Homogeneous solution synthesis

The aforementioned process has the advantage of being a homogeneous solution synthesis as well as the advantage of the heterogeneous purification. 

For reactions carried out in homogeneous solution or under solid-phase conditions the use of Fmoc amino acid chlorides is limited by the competition between their aminolysis and the formation of the less reactive oxazol-5(4//)-ones in the presence of tertiary amines, which are essential components of such reaction systems. To improve the results under these conditions a hindered base, e.g. 2,6-di-/er/-butylpyridine, can be used as a hydrogen chloride acceptor since conversion to oxazol-5(4//)-one is slow with such bases. Although shown to be advantageous in certain cases, Fmoc amino acid chlorides are used in homogeneous solution synthesis only in particular cases. They react efficiently in the presence of pyridine with weak nucleophiles such as imine 2P l (Scheme 2) where other activated species such as an active ester, anhydride, acyl fluoride, and acyl imidazolide fail. 

Soluble support-based synthetic approaches offer the advantages of both homogeneous solution-phase chemistry (high reactivity, ease of analysis) and solid-phase synthesis (large excess of reagents, simple product isolation and purification) [98,99]. As a representative example, PEG, one of the most widely used soluble polymers, has good solubility in most organic solvents (i.e., dichloromethane, acetonitrile, dimethylformamide, and toluene), but it... 

To understand a heterogeneous synthesis process, the following preliminary experiments were performed in a homogeneous solution (1) In the absence of zeolite, the sonochemical reduction of [Pd(NH3)4]2+ to Pd° was found to occur, but the rate of [Pd(NH3)4]2+reduction was much slower than that of [PdCL(]2 reduc-tion. (2) It was confirmed that 2-propanol acted as a precursor to form reductants under ultrasonic irradiation. 

In the specific case of silica nanoparticles-pH EMA hybrid materials, the synthesis relies on obtaining a fine dispersion of silica nanoparticles (with a mean diameter of 7nm) in HEMA monomers (liquid phase). When a homogeneous solution is obtained, a free radical initiator is added at a concentration based on the weight of the monomer mixture. After the initiator dissolution, the solution can be poured into molds or between two glass plates to obtain monoliths or uniform films, respectively, after being cured at temperatures around 60-85 °C for several hours. 

SN2 reactions of primary organolithium compounds on PMMA in dilute homogeneous solution may be considered as a model system where all the important reaction parameters may be controlled they allow both a quantitative analysis of PMMA chain reactivity and the synthesis of well defined ketonic copolymers within a wide range of possible structural variations. The two homologous series of organolithium compounds and the corresponding reaction conditions we selected are given below ... 

Initially, the term Hquid-phase synthesis was used to contrast the differences between soHd-phase peptide synthesis and a method of synthesis on soluble polyethylene glycol (PEG) [5, 6]. Although soluble polymer-supported synthesis is less ambiguous than Hquid-phase synthesis, the latter term is more prevalent in the Hterature. In-keeping with previous reviews [7-12], the phrases classical or solution synthesis will be used to describe homogeneous reaction schemes that do not employ polymer supports while liquid-phase synthesis will be reserved... 

Oxidative nitration, a process discovered by Kaplan and Shechter, is probably the most efficient and useful method available for the synthesis of em-dinitroaliphatic compounds from the corresponding nitroalkanes. The process, which is an electron-transfer substitution at saturated carbon, involves treatment of the nitronate salts of primary or secondary nitroalkanes with silver nitrate and an inorganic nitrite in neutral or alkali media. The reaction is believed ° °° to proceed through the addition complex (82) which collapses and leads to oxidative addition of nitrite anion to the nitronate and reduction of silver from Ag+ to Ag . Reactions proceed rapidly in homogeneous solution between 0 and 30 °C. 

Matijevic, E. Partsch, R.E. (2000) Synthesis of monodispersed colloids by chemical reactions. In Sugimoto.T. (ed.) Fine Particles Synthesis, Characterization and Mechanism of Growth. Marcel Dekker, New York Matijevic, E. Sapieszko, R.S. (2000) Forced hydrolysis in homogeneous solutions. In Sugi-moto, T. (ed.) Fine Particles. Basel, Marcel Dekker, 2-34... 

This method involves formation of reverse micelles in the presence of surfactants at a water-oil interface. A clear homogeneous solution obtained by the addition of another amine or alcohol-based cosurfactant is termed a Microemulsion. To a reverse micelle solution containing a dissolved metal salt, a second reverse micelle solution containing a suitable reducing agent is added reducing the metal cations to metals. The synthesis of oxides from reverse micelles depends on the coprecipitation of one or more metal ions from... 

Scheme 12 The Fragment Synthesis of Human Midkine in Homogeneous Solution in a Mixture of Chloroform and Trifluoroethanoll44 Boc—(1-11) —OPac I Boc—(12-22)—OPac II Boc—(23-31)—OPac III Boc—(32-40)—OPac IV Boc—(41-51)—OPac V Boc—(52-59)—OPac VI...

REACTION IN HOMOGENEOUS SOLUTIONS FOR THE SYNTHESIS OF METAL PHOSPHATE PARTICLES... 

When we consider the metals of nanoscopic size, fine metal particles from micrometer to nanometer size can be synthesized by both physical and chemical methods. The former method provides the fine metal particles by decreasing the size by addition of energy to the bulk metal, while in the latter methods, fine particles can be produced by increasing the size from metal atoms obtained by reduction of metal ions in solution. Since chemical reactions usually take place in homogeneous solution in any case, this chapter includes most of the cases of synthesis and growth of fine metal particles. However, the polyol process, reaction in microemulsions, and formation in the gas phase are omitted, since they are described in later chapters by specialists in those fields. 

Synthesis of Fine Metal Particles in Homogeneous Solution... 

This section is concerned with the mechanism of formation and growth of metal nanoparticles in homogeneous solutions. As mentioned in the section on synthesis of metal nanoparticles, there are many kinds of synthetic methods. Each method has its own process and mechanism. However, there are four main processes ... 

Product precipitated from a reaction in solution A homogeneous solution from which the product precipitates. These systems have been used for peptide synthesis since the 1930s. 

Based on the original Stoeber synthesis which leads to nonporous silica particles we developed a novel route to synthesize mesoporous silica particles. All syntheses were carried out in an homogeneous solution of alcohol/water/ammonia. To control the porosity of the obtained particles, polymers were used as templates. 

Early attempts showed that during the synthesis of TV-alkyl amino acid derivatives by routes a or b in homogenous solution the following problems must be solved ... 

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