Reaction with another solid phase

In the first four cases sohd products are formed, so that the original particles are replaced with another solid phase. In the fifth reaction the solid phase... 

The general setup for trapping a reaction intermediate is shown in Scheme 11-1. The solid phase (I) (resin precursor) can be activated by a suitable reaction to give the low-molecular-weight reaction intermediate, which is soluble and can pass into the liquid phase (solvent). The liquid phase is also in contact with another solid phase (II) (resin trap) so that the reaction intermediate reacts at once with the second resin to give an adduct. The trapped intermediate can either be identified on the resin itself or after cleaving it from the resin. This three-phase approach is best illustrated by the following examples. 

Reactions of the solid with another solid phase are also encoimtered. We consider an interface between the solid and another solid containing the common element B. 

The second step introduces the side chain group by nucleophilic displacement of the bromide (as a resin-bound a-bromoacetamide) with an excess of primary amine. Because there is such diversity in reactivity among candidate amine submonomers, high concentrations of the amine are typically used ( l-2 M) in a polar aprotic solvent (e.g. DMSO, NMP or DMF). This 8 2 reaction is really a mono-alkylation of a primary amine, a reaction that is typically complicated by over-alkylation when amines are alkylated with halides in solution. However, since the reactive bromoacetamide is immobilized to the solid support, any over-alkyla-tion side-products would be the result of a cross-reaction with another immobilized oligomer (slow) in preference to reaction with an amine in solution at high concentration (fast). Thus, in the sub-monomer method, the solid phase serves not only to enable a rapid reaction work-up, but also to isolate reactive sites from... 

Another solid phase fragment condensation with CDI and 1-hydroxybenzotriazole in the synthesis of the human insulin B-chain afforded the oligopeptide in 75% yield. The reaction time with the coupling pair CDI/HOBt was shorter than in the case of the DCC/ HOBt system.136 The CDI/HOBt activation method was also applied to the synthesis of a... 

Another method of segregating and removing a portion of the dissolved organic matter includes incorporation into a solid phase, which can then be removed by filtration or centrifugation. This incorporation can result either from coprecipitation with a solid phase formed in a reaction in the solution or, as discussed in the next section, from adsorption of the organic material onto a pre-existing solid phase. 

Gallop et al. [80] reported the preparation of p-lactams via a [2+2] cycloaddition reaction of ketenes with resin-bound imines derived from amino acids (Scheme 9). This is another solid-phase adaptation of the Staudinger reaction, which could lead to the synthesis of structurally diverse 3,4-bis-substituted 2-azetidinones [81]. In addition, a novel approach to the synthesis of A-unsubstituted-p-lactams, important building blocks for the preparation of p-lactam antibiotics, and useful precursors of chiral p-amino acids was described [82]. 

This reaction is an example of a heterogeneous reaction with a solid catalyst with one reactant principally in solution and another in the gas phase the gas-liquid-solid mixture has to be mixed thoroughly to promote conversion (see Chapter 5 for more detailed consideration of multiphase reactions). Compared with the examples above, the measurement of the hydrogen uptake delivers an additional signal, which can also be used for the determination of reaction parameters. 

Care must be taken to use or determine the correct change of state to which the change of entropy and enthalpy refers. The difficulty arises when one or more equilibrium reactions are present in addition to those used in determining the cell reaction. Such conditions occur when two or more phases are in equilibrium for example, the electrolytic solution may be saturated with a solid phase, or one of the electrodes may consist actually of a liquid solution that is saturated with a solid solution or with another liquid solution. Such equilibria do not alter the change of the Gibbs energy or the emf. Let the cell reaction be represented as v,Bj and an equilibrium reaction as... 

The direct preparation of arylboronic esters from aryl halides or triflates now allows a one-pot, two-step procedure for the synthesis of unsymmetrical biaryls. The synthesis of biaryls was readily carried out in the same flask when the first coupling of aryl halide with diboron was followed by the next reaction with another halide or triflate [240]. The protocol offered a direct and efficient method for the synthesis of the boronic ester in the solid-phase that hitherto met with little success using classical methodology (Scheme 44). The solid-phase boronate (106, 107) [243] was quantitatively obtained by treating a polymer-bound haloarene with the diboron. The subsequent coupling with haloarenes furnished various biaryls. The robot synthesis or the parallel synthesis on the surface of resin is the topic of further accounts of the research. 

Consider two-dimensional steady-state mass transfer in the liquid phase external to a solid sphere at high Schmidt numbers. The particle, which contains mobile reactant A, dissolves into the passing fluid stream, where A undergoes nth-order irreversible homogeneous chemical reaction with another reactant in the liquid phase. The flow regime is laminar, and heat effects associated with the reaction are very weak. Boundary layer approximations are invoked to obtain a locally flat description of this problem. 

Two types of heterogeneous catalysis are most frequently encountered in nature, namely, processes in which the catalyst is in the liquid or solid phase and the reactant is in another immiscible liquid, solid, or gaseous phase, and interfacial processes in which catalysts and substrate are soluble in one phase, but catalytic reactions take place at the interface with another immiscible phase. 

A phase transformation occurs when one material changes its composition or structure. The transformation can be caused by a change in temperature so that no other material is involved or it may involve the reaction with another material, which may or may not be a ceramic, and may be in the liquid or gaseous phase. In this chapter, we will restrict the discussion to phase transformations in which the ceramic is in the solid state. Whenever a phase transformation occurs, a phase boundary must move. 

The peritectic reaction is another invariant reaction involving three phases at equilibrium. With this reaction, upon heating, one solid phase transforms into a liquid phase and another solid phase. A peritectic exists for the copper-zinc system (Figure 9.21, point P) at 598°C (1108°F) and 78.6 wt% Zn-21.4 wt% Cu this reaction is as follows ... 

A doping agent can be introduced by reaction of the considered sohd with another solid, liquid, or gas phase containing the foreign element to be introduced. 

As with solid phase decompositions (Sect. 1), the kinetic characteristics of solid—solid interactions are controlled by the properties of lattice imperfections, though here many systems of interest involve the migration, in a crystal bulk of a mobile participant, from one interface to another. Kinetic measurements have been determined for reactions in a number of favourable systems, but there remain many possibilities for development in a field that is at present so largely unexplored. 

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