties of classic regular Sturm--Liouville problems to discontinuous boundary-value problems with eigenvalue-dependent boundary conditions. We suggest a new approach for investigation of such type discontinuous problems.     

Multi-component orbital interactions during oxyacyl radical addition reactions involving imines and electron-rich olefins

Ab initio and DFT calculations reveal that oxyacyl radicals add to imines and electron-rich olefins through simultaneous SOMO-pi*, SOMO-pi and pi*-HOMO interactions between the radical and the radicalophile. At the BHandHLYP/aug-cc-pVDZ level, energy barriers of 20.3 and 22.0 kJ mol(-1) are calculated for the attack of methoxycarbonyl radical at the carbon and nitrogen ends of methanimine, respectively. In comparison, barriers of 22.0 and 8.6 kJ mol(-1) are calculated at BHandHLYP/aug-cc-pVDZ for reaction of methoxycarbonyl radical at the 1- and 2-positions in aminoethylene, respectively. Natural bond orbital (NBO) analysis at the BHandHLYP/6-311G** level of theory reveals that SOMO-pi*, SOMO-pi and pi*-LP interactions are worth 111, 394 and 55 kJ mol(-1) respectively in the transition state (8) for reaction of oxyacyl radical at the nitrogen end of methanimine; similar interactions are observed for the chemistry involving aminoethylene. These multi-component interactions are responsible for the unusual motion vectors associated with the transition states involved in these reactions.     

Synthesis of seven-membered carbocyclic rings via a microwave-assisted tandem oxyanionic 5-exo dig cyclization-claisen rearrangement process

Appropriately substituted 1-alkenyl-4-pentyn-1-ol systems, readily prepared from simple starting materials, serve as useful precursors to a number of substituted cyclohept-4-enone derivatives via a microwave-assisted tandem oxyanionic 5-exo cyclization/Claisen rearrangement sequence. The reactions involving terminally substituted 4-pentyn-1-ols were found to be highly stereoselective, with the alpha and beta groups in the final product showing a strong preference for the trans orientation.     

〈331〉晶向ZnTe单晶的太赫兹辐射-探测性能理论研究

根据光整流效应辐射太赫兹理论,计算了〈331〉晶向ZnTe单晶的太赫兹辐射性能.通过与〈110〉、〈111〉晶向对比,当晶体方位角为0°或180°时,利用〈331〉晶向ZnTe单晶辐射太赫兹信号可以与〈111〉晶向相当,强于〈110〉晶向.利用电光取样原理,计算了〈331〉晶向ZnTe单晶的太赫兹探测性能,通过理论计算为〈331〉晶向ZnTe 晶体有效辐射太赫兹波提供理论依据.     

A green and simple method for the synthesis of 2,4,5-trisubstituted-1H-imidazole derivatives using acidic ionic liquid as an effective and recyclable catalyst under ultrasound

Research on Chemical Intermediates - In the current work, an acidic ionic liquid ([{(IMC)-4-OMBH}BIM][HSO4]3) has been utilized as an effective and recyclable catalyst for the synthesis of...