Stopped-flow Fourier transform infrared spectroscopy of nitromethane oxidation by the diiron(IV) intermediate of methane monooxygenase

The hydroxylase component (MMOH) of soluble methane monooxygenase from Methylococcus capsulatus (Bath) was reduced to the diiron(II) form and then allowed to react with dioxygen to generate the diiron(IV) intermediate Q in the first phase of a double-mixing stopped-flow experiment. CD3NO2 was then introduced in the second phase of the experiment, which was carried out in D2O at 25 degrees C. The kinetics of the reaction of the substrate with Q were monitored by stopped-flow Fourier transform infrared spectroscopy, observing the disappearance of the asymmetric NO2 bending vibration at 1548 cm-1. The data were fit to a single-exponential function, which yielded a kobs of 0.45 +/- 0.07 s-1. This result is in quantitative agreement with a kobs of 0.39 +/- 0.01 s-1 obtained by observing the disappearance of Q by double-mixing stopped-flow optical spectroscopy at its absorption maximum of 420 nm. These results provide for the first time direct monitoring of the hydroxylation of a methane-derived substrate in the MMOH reaction pathway and demonstrate that Q decay occurs concomitantly with substrate consumption.     

Oxidation of coordinated olefins: the reactions of Cl2 with trichloro(ehtylene)platinate(II)

The oxidation of [PtCl₃(C₂H₄)]- by Cl₂ in aqueous solution, to yield CH₂ClCH₂OH and [PtCl₄]^2-, has been shown to proceed through the following sequence of steps: [PtCl₃(C₂H₄)] Cl₂Cl [PtCl₅(CH₂CH₂Cl)]^2-$\text{H}{}_2\text{O}\text{(HCl)}$ [PtCl₅(CH₂CH₂OH)]^2- → [PtCl₄^2- + CH₂ClCH₂OHEach of the steps and intermediates in this mechanistic sequence has been identified and characterized.     

Synthesis and characterization of new polyamides derived from di(4-cyanophenyl)isosorbide

New optically active polyamides were synthesized according to two ways: using a microwave-assisted polycondensation of an optically active isosorbide-derived diacylchloride with different aromatic diamines in NMP and using interfacial polymerization from an isosorbide-derived diamine with different diacylchlorides. The polymers are obtained with inherent viscosities in the range from 0.11 to 1.05 dL/g. The DSC and TGA measurements clearly demonstrate the high thermal stability of these polymers when considering the range of the melting points from 200 °C to 300 °C and the absence of decomposition till 350 °C.     

Préparation d'isoxazoles trisubstitués par réduction chimique et électrochimique d'α-acyl β-nitrostilbènes

Nitration of α-acylstilbenes with dinitrogen tetroxide leads to corresponding Z-α-acyl-β-nitrostilbenes. By chemical or electochemical reduction of these compounds, trisubstituted isoxazoles were prepared in good yields.     

Préparation de quelques 4-nitroisoxazoles à partir de pseudonitrosites de cétones éthyléniques du type chalcone

The Synthesis of some 4-Nitroisoxazoles from Pseudonitrosites of Chalcones The action of dinitrogen trioxide with α,β-unsaturated ketones of the chalcone type leads to pseudonitrosites (Table 1) which are cyclized to 4-nitro-3,5-diarylisoxazoles (Table 2).     

Locally compact groups acting on trees and propertyT

FollowingKazhdan, a separable locally compact groupG is said to have propertyT if the trivial representation is isolated in the dual space,, of equivalence classes of continuous irreducible unitary representations ofG. We generalize results ofMargulis—Tits by showing that groups which have propertyT can not be amalgams.Research supported by NSF.     

A diatropic ring current in a fluorofullerene trannulene

Ipsocentric current-density maps for a fluorofullerene derivative, C60F15H3, modelling the addition pattern of the experimentally characterised C60F15[CBr(CO2Et)2]3 which contains an [18]trans-annulene system, reveal a diamagnetic ring current dominated by the contribution of the four HOMO electrons, as in a classical (4n + 2) aromatic annulene.     

Action du chlorure de nitrosyle sur le trichloréthylène et sur le tétrachloréthylène

Nitrosyl chloride is only chlorinating in darkness and above 100°. In the sun light and at room temperature it reacts as a chlorinating, nitrosating, nitrating and oxidizing agent. With trichlorethylene in fact pentachlorethane 1,1,1,2-tetrachloro-2-nitrosoethane, 1,1,1,2-tetrachloro-2-nitroethane, dichloracetic acid and a compound of empirical formula C₄H₂Cl₅NO₂ are obtained. Tetrachloroethylene carried to hexachlorethane, pentachloronitrosoethane and tetrachloro-2-(pentachlorethyl)-1,2-oxazetidine. Introduced nitrosyl chloride provided nitrogen monoxide prouved by gaz chromatography. This monoxide reacted afterwards to give nitrogen which is the single nitrogenous gazeous compound. Carbondioxide is a minor component of the gaz.     

Millimeter-Wave Spectroscopy of Methylfuran Isomers: Local vs. Global Treatments of the Internal Rotation

Methylfurans are methylated aromatic heterocyclic volatile organic compounds and primary or secondary pollutants in the atmosphere due to their capability to form secondary organic aerosols in presence of atmospheric oxidants. There is therefore a significant interest to monitor these molecules in the gas phase. High resolution spectroscopic studies of methylated furan compounds are generally limited to pure rotational spectroscopy in the vibrational ground state. This lack of results might be explained by the difficulties arisen from the internal rotation of the methyl group inducing non-trivial patterns in the rotational spectra. In this study, we discuss the benefits to assign the mm-wave rotational-torsional spectra of methylfuran with the global approach of the BELGI-Cs code compared to local approaches such as XIAM and ERHAM. The global approach reproduces the observed rotational lines of 2-methylfuran and 3-methylfuran in the mm-wave region at the experimental accuracy for the ground vt=0 and the first torsional vt=1 states with a unique set of molecular parameters. In addition, the V3 and V6 parameters describing the internal rotation potential barrier may be determined with a high degree of accuracy with the global approach. Finally, a discussion with other heterocyclic compounds enables the study of the influence of the electronic environment on the hindered rotation of the methyl group.