Preliminary Kinetic Investigations Research Articles

β-Aminomethylation of N-aryl- and N-azaheteroaryl-substituted methyl 2,5-dimethylpyrrole-3-carboxylates. Kinetic effect of the N-pyrrole substituent

Preliminary kinetic investigations 1,2 on substituted N-azaheteroaryl-substituted 2,5- dimethylpyrroles, showed that the relative reactivities of the pyrroles investigated are dependent on the nature of the N-substituent. In order to quantitatively study this influence, we synthesized methyl 2,5-dimethylpyrrole-3-carboxylates, containing as N-substituents a phenyl 9, a 2-pyridyl 10 and a 3-pyridyl 11 group; the β-methoxycarbonyl group was introduced in order to render the pyrrolic substrates amenable to the kinetic measurements. The obtained results support one of the proposed hypotheses.

Ethanol steam reforming in a molten carbonate fuel cell. A preliminary kinetic investigation

The decomposition of ethanol to CO x and H 2 was investigated under a wide range of operating conditions. High pressure reduces H 2, CO and CO 2 production, while high temperature produces the opposite effect. At T < 600 K the reaction also produces oxygenated compounds (acetaldehyde, ethyl acetate, acetic acid etc.) and H 2 yield is reduced. To extrapolate the kinetic findings obtained in the microreader at atmospheric pressure to ideal high pressure equipment, a mathematical model has been used. The simulation shows the feasibility of the process at temperatures between 800 and 1000 K, and pressures up to 100 bar. The use of a CuO/ZnO/Al 2O 3 catalyst exhibits good activity, and more expensive catalysts are unnecessary.

Preliminary kinetic investigation on syndiotactic polymerization of styrene

Polymerisation en presence de Ti(OC 4 H 9 ) 4 -methylalumoxane. La distribution de la masse moleculaire est bimodale

Oxygen-17 nuclear magnetic resonance spectroscopic studies of aqueous alkaline silicate solutions

High-field (11.75 T) oxygen-17 n.m.r. spectra have been obtained for a variety of aqueous silicate solutions isotopically enriched in the oxygen-17 nuclide. Oxygen-17 n.m.r. linewidths of the silicate anions are broad (Δv½ca. 3 to 20 p.p.m.) and the chemical shift range is relatively small (about 50 p.p.m.), often resulting in considerable spectral overlaps. Assignment of the observed resonances to known silicate structures is nevertheless possible in some cases by using suitable ‘model’ solutions containing silicate structures which have been previously characterized by 29Si n.m.r. spectroscopy and by making use of spectral simulations. In this manner, two overlapping spectral regions may be distinguished: a 35–55 p.p.m. range (from water) typical of non-bridging, or ‘terminal’ oxygen groups (Si–O– or Si–O–H, or both), and a 45–85 p.p.m. range, assigned to bridging groups (Si–O–Si). Contrary to recent Raman spectroscopic studies, 17O n.m.r. spectroscopy shows no evidence for any silicate species other than the monomeric silicate anion in very dilute solution (0.01 mol dm–3 in SiO2). Preliminary kinetic investigations indicate that in tetramethylammonium silicate solutions very different bulk water exchange rates exist for the two types of oxygen site present, with that for the non-bridging oxygen being much greater than that of the bridging oxygen. Concentrated alkali-metal silicate solutions yield complex 17O n.m.r. spectra with many overlapping signals.

Kinetics of nucleophilic attack on co-ordinated organic moieties. Part 8. Addition of NN-dimethylaniline to the tricarbonyl(dienyl)-iron, -ruthenium, and -osmium cations and related complexes

The complexes [M(C6H7)(CO)3][BF4](1; M = Fe, Ru, or Os) have been shown to act as electrophiles towards NN-dimethylaniline (RH) according to equation (I). A similar reaction occurs with [Cr(C6H7)(CO)3][BF4]. For [M(C6H7)(CO)3][BF4]+ RH →[M(C6H7R)(CO)3]+ HBF4(I)(1; M = Fe) and [Fe(C6H6OMe-2)(CO)3][BF4] the rate law, Rate =k[complex][RH] is observed. Preliminary kinetic investigations of the related reactions with (1; M = Ru or Os) provide the first quantitative comparison of the reactivity of cyclohexadienyl rings when co-ordinated to each of the iron triad metals, namely Fe > Os > Ru (41 : 3.6 : 1).

Vulcanization of crepe rubber by sulfur monochloride. Part I. The gelation method

AbstractWhen a solution of natural rubber hydrocarbon is cold vulcanized with sulfur monochloride, a gel is formed. The rate of gel formation is used to characterize the rate of reaction between rubber and sulfur monochloride and a preliminary kinetic investigation is described. It is shown that the reaction is accelerated by compounds normally used for speeding up sulfur (hot) vulcanization, and it is suggested that these function by virtue of their possessing an active hydrogen atom. Several series of simple compounds, containing the groups SH, OH, and NH2, are shown to function as effective accelerators and their activity is attributed to the presence of a labile hydrogen atom in the molecule RXH, where R = organic radical and X = S, O, or N. The absence of a direct relationship between accelerating power and basic or acidic strength suggests a free radical mechanism of accelerator action, based upon the process ${\rm R} - {\rm X} - {\rm H } \to {\rm R} - \mathop {{\rm X }}\limits^ * {\rm + }\mathop {{\rm H }}\limits^ * $.