Intermediate, unstable

The classification of possible regimes of flow are proposed. It is based on a non-dimensional parameter accounting for the ratio of the micro-channel length to the capillary height. It is shown that in the generic case the governing system of equations, which describes capillary flow, has three stationary solutions two stable and one (intermediate) unstable. 

Cyanogen azide reacts with olefins at 0-35° to afford alkyl-idene cyanamides and/or N-cyanoaziridines arising from decomposition of an intermediate unstable triazoline. 54 With norbomadiene the isolated product is N-cyano-3-azatricyclo-[3.2.1.0s-4-M<,]oct-6-ene (58) which is unstable and rearranges into N-cyano-2-azabicycIo[3.2.1]octa-3,6-diene (59).167... 

Stilbenes and associated molecules provide very good examples of the formation of intermediate unstable isomers which give a chemical route for internal conversion. Upon irradiation, stilbenes undergo a cis-trans isomerization as the predominant reaction. However, under oxidative conditions phenanthrene is also formed.12 It was shown that the phenanthrene came only from c/s-stilbene (13),61 and that an intermediate unstable isomer, nms-dihydrophenanthrene (14), was the precursor of the phenanthrene.62-64 The dihydrophenarithrene was in its ground state, but vibrationally excited, and was formed by a process calculated to be endothermic by 33 10 kcal/mole-1.02 Oxygen or other oxidants converted it to phenanthrene (15), but in the absence of oxidants it was either collisionally stabilized or reverted to m-stilbene. 

The heteroaromatic A-oxides have been the subject of more recent investigation. The structure of the photoproduct appears to be dependent on a number of factors including the nature of the hetero-cycle and its substituents, and the solvent employed in the photolysis. The product can almost always be interpreted as arising via an intermediate unstable oxaziridine, but in no instance has this been isolated. 

The oxidation of selenide 55 with subsequent thermolysis of the intermediate, unstable selenoxide yielded 4-methylene-l,3,2-dioxathiolane A-oxide 56 (28%), which is a synthetic equivalent of allene oxides (Scheme 17) <1999T10845>. 

The fractional value for n—i.e., the apparent order of reaction—is probably due to the complex nature of the competing reactions and the instability of the intermediates. In other words, the mechanism and the kinetics of ozone decomposition in aqueous solution and the possible intermediate unstable ozonide-ring leading from cyanide to cyanate will affect the apparent order of reaction. 

The ease of reversal of alkene insertion is evident from the numerous syntheses of transition metal-hydride complexes using main group metal alkyls as the source of hydride. The hydride in the products of such reactions usually arises from -hydride abstraction or elimination from intermediate unstable transition metal alkyls. This idea is reinforced by the greater effectiveness of secondary alkyls such as isopropyl or cyclohexyl compounds. However, it has been shown that in at least one case the hydride results from hydrolysis of a Pt-Mg bond, not from the alkyl formed from reaction of a Pt-Cl bond with a Grignard reagent. Several of the reactions listed in Table 1 are spontaneously reversible. Reactions where -hydride elimination has been used in the synthesis of hydrides are listed in Table... 

When acetylene is exploded with less than an equimolar volume of oxygen present, a portion of the acetylene is burnt to carbon monoxide and hydrogen presumably through the intermediate, unstable C2H2Oa molecule and the remainder decomposed to carbon and hydrogen. Thus ... 

Palladium nanoparticies can be easily prepared by displacement of the dba ligands by CO from Pd(dba)2. An intermediate unstable carbonyl complex forms, which collapses into clusters. By this method, palladium nanoparticies of sizes in the range 2-5 nm could be obtained using PVP or cellulose derivatives as stabilizers. Such particles were recently used to probe the mechanism of the Heck reaction. A correlation between the initial reaction rate and the particle sizes was established. The small particles proved more active in agreement with the presence of more surface palladium atoms with low metal-metal coordination number. ... 

Ligogenicity manifests in the formation of additional o bonds in excited states (high-energy molecular species), intermediates (unstable ground-state molecular species) or products (stable groimd-state molecular species). 

The second mechanism of oxygen evolution on metal oxides can be expressed by the general eqnations given below. First, H2O is decomposed forming an intermediate unstable oxide [108] ... 

Intermediate, unstable forms are critical for the layer quality, because they have influence on the bonding quality of the metal-substrate connection. A system can be random in a short term and deterministic in a long term. 

Composition measurements in flames are generally considered under two categories—stable and unstable. Stable species are those which are stable to sampling and ordinary analytical techniques. This includes the major species, fuel, oxidizer, products, and many intermediate. Unstable species are those which are not stable to normal sampling and analytical techniques. They include... 

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