Simultaneous Paths Research Articles

Kinetics of the Ligand Substitution Reactions of Tetrahedral Complexes [Co(NN)(hmpa)2]2+(NN=2,2′-Bipyridine, 4,4′-Dimethyl-2,2′-bipyridine, or 1,10-Phenanthroline) in Hexamethylphosphoric Triamide, Nitrobenzene, Acetone, 1,2-Dichloroethane, and Nitromethane

Abstract The substitution reaction rates of hexamethylphosphoric triamide (HMPA) for NN (NN=2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), or 1,10-phenanthroline (phen)) on tetrahedral complexes [Co(NN)(hmpa)2]2+ were determined spectrophotometrically in pure HMPA or in nitrobenzene, acetone, 1,2-dichloroethane, and nitromethane at various concentrations of HMPA, for the purpose of clarifying the reaction mechanism and the effect of the bulkiness of HMPA. The ligand substitution reaction on bpy and dmbpy complexes proceeds simply via a dissociative mechanism in nitrobenzene. In inert solvents other than nitrobenzene, it proceeds in parallel via two simultaneous paths of both dissociative and associative mechanisms. In the case of the phen complex, the reaction proceeds only by a dissociative mechanism in pure HMPA and in all the inert solvents used. The activation enthalpies and the activation entropies of the dissociative mechanism of bpy and dmbpy complexes were (80–90) kJ mol−1 and approximately zero J K−1 mol−1, respectively, in all the solvents used. Those for the phen complex were (86–101) kJ mol−1 and (−16–+36) J K−1 mol−1, respectively, while those of the associative mechanism for bpy and dmbpy complexes in all the solvents used except nitrobenzene were (50–65) kJ mol−1 and large negative values, respectively. Whether the substitution proceeds by the dissociative mechanism or by the associative one, both the steric and the solvent effects appear seriously, because HMPA is a bulky ligand and had a large dipole moment.

A digital high-frequency multipath propagation simulator

A digital h.f. multipath propagation simulator is described which can be applied to communications receiver and modulation techniques evaluation and operator training. It can also be applied to a variety of applications in the high-frequency field where programmable and repeatable ionospheric conditions require simulation. Simultaneous communications paths are simulated, four of which exhibit independent delays, Doppler shifts, Rayleigh fade and phase variations and attenuation consistent with ionospheric reflection (skywave) paths.

Reactions of N-heteroaromatic bases with nitrous acid. Part 4. Kinetics of the diazotisation of 2- and 4-aminopyridine 1-oxide

The kinetics of the diazotisation of 2- and 4-aminopyridine 1 -oxide have been studied in 0.0025–5.0M-perchloric acid. The reaction is of the first order in both the amine and nitrous acid. The rate coefficient of the reaction increases with an increase in the concentration of perchloric acid and of sodium perchlorate. In perchloric acid solutions whose ionic strength is maintained constant by the addition of sodium perchlorate the rate constant for the reaction does not show a linear dependence on the h0 parameter for the medium, in contrast to the reported linear relationship between the rate coefficient for the diazotisation of 2- and of 4-aminopyridine and the h0 function. The results suggest that diazotisation of 2- and 4-aminopyridine 1 -oxide proceeds by two simultaneous reaction paths both of which contribute significantly to the overall reaction rate. The first involves attack of the nitrous acidium ion on the free amine whilst the second involves attack of the same nitrosating agent on the protonated amine. The amines react faster in the free than in the protonated form. The free and protonated forms of 4-aminopyridine 1 - oxide are diazotised at a greater rate than the corresponding forms of 2-aminopyridine 1-oxide.

Photointeraction on the Surface of Titanium Dioxide between Oxygen and Carbon Monoxide

In the range of 2100 to 3900 Å wavelength irradiation carbon monoxide is oxidized by oxygen into carbon dioxide at room temperature on the surface of titanium dioxide (anatase) non porous particles. Kinetic and isotopic exchange results show two simultaneous paths for this oxidation of CO, one requiring oxygen from the lattice of TiO2, the second involving adsorbed and dissociated oxygen.

ChemInform Abstract: A KINETIC STUDY OF THE LIGAND SUBSTITUTION REACTION OF TETRAMETHYLENEDIAMINETETRAACETATOCOBALTATE(II) WITH TRIMETHYLENEDIAMINETETRAACETATE

Chemischer InformationsdienstVolume 4, Issue 44 Organoelement Compounds ChemInform Abstract: A KINETIC STUDY OF THE LIGAND SUBSTITUTION REACTION OF TETRAMETHYLENEDIAMINETETRAACETATOCOBALTATE(II) WITH TRIMETHYLENEDIAMINETETRAACETATE HIROSHI OGINO, HIROSHI OGINOSearch for more papers by this authorTOSHIYUKI WATANABE, TOSHIYUKI WATANABESearch for more papers by this authorJONG-JAE CHUNG, JONG-JAE CHUNGSearch for more papers by this authorNOBUYUKI TANAKA, NOBUYUKI TANAKASearch for more papers by this author HIROSHI OGINO, HIROSHI OGINOSearch for more papers by this authorTOSHIYUKI WATANABE, TOSHIYUKI WATANABESearch for more papers by this authorJONG-JAE CHUNG, JONG-JAE CHUNGSearch for more papers by this authorNOBUYUKI TANAKA, NOBUYUKI TANAKASearch for more papers by this author First published: October 30, 1973 https://doi.org/10.1002/chin.197344419AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume4, Issue44October 30, 1973 RelatedInformation

A Signal Processing System for a Semiconductor Detector Ladder

The resolution of the NBS high resolution electron spectrometer has been improved recently by installing a new 48 channel detector array at its focal plane, in place of the original channel array that has been in use for some time. This has necessitated the design and construction of a new electronics system to accommodate the increased amount of information from the detectors. The new detector system digitally processes the signals from the detectors after amplification and discrimination. It is coupled on line to a computer which accumulates and manipulates the processed data. An effective and economical solution has been found for the construction of a large logic network for nuclear data accumulation. The functions provided are those normally found only in modular from; e.g. coincidence, with the necessary time resolution. Time differences for simultaneous signal paths have been restricted to ±1 ns maximun with a minimum pulse width of 5 ns for any pulse input. The entire system is dc coupled and the pulse pair resolution, measured during construction, is 10 ns.