Intermediate stage reaction

Refers to the elapsed time after an adhesive is applied until pressure effects curing. Intermediate-stage reaction step for various thermosetting resins. During this stage the material swells when in contact with certain liquids and... 

Figure 5.5. Diagram of energy profile (dotted line) as molecular oxygen reacts with a surface of carbon to form surface oxygen complexes, carbon monoxide, and carbon dioxide. describes activation energies of intermediate stage reactions.

In a sense the formation of t) -H2 complexes can be thought of as an intermediate stage in the oxidative addition of H2 to form two M-H bonds and, as such, the complexes might serve as a model for this process and for catalytic hydrogenation reactions by metal hydrides. Indeed, intermediate cases between and... 

The sulfonylation mechanism involves a two-stage reaction, as shown in Scheme 6.4. The sulfonylium cation ArS02+ attacks the carbon on the aromatic nucleus to generate an intermediate complex, which subsequently decomposes to afford the final product by eliminating a proton. It is postulated that the effective sulfonylating agent is the sulfonylium salt generated by action of the Lewis-acid catalyst on the sulfonyl halide.18... 

In this book the discussion has been restricted to the structure of the normal states of molecules, with little reference to the great part of chemistry dealing with the mechanisms and rates of chemical reactions. It seems probable that the concept of resonance can be applied very effectively in this field. The activated complexes which represent intermediate stages in chemical reactions are, almost without exception, unstable molecules which resonate among several valence-bond structures. Thus, according to the theory of Lewis, Olson, and Polanyi, Walden inversion occurs in the hydrolysis of an alkyl halide by the following mechanism ... 

Many molecules undergo partial oxidation on adsorption and many alkanes and alkenes are believed to yield an adsorbed CHO group on adsorption (Petrii, 1968). These processes usually lead to the complete oxidation of the organic molecule to carbon dioxide and few workers have attempted to halt the reaction at an intermediate stage. Hence, although there are undoubtedly possibilities for using dissociative chemisorption for synthetic reactions, this chapter will not consider these processes further. 

Fig. 10. Concentration curves fitted by exponential regression for the reaction of l,2,4,5r tetrabromobenzene (A) with surface bound chloride, a consecutive four-stage reaction with three intermediates (B,C,D) and the product E.

Thermal reactions of the second type, which do not involve adding ligands toward formation of metal organic product compounds, are less widely recognized as chemical phenomena. There may be here a simple failure of reaction, as in Eq. (16), because (99) of the diffusion of CO from the reaction site there may be stabilization of an intermediate stage by scavenger action (26, 27, 56) ... 

In this case, we have given both the starting conditions and those of the intermediate stage of solid state reaction. It should be clear that A reacts with B, and vice versa. Thus, a phase boundary is formed at the interface of the bulk of each particle, i.e.- between A and AB, and between B and AB. The phase boundary, AB, then grows outward as shown above. Once the phase boundary is established, then each reacting specie must diffuse through the phase AB to reach its opposite phase boundary in order to react. That is- A must difiuse through AB to the phase boundary... 

When a number of competing reactions are involved in a process, and/or when the desired product is obtained at an intermediate stage of a reaction, it is important to keep the residence-time distribution in a reactor as narrow as possible. Usually, a broadening of the residence-time distribution results in a decrease in selectivity for the desired product. Hence, in addition to the pressure drop, the width of the residence-time distribution is an important figure characterizing the performance of a reactor. In order to estimate the axial dispersion in the fixed-bed reactor, the model of Doraiswamy and Sharma was used [117]. This model proposes a relationship between the dispersive Peclet number ... 

Ketones can be converted to nitriles by the following sequence of reagents. Indicate the intermediate stages of the reaction. 

Figure 4.2 Intermediate stage of the reaction with c(2 x 4)-0 structure on Rh(l 1 0) (a) zoom on the surface behind the reaction front. Dimensions 11.5 nm x 7.5 nm. 1= 1 nA,...

The reaction L" + 02" —> LHOCT leads, after some intermediate stages, to generation of electronically excited compound AP (aminophthalate anion) [23, 24], In these reactions, let kj = 31k2, but at pH = 9.2 both proceed equally fast. 

The problem of competition of the molecular reaction (direct route) and chain reaction (complicated, multistage route) was firstly considered in the monograph by Semenov [1], The new aspect of this problem appeared recently because the quantum chemistry formulated the rule of conservation of orbital symmetry in chemical and photochemical reactions (Woodward-Hofmann rule [4]). Very often the structure of initial reactants suggests their direct interaction to form the same final products, which are also obtained in the chain reaction, and the thermodynamics does not forbid the reaction with AG < 0. However, the experiment often shows that many reactions of this type occur in a complicated manner through several intermediate stages. For example, the reaction... 

Uptake of CO (1 atm. CO, 50°C, 12 h, or 9.5 atm. CO, roan temp., 40 h) by the decarbonylated resins was sluggish under conditions comparable to the complete regeneration of CpCo(C0)2 from clusters (33), only 20% regeneration of 3 and 5 was detected by IR. Quantitative recarbonylation (IR spectrum) was achieved by using 100-110 atm. CO, 200°C, benzene solvent for 24 h. No new carbonyl bearing species were detected at intermediate stages of this reaction. The strenuous conditions are necessary, as a reaction for 18 h yielded only 92% reconversion. Minimal cobalt loss fran the resin had occurred by this drastic treatment (elemental analysis). 

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